[Page ii][Illustration: THE CONSTELLATIONS OF ORION AND TAURUS. NOTES. --Star a in Taurus is red, has eight metals; moves east (page227). At o above tip of right horn is the Crab Nebula (page 219). In Orion, a is variable, has five metals; recedes 22 miles persecond. B, d, e, x, r, etc. , are double stars, the component partsof various colors and magnitudes (page 212, note). L and i aretriple; s, octuple; th, multiple, surrounded by a fine Nebula (page218). ] [Page iii]RECREATIONS IN ASTRONOMY WITH _DIRECTIONS FOR PRACTICAL EXPERIMENTS AND TELESCOPIC WORK_ BY HENRY WHITE WARREN, D. D. AUTHOR OF "SIGHTS AND INSIGHTS; OR, KNOWLEDGE BY TRAVEL, " ETC. WITH EIGHTY-THREE ILLUSTRATIONS AND MAPS OF STARS [Page v][Greek: TAEI PSUCHAEI TAEI AGAPAETAEI ASTRAPOUSAEI KAI ISAGGEDOI] [Page vii]PREFACE. All sciences are making an advance, but Astronomy is moving at thedouble-quick. Since the principles of this science were settledby Copernicus, four hundred years ago, it has never had to beata retreat. It is rewritten not to correct material errors, butto incorporate new discoveries. Once Astronomy treated mostly of tides, seasons, and telescopicaspects of the planets; now these are only primary matters. Onceit considered stars as mere fixed points of light; now it studiesthem as suns, determines their age, size, color, movements, chemicalconstitution, and the revolution of their planets. Once it consideredspace as empty; now it knows that every cubic inch of it quivers withgreater intensity of force than that which is visible in Niagara. Every inch of surface that can be conceived of between suns is morewave-tossed than the ocean in a storm. The invention of the telescope constituted one era in Astronomy;its perfection in our day, another; and the discoveries of thespectroscope a third--no less important than either of the others. While nearly all men are prevented from practical experimentationin these high realms of knowledge, few [Page viii] have so littleleisure as to be debarred from intelligently enjoying the resultsof the investigations of others. This book has been written not only to reveal some of the highestachievements of the human mind, but also to let the heavens declarethe glory of the Divine Mind. In the author's judgment, there is nogulf that separates science and religion, nor any conflict wherethey stand together. And it is fervently hoped that anyone whocomes to a better knowledge of God's works through reading thisbook, may thereby come to a more intimate knowledge of the Worker. I take great pleasure in acknowledging my indebtedness to J. M. Van Vleck, LL. D. , of the U. S. Nautical Almanac staff, and Professorof Astronomy at the Wesleyan University, for inspecting some of themore important chapters; to Dr. S. S. White, of Philadelphia, fortelescopic advantages; to Professor Henry Draper, for furnishing, in advance of publication, a photograph of the sun's corona in 1878;and to the excellent work on "Popular Astronomy, " by ProfessorSimon Newcomb, LL. D. , Professor U. S. Naval Observatory, for someof the most recent information, and for the use of the unequalledengravings of Jupiter, Saturn, and the great nebula of Orion. [Page ix]CONTENTS. CHAP. I. CREATIVE PROCESSES II. CREATIVE PROGRESS Constitution of Light Chemistry of Suns revealed by Light Creative Force of Light III. ASTRONOMICAL INSTRUMENTS The Telescope The Reflecting Telescope The Spectroscope IV. CELESTIAL MEASUREMENTS Celestial Movements How to Measure V. THE SUN What the Sun does for us VI. THE PLANETS, AS SEEN FROM SPACE The Outlook from the Earth VII. SHOOTING-STARS, METEORS, AND COMETS Aerolites Comets Famous Comets Of what do Comets consist? Will Comets strike the Earth? VIII. THE PLANETS AS INDIVIDUALS Vulcan Mercury Venus The Earth The Aurora Borealis[Page x] The Delicate Balance of Forces Tides The Moon Telescopic Appearance Eclipses Mars Satellites of Mars Asteroids Jupiter Satellites of Jupiter Saturn Rings of Saturn Satellites of Saturn Uranus Neptune IX. THE NEBULAR HYPOTHESIS. X. THE STELLAR SYSTEM The Open Page of the Heavens Equatorial Constellations Characteristics of the Stars Number Double and Multiple Stars Colored Stars Clusters of Stars Nebulæ Variable Stars Temporary, New, and Lost Stars Movements of Stars XI. THE WORLDS AND THE WORD XII. THE ULTIMATE FORCE SUMMARY OF LATEST DISCOVERIES AND CONCLUSIONS SOME ELEMENTS OF THE SOLAR SYSTEM EXPLANATION OF ASTRONOMICAL SYMBOLS Signs of the Zodiac Other Abbreviations Used in the Almanac Greek Alphabet Used Indicating the Stars CHAUTAUQUA OUTLINE FOR STUDENTS GLOSSARY OF ASTRONOMICAL TERMS AND INDEX [Page xi]ILLUSTRATIONS FIG. The Constellations of Orion and Taurus 1. An Orbit resulting from Attraction and Projection 2. The Moon's Orbit about the Earth 3. Changes of Orbit by Mutual Attraction 4. Velocity of Light measured by Jupiter's Satellites 5. Velocity of Light measured by Fizeau's Toothed Wheel 6. White Light resolved into Colors 7. Showing amount of Light received by Different Planets 8. Measuring Intensities of Lights 9. Reflection and Diffusion of Light 10. Manifold Reflections 11. Refraction by Water 12. Atmospherical Reflection 13. Refracting Telescope 14. Reflecting Telescope 15. The Cambridge Equatorial Refractor 16. The new Reflecting Telescope at Paris 17. Spectroscope, with Battery of Prisms 18. Spectra of Glowing Hydrogen and of the Sun 19. Illustrating Arcs and Angles 20. Measuring Objects by observing Angles 21. Mural Circle 22. Scale to measure Hundredths of an Inch 23. Spider-lines to determine Star Transits 24. Illustrating Triangulation[Page xii] 25. Measuring Distance to an Inaccessible Object 26. Measuring Elevation of an Inaccessible Object 27. Illustrating Parallax 28. Illustrating Stellar Parallax 29. Mode of Ascertaining Longitude 30. Relative Size of Sun, as seen from Different Planets 31. Zodiacal Light 32. Corona of the Sun in 1858--Brazil 33. Corona of the Sun in 1878--Colorado 34. Solar Prominences of Flaming Hydrogen 35. Changes in Solar Cavities during Rotation 36. Solar Spot 37. Holding Telescope to see the Sun-spots 38. Orbits and Comparative Sizes of the Planets 39. Orbit of Earth, illustrating Seasons 40. Inclination of Planes of Planetary Orbits 41. Inclination of Orbits of Earth and Venus 42. Showing the Sun's Movement among the Stars 43. Passage of the Sun by Star Regulus 44. Apparent Path of Jupiter among the Stars 45. Illustrating Position of Planets 46. Apparent Movements of an Inferior Planet 47. Apparent Movements of a Superior Planet 47_a_. A Swarm of Meteors meeting the Earth 48. Explosion of a Bolide 49. Flight of Bolides 50. The Santa Rosa Aerolite 51. Orbit of November Meteors and the Comet of 1866 52. Aspects of Remarkable Comets 53. Phases and Apparent Dimensions of Venus 54. The Earth and Moon in Space 55. Aurora as Waving Curtains 56. Tide resulting from Centrifugal Motion 57. Lunar Landscape[Page xiii] 58. Telescopic View of the Moon 59. Illumination of Lunar Craters and Peaks 60. Lunar Crater "Copernicus" 61. Eclipses: Shadows of Earth and Moon 62. Apparent Sizes of Mars, seen from the Earth 63. Jupiter 64. Various Positions of Jupiter's Satellites 65. View of Saturn and his Rings 66. Perturbations of Uranus 67. Map: Circumpolar Constellations 68. Map of Constellations on the Meridian in December 69. Map of Constellations on the Meridian in January 70. Map of Constellations on the Meridian in April 71. Map of Constellations on the Meridian in June 72. Map of Constellations on the Meridian in September 73. Map of Constellations on the Meridian in November 74. Southern Circumpolar Constellations 75. Aspects of Double Stars 76. Sprayed Star Cluster below ae in Hercules 77. Globular Star Cluster in the Centaur 78. Great Nebula about th Orionis 79. The Crab Nebula above z Tauri 80. The Ring Nebula in Lyra 81. Showing Place of Ring Nebula 82. The Horizontal Pendulum COLORED PLATE REPRESENTING VARIOUS SPECTA MAPS TO FIND THE STARS [Page 1]I. CREATIVE PROCESSES. "In the beginning God created the heaven and the earth. And the earth was without form, and void; and darkness was upon the face of the deep. "--_Genesis_ i. 1, 2. [Page 2] "Not to the domes, where crumbling arch and column Attest the feebleness of mortal hand, But to that fane, most catholic and solemn, Which God hath planned, -- To that cathedral, boundless as our wonder, Whose quenchless lamps the sun and stars supply; Its choir the winds and waves, its organ thunder, Its dome the sky. " H. W. LONGFELLOW. "The heavens are a point from the pen of His perfection; The world is a rose-bud from the bower of His beauty; The sun is a spark from the light of His wisdom; And the sky a bubble on the sea of His power. " SIR W. JONES. [Page 3]RECREATIONS IN ASTRONOMY. * * * * * I. _CREATIVE PROCESSES. _ During all the ages there has been one bright and glittering pageof loftiest wisdom unrolled before the eye of man. That this pagemay be read in every part, man's whole world turns him before it. This motion apparently changes the eternally stable stars into amoving panorama, but it is only so in appearance. The sky is avast, immovable dial-plate of "that clock whose pendulum ticksages instead of seconds, " and whose time is eternity. The moonmoves among the illuminated figures, traversing the dial quickly, like a second-hand, once a month. The sun, like a minute-hand, goesover the dial once a year. Various planets stand for hour-hands, moving over the dial in various periods reaching up to one hundredand sixty-four years; while the earth, like a ship of exploration, sails the infinite azure, bearing the observers to different pointswhere they may investigate the infinite problems of this mightymachinery. This dial not only shows present movements, but it keeps the historyof uncounted ages past ready to be [Page 4] read backward in properorder; and it has glorious volumes of prophecy, revealing thefar-off future to any man who is able to look thereon, break theseals, and read the record. Glowing stars are the alphabet of thislofty page. They combine to form words. Meteors, rainbows, auroras, shifting groups of stars, make pictures vast and significant as thearmies, angels, and falling stars in the Revelation of St. John--changing and progressive pictures of infinite wisdom andpower. Men have not yet advanced as far as those who saw the pictures Johndescribes, and hence the panorama is not understood. That continuousspeech that day after day uttereth is not heard; the knowledge thatnight after night showeth is not seen; and the invisible thingsof God from the creation of the world, even his eternal power andGodhead, clearly discoverable from things that are made, are notapprehended. The greatest triumphs of men's minds have been in astronomy--andever must be. We have not learned its alphabet yet. We read onlyeasy lessons, with as many mistakes as happy guesses. But in time weshall know all the letters, become familiar with the combinations, be apt at their interpretation, and will read with facility thelessons of wisdom and power that are written on the earth, blazonedin the skies, and pictured by the flowers below and the rainbowsabove. In order to know how worlds move and develop, we must create them;we must go back to their beginning, give their endowment of forces, and study the laws of their unfolding. This we can easily do by thatfaculty wherein man is likest his Father, a creative imagination. God creates and embodies; we create, but [Page 5] it remains inthought only. But the creation is as bright, strong, clear, enduring, and real, as if it were embodied. Every one of us wouldmake worlds enough to crush us, if we could embody as well ascreate. Our ambition would outrun our wisdom. Let us come into thehigh and ecstatic frame of mind which Shakspeare calls frenzy, inthe exigencies of his verse, when "The poet's eye, in a fine frenzy rolling, Doth glance from heaven to earth, from earth to heaven; And, as imagination bodies forth The forms of things unknown, the poet's pen Turns them to shapes, and gives to airy nothing A local habitation and a name. " In the supremacy of our creative imagination let us make emptyspace, in order that we may therein build up a new universe. Let uswave the wand of our power, so that all created things disappear. There is no world under our feet, no radiant clouds, no blazingsun, no silver moon, nor twinkling stars. We look up, there isno light; down, through immeasurable abysses, there is no form;all about, and there is no sound or sign of being--nothing saveutter silence, utter darkness. It cannot be endured. Creation isa necessity of mind--even of the Divine mind. We will now, by imagination, create a monster world, every atomof which shall be dowered with the single power of attraction. Every particle shall reach out its friendly hand, and there shallbe a drawing together of every particle in existence. The lawsgoverning this attraction shall be two. When these particles areassociated together, the attraction shall be in proportion to themass. A given mass will pull twice [Page 6] as much as one of halfthe size, because there is twice as much to pull. And a given masswill be pulled twice as much as one half as large, because there istwice as much to be pulled. A man who weighed one hundred and fiftypounds on the earth might weigh a ton and a half on a body as largeas the sun. That shall be one law of attraction; and the other shallbe that masses attract inversely as the square of distances betweenthem. Absence shall affect friendships that have a material basis. If a body like the earth pulls a man one hundred and fifty pounds atthe surface, or four thousand miles from the centre, it will pullthe same man one-fourth as much at twice the distance, one-sixteenthas much at four times the distance. That is, he will weigh by aspring balance thirty-seven and a half pounds at eight thousandmiles from the centre, and nine pounds six ounces at sixteenthousand miles from the centre, and he will weigh or be pulled bythe earth 1/24 of a pound at the distance of the moon. But the moonwould be large enough and near enough to pull twenty-four pounds onthe same man, so the earth could not draw him away. Thus the twolaws of attraction of gravitation are--1, _Gravity is proportionedto the quantity of matter_; and 2, _The force of gravity variesinversely as the square of the distance from the centre of theattracting body_. The original form of matter is gas. Almost as I write comes theannouncement that Mr. Lockyer has proved that all the so-calledprimary elements of matter are only so many different sized moleculesof one original substance--hydrogen. Whether that is true or not, let us now create all the hydrogen we can [Page 7] imagine, eitherin differently sized masses or in combination with other substances. There it is! We cannot measure its bulk; we cannot fly around it inany recordable eons of time. It has boundaries, to be sure, for weare finite, but we cannot measure them. Let it alone, now; leave itto itself. What follows? It is dowered simply with attraction. Thevast mass begins to shrink, the outer portions are drawn inward. They rush and swirl in vast cyclones, thousands of miles in extent. The centre grows compact, heat is evolved by impact, as will beexplained in Chapter II. Dull red light begins to look like comingdawn. Centuries go by; contraction goes on; light blazes ininsufferable brightness; tornadoes, whirlpools, and tempestsscarcely signify anything as applied to such tumultuous tossing. There hangs the only world in existence; it hangs in empty space. It has no tendency to rise; none to fall; none to move at all inany direction. It seethes and, flames, and holds itself togetherby attractive power, and that is all the force with which we haveendowed it. Leave it there alone, and withdraw millions of miles into space:it looks smaller and smaller. We lose sight of those distinctivespires of flame, those terrible movements. It only gives an eveneffulgence, a steady unflickering light. Turn one quarter round. Still we see our world, but it is at one side. Now in front, in the utter darkness, suddenly create another worldof the same size, and at the same distance from you. There theystand--two huge, lone bodies, in empty space. But we created themdowered with attraction. Each instantly feels the drawing influenceof the other. They are mutually attractive, and begin to [Page 8]move toward each other. They hasten along an undeviating straightline. Their speed quickens at every mile. The attraction increasesevery moment. They fly swift as thought. They dash their flaming, seething foreheads together. And now we have one world again. It is twice as large as before, that is all the difference. There is no variety, neither any motion;just simple flame, and nothing to be warmed thereby. Are our creativepowers exhausted by this effort? [Illustration: Fig. 1. --Orbit A D, resulting from attraction, AC, and projectile force, A B. ] No, we will create another world, and add another power to it thatshall keep them apart. That power shall be what is called the forceof inertia, which is literally no power at all; it is an inabilityto originate or change motion. If a body is at rest, inertia isthat quality by which it will forever remain so, unless acted uponby some force from without; and if a body is in motion, it willcontinue on at the same speed, in a straight line, forever, unlessit is quickened, retarded, or turned from its path by some otherforce. Suppose our newly created sun is 860, 000 miles in diameter. Go away 92, 500, 000 miles and create an earth eight thousand milesin diameter. It instantly feels the attractive power of the sundrawing it to itself sixty-eight [Page 9] miles a second. Now, justas it starts, give this earth a push in a line at right angles withline of fall to the sun, that shall send it one hundred andeighty-nine miles a second. It obeys both forces. The result is thatthe world moves constantly forward at the same speed by its inertiafrom that first push, and attraction momentarily draws it from itsstraight line, so that the new world circles round the other to thestarting-point. Continuing under the operation of both forces, theworlds can never come together or fly apart. They circle about each other as long as these forces endure; forthe first world does not stand still and the second do all thegoing; both revolve around the centre of gravity common to both. In case the worlds are equal in mass, they will both take the sameorbit around a central stationary point, midway between the two. In case their mass be as one to eighty-one, as in the case of theearth and the moon, the centre of gravity around which both turnwill be 1/81 of the distance from the earth's centre to the moon'scentre. This brings the central point around which both worldsswing just inside the surface of the earth. It is like an appleattached by a string, and swung around the hand; the hand movesa little, the apple very much. Thus the problem of two revolving bodies is readily comprehended. The two bodies lie in easy beds, and swing obedient to constantforces. When another body, however, is introduced, with its varyingattraction, first on one and then on the other, complications areintroduced that only the most masterly minds can follow. Introducea dozen or a million bodies, and complications arise that onlyOmniscience can unravel. [Page 10][Illustration: Fig. 2. ] Let the hand swing an apple by an elastic cord. When the applefalls toward the earth it feels another force besides that derivedfrom the hand, which greatly lengthens the elastic cord. To tearit away from the earth's attraction, and make it rise, requiresadditional force, and hence the string is lengthened; but whenit passes over the hand the earth attracts it downward, and thestring is very much shortened: so the moon, held by an elastic cord, swings around the earth. From its extreme distance from the earth, at A, Fig. 2, it rushes with increasing speed nearly a quarter of amillion of miles toward the sun, feeling its attraction increasewith every mile until it reaches B; then it is retarded in itsspeed, by the same attraction, as it climbs back its quarter ofa million of miles away from the sun, in defiance of its power, to C. All the while the invisible elastic force of the earth isunweariedly maintained; and though the moon's distances vary over arange of 31, 355 miles, the moon is always in a determinable place. A simple revolution of one world about another in a circular orbitwould be a problem of easy solution. It would always be at thesame distance from its centre, and going with the same velocity. But there are over sixty causes that interfere with such a simpleorbit in the case of the moon, all of which causes and theirdisturbances must be considered in calculating such a simple matteras an eclipse, or predicting the moon's place as the sailors guide. One of the most puzzling of the irregularities [Page 11] of ournight-wandering orb has just been explained by Professor Hansen, ofGotha, as a curious result of the attraction of Venus. [Illustration: Fig. 3. --Changes of orbit by mutual attraction. ] Take a single instance of the perturbations of Jupiter and Saturnwhich can be rendered evident. The times of orbital revolution ofSaturn and Jupiter are nearly as five to two. Suppose the orbits ofthe planets to be, as in Fig. 3, both ellipses, but not necessarilyequally distant in all parts. The planets are as near as possibleat 1, 1. Drawn toward each other by mutual attraction, Jupiter'sorbit bends outward, and Saturn's becomes more nearly straight, asshown by the dotted lines. A partial correction of this difficultyimmediately follows. As Jupiter moves on ahead of Saturn it is heldback--retarded in its orbit by that body; and Saturn is hastenedin its orbit by the attraction of Jupiter. Now greater speed meansa straighter orbit. A rifle-ball flies nearer in a straight linethan a thrown stone. A greater velocity given to a whirled ballpulls the elastic cord far enough to give the ball a larger orbit. Hence, being hastened, Saturn stretches out nearer its proper orbit, and, retarded, Jupiter approaches the smaller curve that is itstrue orbit. But if they were always to meet at this point, as they would ifJupiter made two revolutions to Saturn's one, it would be disastrous. In reality, when Saturn has gone around two-thirds of its orbit to2, Jupiter will have gone once and two-thirds around and overtaken[Page 12] Saturn; and they will be near again, be drawn together, hastened, and retarded, as before; their next conjunction would beat 3, 3, etc. Now, if they always made their conjunction at points equally distant, or at thirds of their orbits, it would cause a series of increasingdeviations; for Jupiter would be constantly swelling his orbit atthree points, and Saturn increasingly contracting his orbit atthe same points. Disaster would be easily foretold. But as theirtimes of orbital revolutions are not exactly in the ratio of fiveand two, their points of conjunction slowly travel around the orbit, till, in a period of nine hundred years, the starting-point isagain reached, and the perturbations have mutually corrected oneanother. For example, the total attractive effect of one planet on the otherfor 450 years is to quicken its speed. The effect for the next 450years is to retard. The place of Saturn, when all the retardationshave accumulated for 450 years, is one degree behind what it iscomputed if they are not considered; and 450 years later it willbe one degree before its computed place--a perturbation of twodegrees. When a bullet is a little heavier or ragged on one side, it will constantly swerve in that direction. The spiral groove inthe rifle, of one turn in forty-five feet, turns the disturbingweight or raggedness from side to side--makes one error correctanother, and so the ball flies straight to the bull's-eye. So theplace of Jupiter and Saturn, though further complicated by fourmoons in the case of Jupiter, and eight in the case of Saturn, andalso by perturbations caused by other planets, can be calculatedwith exceeding nicety. The difficulties would be greatly increased if the orbits [Page 13]of Saturn and Jupiter, instead of being 400, 000, 000 miles apart, were interlaced. Yet there are the orbits of one hundred andninety-two asteroids so interlaced that, if they were made of wire, no one could be lifted without raising the whole net-work of them. Nevertheless, all these swift chariots of the sky race along thecourse of their intermingling tracks as securely as if they wereeach guided by an intelligent mind. _They are guided by anintelligent mind and an almighty arm. _ Still more complicated is the question of the mutual attractions ofall the planets. Lagrange has been able to show, by a mathematicalgenius that seems little short of omniscience in his single departmentof knowledge, that there is a discovered system of oscillations, affecting the entire planetary system, the periods of which areimmensely long. The number of these oscillations is equal to thatof all the planets, and their periods range from 50, 000 to 2, 000, 000years, Looking into the open page of the starry heavens we see doublestars, the constituent parts of which must revolve around a centrecommon to them both, or rush to a common ruin. Eagerly we lookto see if they revolve, and beholding them in the very act, weconclude, not groundlessly, that the same great law of gravitationholds good in distant stellar spaces, and that there the same sufficientmind plans, and the same sufficient power directs and controls allmovements in harmony and security. When we come to the perturbations caused by the mutual attractionsof the sun, nine planets, twenty moons, one hundred and ninety-twoasteroids, millions [Page 14] of comets, and innumerable meteoricbodies swarming in space, and when we add to all these, that belongto one solar system, the attractions of all the systems of the othersuns that sparkle on a brilliant winter night, we are compelled tosay, "As high as the heavens are above the earth, so high above ourthoughts and ways must be the thoughts and ways of Him whocomprehends and directs them all. " [Page 15]II. CREATIVE PROGRESS. "And God said, Let there be light, and there was light. "--_Genesis_ i. , 3. "God is light. "--1 _John_, i. 5. [Page 16] "Hail! holy light, offspring of Heaven first born, Or of the eternal, co-eternal beam, May I express thee unblamed? since God is light, And never but in unapproached light Dwelt from eternity, dwelt then in thee, Bright effluence of bright essence increate. " MILTON. "A million torches lighted by Thy hand Wander unwearied through the blue abyss: They own Thy power, accomplish Thy command, All gay with life, all eloquent with bliss. What shall we call them? Piles of crystal light-- A glorious company of golden streams-- Lamps of celestial ether burning bright-- Suns lighting systems with their joyous beams? But 'Thou to these art as the noon to night. " DERZHAVIN, trans. By BOWRING. [Page 17]II. _CREATIVE PROGRESS. _ Worlds would be very imperfect and useless when simply endowedwith attraction and inertia, if no time were allowed for theseforces to work out their legitimate results. We want somethingmore than swirling seas of attracted gases, something more thancompacted rocks. We look for soil, verdure, a paradise of beauty, animal life, and immortal minds. Let us go on with the process. Light is the child of force, and the child, like its father, is fullof power. We dowered our created world with but a single quality--aforce of attraction. It not only had attraction for its own materialsubstance, but sent out an all-pervasive attraction into space. Bythe force of condensation it flamed like a sun, and not only lightedits own substance, but it filled all space with the luminous outgoingsof its power. A world may be limited, but its influence cannot;its body may have bounds, but its soul is infinite. Everywhere isits manifestation as real, power as effective, presence as actual, as at the central point. He that studies ponderable bodies aloneis not studying the universe, only its skeleton. Skeletons aresomewhat interesting in themselves, but far more so when coveredwith flesh, flushed with beauty, and inspired with soul. Theuniverse [Page 18] has bones, flesh, beauty, soul, and all is one. It can be understood only by a study of all its parts, and bytracing effect to cause. But how can condensation cause light? Power cannot be quiet. Themighty locomotive trembles with its own energy. A smitten pieceof iron has all its infinitesimal atoms set in vehement commotion;they surge back and forth among themselves, like the waves of astorm-blown lake. Heat is a mode of motion. A heated body commencesa vigorous vibration among its particles, and communicates thesevibrations to the surrounding air and ether. When these vibrationsreach 396, 000, 000, 000, 000 per second, the human eye, fitted to beaffected by that number, discerns the emitted undulations, and theobject seems to glow with a dull red light; becoming hotter, thevibrations increase in rapidity. When they reach 765, 000, 000, 000, 000per second the color becomes violet, and the eye can observe them nofarther. Between these numbers are those of different rapidities, which affect the eye--as orange, yellow, green, blue, indigo, in analmost infinite number of shades--according to the sensitivenessof the eye. We now see how our dark immensity of attractive atoms can becomeluminous. A force of compression results in vibrations within, communicated to the ether, discerned by the eye. Illustrations arenumerous. If we suddenly push a piston into a cylinder of brass, the force produces heat enough to set fire to an inflammable substancewithin. Strike a half-inch cube of iron a moderate blow and it becomeswarm; a sufficient blow, and its vibrations become quick enough tobe seen--it is red-hot. Attach a thermometer to an extended [Page19] arm of a whirling wheel; drive it against the air five hundredfeet per second, the mercury rises 16°. The earth goes 98, 000 feetper second, or one thousand miles a minute. If it come to anaerolite or mass of metallic rock, or even a cloudlet of gas, standing still in space, its contact with our air evolves 600, 000°of heat. And when the meteor comes toward the world twenty-six milesa second, the heat would become proportionally greater if the meteorcould abide it, and not be consumed in fervent heat. It vanishesalmost as soon as seen. If there were meteoric masses enough lyingin our path, our sky would blaze with myriads of flashes of light. Enough have been seen to enable a person to read by them at night. If a sufficient number were present, we should miss their individualflashes as they blend their separate fires in one sea ofinsufferable glory. The sun is 1, 300, 000 times as large as ourplanet; its attraction proportionally greater; the aerolites morenumerous; and hence an infinite hail of stones, small masses andlittle worlds, makes ceaseless trails of light, whose individualityis lost in one dazzling sea of glory. On the 1st day of September, 1859, two astronomers, independentlyof each other, saw a sudden brightening on the surface of the sun. Probably two large meteoric masses were travelling side by sideat two or three hundred miles per second, and striking the sun'satmosphere, suddenly blazed into light bright enough to be seenon the intolerable light of the photosphere as a background. Theearth responded to this new cause of brilliance and heat in thesun. Vivid auroras appeared, not only at the north and south poles, but even where such spectacles are seldom seen. The electro-magnetic[Page 20] disturbances were more distinctly marked. "In many placesthe telegraphic wires struck work. In Washington and Philadelphiathe electric signalmen received severe electric shocks; at a stationin Norway the telegraphic apparatus was set fire to; and at Boston aflame of fire followed the pen of Bain's electric telegraph. " Thereis the best of reason for believing that a continuous succession ofsuch bodies might have gone far toward rendering the earthuncomfortable as a place of residence. Of course, the same result of heat and light would follow fromcompression, if a body had the power of contraction in itself. Weendowed every particle of our gas, myriads of miles in extent, with anattraction for every other particle. It immediately compressed itselfinto a light-giving body, which flamed out through the interstellarspaces, flushing all the celestial regions with exuberant light. But heat exerts a repellent force among particles, and soon anequilibrium is reached, for there comes a time when the contractingbody can contract no farther. But heat and light radiate away intocold space, then contraction goes on evolving more light, and sothe suns flame on through the millions of years unquenched. It isestimated that the contraction of our sun, from filling immensityof space to its present size, could not afford heat enough to lastmore than 18, 000, 000 years, and that its contraction from its presentdensity (that of a swamp) to such rock as that of which our earthis composed, could supply heat enough for 17, 000, 000 years longer. But the far-seeing mind of man knows a time must come when thepresent force of attraction [Page 21] shall have produced all theheat it can, and a new force of attraction must be added, or the sunitself will become cold as a cinder, dead as a burned-out char. Since light and heat are the product of such enormous cosmic forces, they must partake of their nature, and be force. So they are. Thesun has long arms, and they are full of unconquerable strengthninety-two millions, or any other number of millions, of milesaway. All this light and heat comes through space that is 200°below zero, through utter darkness, and appears only on the earth. So the gas is darkness in the underground pipes, but light at theburner. So the electric power is unfelt by the cable in the bosomof the deep, but is expressive of thought and feeling at the end. Having found the cause of light, we will commence a study of itsqualities and powers. Light is the astronomer's necessity. When the sublime word wasuttered, "Let there be light!" the study of astronomy was madepossible. Man can gather but little of it with his eye; so he takesa lens twenty-six inches in diameter, and bends all the light thatpasses through it to a focus, then magnifies the image and takesit into his eye. Or he takes a mirror, six feet in diameter, sohollowed in the middle as to reflect all the rays falling upon itto one point, and makes this larger eye fill his own with light. By this larger light-gathering he discerns things for which thelight falling on his pupil one-fifth of an inch in diameter wouldnot be sufficient. We never have seen any sun or stars; we haveonly seen the light that left them fifty minutes or years ago, moreor less. Light is the aërial sprite that carries our measuring-rodsacross the infinite [Page 22] spaces; light spreads out the historyof that far-off beginning; brings us the measure of stars a thousandtimes brighter than our sun; takes up into itself evidences of thevery constitutional elements of the far-off suns, and spreads themat our feet. It is of such capacity that the Divine nature, lookingfor an expression of its own omnipotence, omniscience, and power ofrevelation, was content to say, "God is Light. " We shall need allour delicacy of analysis and measurement when we seek to determinethe activities of matter so fine and near to spirit as light. [Illustration: Fig. 4. --Velocity of Light measured by Eclipses ofJupiter's Moons. ] We first seek the velocity of light. In Fig. 4 the earth is 92, 500, 000miles from the sun at E; Jupiter is 480, 000, 000 miles from the sunat J. It has four moons: the inner one goes around the centralbody in forty-two hours, and is eclipsed at every revolution. Thelight that went out from the sun to M ceases to be reflected backto the earth by the intervention of the planet Jupiter. We knowto a second when these eclipses take place, and they can be seenwith a small telescope. But when the earth is on the opposite sideof the sun [Page 23] from Jupiter, at E', these eclipses at J' takeplace sixteen and a half minutes too late. What is the reason? Isthe celestial chronometry getting deranged? No, indeed; these greatworlds swing never an inch out of place, nor a second out of time. By going to the other side of the sun the earth is 184, 000, 000 milesfarther from Jupiter, and the light that brings the intelligence ofthat eclipse consumes the extra time in going over the extradistance. Divide one by the other and we get the velocity, 185, 000miles per second. That is probably correct to within a thousandmiles. Methods of measurement by the toothed wheel of Fizeau confirmthis result. Suppose the wheel, Fig. 5, to have one thousand teeth, making five revolutions to the second. Five thousand flashes oflight each second will dart out. Let each flash travel nine miles toa mirror and return. If it goes that distance in 1/10000 of asecond, or at the rate of 180, 000 miles a second, the next toothwill have arrived before the eye, and each returning ray be cut off. Hasten the revolutions a little, and the next notch will then admitthe ray, on its return, that went out of each previous notch: theeighteen miles having been traversed meanwhile. The method ofmeasuring by means of a revolving mirror, used by Faucault, is heldto be even more accurate. [Illustration: Fig. 5. --Measuring the Velocity of Light. ] When we take instantaneous photographs by the exposure [Page 24] ofthe sensitive plate 1/20000 part of a second, a stream of light ninemiles long dashes in upon the plate in that very brief period oftime. The highest velocity we can give a rifle-ball is 2000 feet a second, the next second it is only 1500 feet, and soon it comes to rest. We cannot compact force enough behind a bit of lead to keep itflying. But light flies unweariedly and without diminution of speed. When it has come from the sun in eight minutes, Alpha Centauriin three years, Polaris in forty-five years, other stars in onethousand, its wings are in nowise fatigued, nor is the rapidityof its flight slackened in the least. It is not the transactions of to-day that we read in the heavens, but it is history, some of it older than the time of Adam. Thosestars may have been smitten out of existence decades of centuriesago, but their poured-out light is yet flooding the heavens. It goes both ways at once in the same place, without interference. We see the light reflected from the new moon to the earth; reflectedback from the house-tops, fields, and waters of earth, to the moonagain, and from the moon to us once more--three times in oppositedirections, in the same place, without interference, and thus wesee "the old moon in the arms of the new. " _Constitution of Light. _ [Illustration: Fig. 6. --White Light resolved into Colors. ] Light was once supposed to be corpuscular, or consisting of transmittedparticles. It is now known to be the result of undulations in ether. Reference has been made to the minuteness of these undulations. Their velocity is equally wonderful. Put a prism of glass intoa ray of light coming into a dark room, and it is [Page 25]instantly turned out of its course, some parts more and some less, according to the number of vibrations, and appears as the sevencolors on different parts of the screen. Fig. 6 shows thearrangement of colors, and the number of millions of millions ofvibrations per second of each. But the different divisions we callcolors are not colors in themselves at all, but simply a differentnumber of vibrations. Color is all in the eye. Violet has indifferent places from 716 to 765, 000, 000, 000, 000 of vibrations persecond; red has, in different places, from 396 to470, 000, 000, 000, 000 vibrations per second. None of these in anysense are color, but affect the eye differently, and we call thesedifferent effects color. They are simply various velocities ofvibration. An object, like one kind of stripe in our flag, whichabsorbs all kinds of vibrations except those between 396 and470, 000, 000, 000, 000, and reflects those, appears red to us. Thefield for the stars absorbs and destroys all but those vibrationsnumbering about 653, 000, 000, 000, 000 of [Page 25] vibrations persecond. A color is a constant creation. Light makes momentary colorin the flag. Drake might have written, in the continuous present aswell as in the past, "Freedom mingles with its gorgeous dyes The milky baldrick of the skies, And stripes its pore celestial white With streakings of the morning light. " Every little pansy, tender as fancy, pearled with evanescent dew, fresh as a new creation of sunbeams, has power to suppress in onepart of its petals all vibrations we call red, in another thosewe call yellow, and purple, and reflect each of these in otherparts of the same tender petal. "Pansies are for thoughts, " evenmore thoughts than poor Ophelia knew. An evening cloud that isdense enough to absorb all the faster and weaker vibrations, leavingonly the stronger to come through, will be said to be red; becausethe vibrations that produce the impression we have so named arethe only ones that have vigor enough to get through. It is like anarmy charging upon a fortress. Under the deadly fire and fearfulobstructions six-sevenths go down, but one-seventh comes throughwith the glory of victory upon its face. Light comes in undulations to the eye, as tones of sound to theear. Must not light also sing? The lowest tone we can hear is madeby 16. 5 vibrations of air per second; the highest, so shrill and"fine that nothing lives 'twixt it and silence, " is made by 38, 000vibrations per second. Between these extremes lie eleven octaves;C of the G clef having 258-7/8 vibrations to the second, and itsoctave above 517-1/2. Not that sound vibrations cease [Page 27] at38, 000, but our organs are not fitted to hear beyond thoselimitations. If our ears were delicate enough, we could hear even upto the almost infinite vibrations of light. In one of thosesemi-inspirations we find in Shakspeare's works, he says-- "There's not the smallest orb which thou beholdest, But in his motion like an angel sings, Still quiring to the young-eyed cherubim. Such harmony is in immortal souls; But, whilst this muddy vesture of decay Doth grossly close it in, we cannot hear it. " And that older poetry which is always highest truth says, "Themorning stars sing together. " We misconstrued another passage whichwe could not understand, and did not dare translate as it was written, till science crept up to a perception of the truth that had beenstanding there for ages, waiting a mind that could take it in. Now we read as it is written--"Thou makest the out-goings of themorning and evening to sing. " Were our senses fine enough, we couldhear the separate keynote of every individual star. Stars differin glory and in power, and so in the volume and pitch of theirsong. Were our hearing sensitive enough, we could hear not onlythe separate key-notes but the infinite swelling harmony of thesemyriad stars of the sky, as they pour their mighty tide of unitedanthems in the ear of God: "In reason's ear they all rejoice, And utter forth a glorious voice. Forever singing, as they shine, The hand that made us is divine. " This music is not monotonous. Stars draw near each other, and makea light that is unapproachable by mortals; [Page 28] then the musicswells beyond our ability to endure. They recede far away, making alight so dim that the music dies away, so near to silence that onlyspirits can perceive it. No wonder God rejoices in his works. Theypour into his ear one ceaseless tide of rapturous song. Our senses are limited--we have only five, but there is room formany more. Some time we shall be taken out of "this muddy vestureof decay, " no longer see the universe through crevices of ourprison-house, but shall range through wider fields, explore deepermysteries, and discover new worlds, hints of which have never yetbeen blown across the wide Atlantic that rolls between them andmen abiding in the flesh. _Chemistry of Suns revealed by Light. _ When we examine the assemblage of colors spread from the white rayof sunlight, we do not find red simple red, yellow yellow, etc. , but there is a vast number of fine microscopic lines of variouslengths, parallel--here near together, there far apart, always thesame number and the same relative distance, when the same lightand prism are used. What new alphabets to new realms of knowledgeare these! Remember, that what we call colors are only variousnumbers of vibrations of ether. Remember, that every little group inthe infinite variety of these vibrations may be affected differentlyfrom every other group. One number of these is bent by the prismto where we see what we call the violet, another number to theplace we call red. All of the vibrations are destroyed when theystrike a surface we call black. A part of them are destroyed when[Page 29] they strike a substance we call colored. The rest arereflected, and give the impression of color. In one place on theflag of our nation all vibrations are destroyed except the red; inanother, all but the blue. Perhaps on that other gorgeous flag, notof our country but of our sun, the flag we call the solar spectrum, all vibrations are destroyed where these dark lines appear. Perhapsthis effect is not produced by the surface upon which the rays fall, but by some specific substance in the sun. This is just the truth. Light passing through vapor of sodium has the vibrations that wouldfall on two narrow lines in the yellow utterly destroyed, leavingtwo black spaces. Light passing through vapor of burning iron hassome four hundred numbers or kinds of vibrations destroyed, leavingthat number of black lines; but if the salt or iron be glowing gas, in the source of the light itself the same lines are bright insteadof dark. Thus we have brought to our doors a readable record of the verysubstances composing every world hot enough to shine by its ownlight. Thus, while our flag means all we have of liberty, free asthe winds that kiss it, and bright as the stars that shine in it, the flag of the sun means all that it is in constituent elements, all that it is in condition. We find in our sun many substances known to exist in the earth, and some that we had not discovered when the sun wrote their names, or rather made their mark, in the spectrum. Thus, also, we findthat Betelguese and Algol are without any perceivable indicationsof hydrogen, and Sirius has it in abundance. What a sense ofacquaintanceship it gives us to look up and recognize [Page 30] thestars whose very substance we know! If we were transported thither, or beyond, we should not be altogether strangers in an unknownrealm. But the stars differ in their constituent elements; every ray thatflashes from them bears in its very being proofs of what they are. Hence the eye of Omniscience, seeing a ray of light anywhere inthe universe, though gone from its source a thousand years, wouldbe able to tell from what orb it originally came. _Creative Force of Light. _ Just above the color vibrations of the unbraided sunbeam, abovethe violet, which is the highest number our eyes can detect, isa chemical force; it works the changes on the glass plate inphotography; it transfigures the dark, cold soil into woody fibre, green leaf, downy rose petals, luscious fruit, and far pervasiveodor; it flushes the wide acres of the prairie with grass and flowers, fills the valleys with trees, and covers the hills with corn, asingle blade of which all the power of man could not make. This power is also fit and able to survive. The engineer Stephensononce asked Dr. Buckland, "What is the power that drives that train?"pointing to one thundering by. "Well, I suppose it is one of yourbig engines. " "But what drives the engine?" "Oh, very likely a cannyNewcastle driver. " "No, sir, " said the engineer, "it is sunshine. "The doctor was too dull to take it in. Let us see if we can tracesuch an evident effect to that distant cause. Ages ago the warmsunshine, falling on the scarcely lifted hills of Pennsylvania, caused the reedy vegetation to grow along the banks of [Page 31]shallow seas, accumulated vast amounts of this vegetation, sunk itbeneath the sea, roofed it over with sand, compacted the sand intorock, and changed this vegetable matter--the products of thesunshine--into coal; and when it was ready, lifted it once more, allgarnered for the use of men, roofed over with mighty mountains. Wemine the coal, bring out the heat, raise the steam, drive the train, so that in the ultimate analyses it is sunshine that drives thetrain. These great beds of coal are nothing but condensedsunshine--the sun's great force, through ages gone, preserved forour use to-day. And it is so full of force that a piece of coal thatwill weigh three pounds (as big as a large pair of fists) has asmuch power in it as the average man puts into a day's work. Threetons of coal will pump as much water or shovel as much sand as theaverage man will pump or shovel in a lifetime; so that if a manproposes to do nothing but work with his muscles, he had better digthree tons of coal and set that to do his work and then die, becausehis work will be better done, and without any cost for themaintenance of the doer. Come down below the color vibrations, and we shall find that thosewhich are too infrequent to be visible, manifest as heat. Naturallythere will be as many different kinds of heat as tints of color, because there is as great a range of numbers of vibration. It isour privilege to sift them apart and sort them over, and find whatkinds are best adapted to our various uses. Take an electric lamp, giving a strong beam of light and heat, andwith a plano-convex lens gather it into a single beam and directit upon a thermometer, twenty feet away, that is made of glassand filled with air. The [Page 32] expansion or contraction of thisair will indicate the varying amounts of heat. Watch yourair-thermometer, on which the beam of heat is pouring, for theresult. There is none. And yet there is a strong current of heatthere. Put another kind of test of heat beyond it and it appears;coat the air-thermometer with a bit of black cloth, and that willabsorb heat and reveal it. But why not at first? Because the glasslens stops all the heat that can affect glass. The twenty feet ofair absorbs all the heat that affects air, and no kind of heat isleft to affect an instrument made of glass and air; but there arekinds of heat enough to affect instruments made of other things. A very strong current of heat may be sent right through the heartof a block of ice without melting the ice at all or cooling offthe heat in the least. It is done in this way: Send the beam ofheat through water in a glass trough, and this absorbs all the heatthat can affect water or ice, getting itself hot, and leaving allother kinds of heat to go through the ice beyond; and appropriatetests show that as much heat comes out on the other side as goesin on this side, and it does not melt the ice at all. Gunpowdermay be exploded by heat sent through ice. Dr. Kane, years ago, made this experiment. He was coming down from the north, and fellin with some Esquimaux, whom he was anxious to conciliate. He saidto the old wizard of the tribe, "I am a wizard; I can bring thesun down out of the heavens with a piece of ice. " That was a good, deal to say in a country where there was so little sun. "So, " hewrites, "I took my hatchet, chipped a small piece of ice into theform of a double-convex lens, [Page 33] smoothed it with my warmhands, held it up to the sun, and, as the old man was blind, Ikindly burned a blister on the back of his hand to show him I coulddo it. " These are simple illustrations of the various kinds of heat. Thebest furnace or stove ever invented consumes fifteen times as muchfuel to produce a given amount of heat as the furnace in our bodiesconsumes to produce a similar amount. We lay in our supplies ofcarbon at the breakfast, dinner, and supper table, and keep ourselveswarm by economically burning it with the oxygen we breathe. Heat associated with light has very different qualities from thatwhich is not. Sunlight melts ice in the middle, bottom, and top atonce. Ice in the spring-time is honey-combed throughout. A pieceof ice set in the summer sunshine crumbles into separate crystals. Dark heat only melts the surface. Nearly all the heat of the sun passes through glass without hinderance;but take heat from white-hot platinum and only seventy-six per cent. Of it goes through glass, twenty-four per cent. Being so constitutedthat it cannot pass with facility. Of heat from copper at 752°only six per cent. Can go through glass, the other ninety-four percent. Being absorbed by it. The heat of the sun beam goes through glass without [Page 34] anyhinderance whatever. It streams into the room as freely as if therewere no glass there. But what if the furnace or stove heat wentthrough glass with equal facility? We might as well try to heat ourrooms with the window-panes all out, and the blast of wintersweeping through them. The heat of the sun, by its intense vibrations, comes to the earthdowered with a power which pierces the miles of our atmosphere, but if our air were as pervious to the heat of the earth, thisheat would flyaway every night, and our temperature would go downto 200° below zero. This heat comes with the light, and then, dissociated from it, the number of its vibrations lessened, it isrobbed of its power to get away, and remains to work its beneficentends for our good. Worlds that are so distant as to receive only 1/1000 of the heatwe enjoy, may have atmospheres that retain it all. Indeed it isprobable that Mars, that receives but one-quarter as much heatas the earth, has a temperature as high as ours. The poet drew onhis imagination when he wrote: "Who there inhabit must have other powers, Juices, and veins, and sense and life than ours; One moment's cold like theirs would pierce the bone, Freeze the heart's-blood, and turn us all to stone. " The power that journeys along the celestial spaces in the flashingsunshine is beyond our comprehension. It accomplishes with easewhat man strives in vain to do with all his strength. At West Pointthere are some links of a chain that was stretched across the riverto prevent British ships from ascending; these links were madeof two-and-a-quarter-inch iron. A powerful locomotive might tugin vain at one of them and not stretch it the thousandth part ofan inch. But the heat of a single gas-burner, that glows with thepreserved sunlight of other ages, when suitably applied to thelink, stretches it with ease; such enormous power has a littleheat. There is a certain iron bridge across the Thames at London, resting on arches. The warm sunshine, acting [Page 35] upon theiron, stations its particles farther and farther apart. Since thebottom cannot give way the arches must rise in the middle. As theybecome longer they lift the whole bridge, and all the thunderinglocomotives and miles of goods-trains cannot bring that bridge downagain until the power of the sunshine has been withdrawn. There isBunker Hill Monument, thirty-two feet square at the base, with anelevation of two hundred and twenty feet. The sunshine of everysummer's day takes hold of that mighty pile of granite with itsaërial fingers, lengthens the side affected, and bends the wholegreat mass as easily as one would bend a whipstock. A few years agowe hung a plummet from the top of this monument to the bottom. At 9A. M. It began to move toward the west; at noon it swung round towardthe north; in the afternoon it went east of where it first was, andin the night it settled back to its original place. The sunshine says to the sea, held in the grasp of gravitation, "Rise from your bed! Let millions of tons of water fly on the wingsof the viewless air, hundreds of miles to the distant mountains, and pour there those millions of tons that shall refresh a wholecontinent, and shall gather in rivers fitted to bear the commerceand the navies of nations. " Gravitation says, "I will hold everyparticle of this ocean as near the centre of the earth as I can. "Sunshine speaks with its word of power, and says, "Up and away!"And in the wreathing mists of morning these myriads of tons risein the air, flyaway hundreds of miles, and supply all the Niagaras, Mississippis and Amazons of earth. The sun says to the earth, wrappedin the mantle of winter, [Page 36] "Bloom again;" and the snowsmelt, the ice retires, and vegetation breaks forth, birds sing, andspring is about us. Thus it is evident that every force is constitutionally arrangedto be overcome by a higher, and all by the highest. Gravitation ofearth naturally and legitimately yields to the power of the sun'sheat, and then the waters fly into the clouds. It as naturallyand legitimately yields to the power of mind, and the waters of theRed Sea are divided and stand "upright as an heap. " Water naturallybursts into flame when a bit of potassium is thrown into it, andas naturally when Elijah calls the right kind of fire from above. What seems a miracle, and in contravention of law, is only theconstitutional exercise of higher force over forces organized tobe swayed. If law were perfectly rigid, there could be but oneforce; but many grades exist from cohesion to mind and spirit. The highest forces are meant to have victory, and thus give thehighest order and perfectness. Across the astronomic spaces reach all these powers, making creationa perpetual process rather than a single act. It almost seems asif light, in its varied capacities, were the embodiment of God'screative power; as if, having said, "Let there be light, " he need donothing else, but allow it to carry forward the creative processesto the end of time. It was Newton, one of the earliest and mostacute investigators in this study of light, who said, "I seem tohave wandered on the shore of Truth's great ocean, and to havegathered a few pebbles more beautiful than common; but the vastocean itself rolls before me undiscovered and unexplored. " [Page 37]EXPERIMENTS WITH LIGHT. A light set in a room is seen from every place; hence light streamsin every possible direction. If put in the centre of a hollow sphere, every point of the surface will be equally illumined. If put ina sphere of twice the diameter, the same light will fall on allthe larger surface. The surfaces of spheres are as the squaresof their diameters; hence, in the larger sphere the surface isillumined only one-quarter as much as the smaller. The same is trueof large and small rooms. In Fig. 7 it is apparent that the lightthat falls on the first square is spread, at twice the distance, over the second square, which is four times as large, and at threetimes the distance over nine times the surface. The varying amountof light received by each planet is also shown in fractions aboveeach world, the amount received by the earth being 1. [Illustration: Fig. 7. ] [Illustration: Fig. 8. --Measuring Intensities of Light. ] The intensity of light is easily measured. Let two lights of differentbrightness, as in Fig. 8, cast shadows on the same screen. Arrangethem as to distance so that both shadows shall be equally dark. Let them fall side by side, and study them carefully. Measure therespective distances. Suppose one is twenty inches, the other forty. Light varies as the square [Page 38] of the distance: the square of20 is 400, of 40 is 1600. Divide 1600 by 400, and the result is thatone light is four times as bright as the other. [Illustration: Fig. 9. --Reflection and Diffusion of Light. ] Light can be handled, directed, and bent, as well as iron bars. Darken a room and admit a beam of sunlight through a shutter, ora ray of lamp-light through the key-hole. If there is dust in theroom it will be observed that light goes in straight lines. Becauseof this men are able to arrange houses and trees in rows, the hunteraims his rifle correctly, and the astronomer projects straightlines to infinity. Take a hand-mirror, or better, a piece of glasscoated on one side with black varnish, and you can send your rayanywhere. By using two mirrors, or having an assistant and usingseveral, you can cause a ray of light to turn as many corners as youplease. I once saw Mr. Tyndall send a ray into a glass jar filledwith smoke (Fig. 9). Admitting a slender ray through a small hole ina card over the mouth, one ray appeared; removing the cover, thewhole jar was luminous; as the smoke disappeared in spots cavitiesof darkness appeared. Turn the same ray into a tumbler of water, [Page 39]it becomes faintly visible; stir into it a teaspoonful of milk, thenturn in the ray of sunlight, and it glows like a lamp, illuminatingthe whole room. These experiments show how the straight rays ofthe sun are diffused in every direction over the earth. Set a small light near one edge of a mirror; then, by putting theeye near the opposite edge, you see almost as many flames as youplease from the multiplied reflections. How can this be accountedfor? Into your beam of sunlight, admitted through a half-inch hole, put the mirror at an oblique angle; you can arrange it so as tothrow half a dozen bright spots on the opposite wall. [Illustration: Fig. 10. --Manifold Reflections. ] In Fig. 10 the sunbeam enters at A, and, striking the mirror _m_at _a_, is partly reflected to 1 on the wall, and partly entersthe glass, passes through to the silvered back at B, and is totallyreflected to _b_, where it again divides, some of it going to thewall at 2, and the rest, continuing to make the same reflectionsand divisions, causes spots 3, 4, 5, etc. The brightest spot isat No. 2, because the silvered glass at B is the best reflectorand has the most light. When the discovery of the moons of Mars was announced in 1877, it was also widely published that they could be seen by a mirror. Of course this is impossible. The point of light mistaken for themoon in this secondary reflection was caused by holding the mirrorin an oblique position. Take a small piece of mirror, say an inch in surface, and puttingunder it three little pellets of wax, putty, or clay, set it onthe wrist, with one of the pellets on the pulse. Hold the mirrorsteadily in the beam of light, and the frequency and prominence ofeach pulse-beat will be indicated by the tossing spot of light onthe wall. If the operator becomes excited the fact will be evidentto all observers. [Illustration: Fig. 11. ] Place a coin in a basin (Fig. 11), and set it so that the rim willconceal the coin from the eye. Pour in water, and the coin will[Page 40] appear to rise into sight. When light passes from a mediumof one density to a medium of another, its direction is changed. Thus a stick in water seems bent. Ships below the horizon aresometimes seen above, because of the different density of the layersof air. Thus light coming from the interstellar spaces, and entering ouratmosphere, is bent down more and more by its increasing density. The effect is greatest when the sun or star is near the horizon, none at all in the zenith. This brings the object into view beforeit is risen. Allowance for this displacement is made in all delicateastronomical observations. [Illustration: Fig. 12. --Atmospherical Refraction. ] Notice on the floor the shadow of the window-frames. The glassof almost every window is so bent as to turn the sunlight asideenough to obliterate some of the shadows or increase their thickness. DECOMPOSITION OF LIGHT. Admit the sunbeam through a slit one inch long and one-twentiethof an inch wide. Pass it through a prism. Either purchase one ormake it of three plain pieces of glass one and a half inch wideby six inches long, fastened together in triangular shape--fastenthe edges with hot wax and fill it with water; then on a screenor wall you will have the colors of the rainbow, not merely sevenbut seventy, if your eyes are sharp enough. Take a bit of red paper that matches the red color of the spectrum. Move it along the line of colors toward the violet. In the orangeit is dark, in the yellow darker, in the green and all beyond, black. That is because there are no more red rays to be reflectedby it. So a green object is true to its color only in the greenrays, and black elsewhere. All these colors may be recombined bya second prism into white light. [Page 41]III. ASTRONOMICAL INSTRUMENTS. "The eyes of the Lord are in every place. "--_Proverbs_ xv. 3. [Page 42]"Man, having one kind of an eye given him by his Maker, proceedsto construct two other kinds. He makes one that magnifies invisibleobjects thousands of times, so that a dull razor-edge appears asthick as three fingers, until the amazing beauty of color and formin infinitesimal objects is entrancingly apparent, and he knows thatGod's care of least things is infinite. Then he makes the other kindfour or six feet in diameter, and penetrates the immensities of spacethousands of times beyond where his natural eye can pierce, until hesees that God's immensities of worlds are infinite also. "--BISHOPFOSTER. [Page 43]III. _THE TELESCOPE. _ Frequent allusion has been made in the previous chapter to discoveredresults. It is necessary to understand more clearly the process bywhich such results have been obtained. Some astronomical instrumentsare of the simplest character, some most delicate and complex. When a man smokes a piece of glass, in order to see an eclipseof the sun, he makes a simple instrument. Ferguson, lying on hisback and slipping beads on a string at a certain distance abovehis eye, measured the relative distances of the stars. The useof more complex instruments commenced when Galileo applied thetelescope to the heavens. He cannot be said to have invented thetelescope, but he certainly constructed his own without a pattern, and used it to good purpose. It consists of a lens, O B (Fig. 13), which acts as a multiple prism to bend all the rays to one pointat R. Place the eye there, and it receives as much light as if itwere as large as the lens O B. The rays, however, are convergent, and the point difficult to [Page 44] find. Hence there is placed atR a concave lens, passing through which the rays emerge in parallellines, and are received by the eye. Opera-glasses are made uponprecisely this principle to-day, because they can be madeconveniently short. [Illustration: Fig. 13. --Refracting Telescope. ] If, instead of a concave lens at R, converting the converging raysinto parallel ones, we place a convex or magnifying lens, the minuteimage is enlarged as much as an object seems diminished when thetelescope is reversed. This is the grand principle of the refractingtelescope. Difficulties innumerable arise as we attempt to enlargethe instruments. These have been overcome, one after another, untilit is now felt that the best modern telescope, with an object lensof twenty-six inches, has fully reached the limit of optical power. _The Reflecting Telescope_. This is the only kind of instrument differing radically from therefracting one already described. It receives the light in a concavemirror, M (Fig. 14), which reflects it to the focus F, producing thesame result as the lens of the refracting telescope. Here a mirrormay be placed obliquely, reflecting the image at right angles to theeye, outside the tube, in which case it is called the Newtoniantelescope; or a mirror at R may be placed perpendicularly, and sendthe rays through [Page 45] an opening in the mirror at M. This formis called the Gregorian telescope. Or the mirror M may be slightlyinclined to the coming rays, so as to bring the point F entirelyoutside the tube, in which case it is called the Herscheliantelescope. In either case the image may be magnified, as in therefracting telescope. [Illustration: Fig. 14. --Reflecting Telescope. ] Reflecting telescopes are made of all sizes, up to the Cyclopeaneye of the one constructed by Lord Rosse, which is six feet indiameter. The form of instrument to be preferred depends on theuse to which it is to be put. The loss of light in passing throughglass lenses is about two-tenths. The loss by reflection is oftenone-half. In view of this peculiarity and many others, it is heldthat a twenty-six-inch refractor is fully equal to any six-footreflector. The mounting of large telescopes demands the highest engineeringability. The whole instrument, with its vast weight of a twenty-six-inchglass lens, with its accompanying tube and appurtenances, must bepointed as nicely as a rifle, and held as steadily as the axisof the globe. To give it the required steadiness, the foundationon which it is placed is sunk deep in the earth, far from rail orother roads, and no part of the observatory is allowed to touchthis support. When a star is once found, the earth swiftly rotatesthe telescope away from it, and it passes out of the field. Toavoid this, clock-work is so arranged that the great telescopefollows the star by the hour, if required. It will take a star atits eastern rising, and hold it constantly in view while it climbsto the meridian and sinks in the west (Fig. 15). The reflectordemands still more difficult engineering. That of Lord Rosse hasa metallic mirror [Page 46] weighing six tons, a tube forty feetlong, which, with its appurtenances, weighs seven tons more. Itmoves between two walls only 10° east and west. The new Parisreflector (Fig. 16) has a much wider range of movement. [Illustration: Fig. 15. --Cambridge Equatorial. ] [Illustration: Fig. 16. --New Paris Reflector. ] _The Spectroscope. _ A spectrum is a collection of the colors which are dispersed bya prism from any given light. If it is sunlight, it is a solarspectrum; if the source of light is a [Page 49] star, candle, glowing metal, or gas, it is the spectrum of a star, candle, glowingmetal, or gas. An instrument to see these spectra is called aspectroscope. Considering the infinite variety of light, and itseasy modification and absorption, we should expect an immense numberof spectra. A mere prism disperses the light so imperfectly thatdifferent orders of vibrations, perceived as colors, are mingled. Noeye can tell where one commences or ends. Such a spectrum is said tobe impure. What we want is that each point in the spectrum should bemade of rays of the same number of vibrations. As we can let only asmall beam of light pass through the prism, in studying celestialobjects with a telescope and spectroscope we must, in everyinstance, contract the aperture of the instrument until we get onlya small beam of light. In order to have the colors thoroughlydispersed, the best instruments pass the beam of light through aseries of prisms called a battery, each one spreading farther thecolors which the previous ones had spread. In Fig. 17 the ray isseen entering through the telescope A, which renders the raysparallel, and passing [Page 50] through the prisms out to telescopeB, where the spectrum can be examined on the retina of the eye for ascreen. In order to still farther disperse the rays, some batteriesreceive the ray from the last prism at O upon an oblique mirror, send it up a little to another, which delivers it again to the prismto make its journey back again through them all, and come out to beexamined just above where it entered the first prism. [Illustration: Fig. 17. --Spectroscope, with Battery of Prisms. ] Attached to the examining telescope is a diamond-ruled scale of glass, enabling us to fix the position of any line with great exactness. [Illustration: Fig. 18. --Spectra of glowing Hydrogen and the Sun. ] In Fig. 18 is seen, in the lower part, a spectrum of the sun, withabout a score of its thousands of lines made evident. In the upperpart is seen the spectrum of bright lines given by glowing hydrogengas. These lines are given by no other known gas; they are itsautograph. It is readily observed that they precisely correspondwith certain dark lines in the solar spectrum. Hence we easilyknow that a glowing gas gives the same bright lines that it absorbsfrom the light of another source passing through it--that is, glowinggas gives out the same rays of light that it absorbs when it isnot glowing. The subject becomes clearer by a study of the chromolithic plate. No. 1 represents the solar spectrum, with a few of its lines on anaccurately graduated scale. [Page 51] No. 3 shows the bright line ofglowing sodium, and, corresponding to a dark line in the solarspectrum, shows the presence of salt in that body. No. 2 shows thatpotassium has some violet rays, but not all; and there being no darkline to correspond in the solar spectrum, we infer its absence fromthe sun. No. 6 shows the numerous lines and bands of barium--severalred, orange, yellow, and four are very bright green ones. The linesgiven by any volatilized substances are always in the same place onthe scale. A patient study of these signs of substances reveals, richer resultsthan a study of the cuniform characters engraved on Assyrian slabs;for one is the handwriting of men, the other the handwriting ofGod. One of the most difficult and delicate problems solved by thespectroscope is the approach or departure of a light-giving bodyin the line of sight. Stand before a locomotive a mile away, youcannot tell whether it approaches or recedes, yet it will dash byin a minute. How can the movements of the stars be comprehendedwhen they are at such an immeasurable distance? It can best be illustrated by music. The note C of the G clef ismade by two hundred and fifty-seven vibrations of air per second. Twice as many vibrations per second would give us the note C an octaveabove. Sound travels at the rate of three hundred and sixty-fouryards per second. If the source of these two hundred and fifty-sevenvibrations could approach us at three hundred and sixty-four yardsper second, it is obvious that twice as many waves would be putinto a given space, and we should hear the upper C when only wavesenough were made for the lower C. The same [Page 52] result wouldappear if we carried our ear toward the sound fast enough to take uptwice as many valves as though we stood still. This is apparent toevery observer in a railway train. The whistle of an approachinglocomotive gives one tone; it passes, and we instantly detectanother. Let two trains, running at a speed of thirty-six yards asecond, approach each other. Let the whistle of one sound the noteE, three hundred and twenty-three vibrations per second. It will beheard on the other as the note G, three hundred and eighty-eightvibrations per second; for the speed of each train crowds thevibrations into one-tenth less room, adding 32+ vibrations persecond, making three hundred and eighty-eight in all. The trainspass. The vibrations are put into one-tenth more space by thewhistle making them, and the other train allows only nine-tenths ofwhat there are to overtake the ear. Each subtracts 32+ vibrationsfrom three hundred and twenty-three, leaving only two hundred andfifty-eight, which is the note C. Yet the note E was constantlyuttered. [Illustration: 1. Solar Spectrum. 2. Spectrum of Potassium. 3. Spectrum of Sodium. 4. Spectrum of Strontium. 5. Spectrum of Calcium. 6. Spectrum of Barium. ] If a source of light approach or depart, it will have a similareffect on the light waves. How shall we detect it? If a star approachus, it puts a greater number of waves into an inch, and shortens theirlength. If it recedes, it increases the length of the wave--putsa less number into an inch. If a body giving only the number ofvibrations we call green were to approach sufficiently fast, itwould crowd in vibrations enough to appear what we call blue, indigo, or even violet, according to its speed. If it receded sufficientlyfast, it would leave behind it only vibrations enough to fill up[Page 53] the space with what we call yellow, orange, or red, according to its speed; yet it would be green, and green only, allthe time. But how detect the change? If red waves are shortened theybecome orange in color; and from below the red other rays, too farapart to be seen by the eye, being shortened, become visible as red, and we cannot know that anything has taken place. So, if a starrecedes fast enough, violet vibrations being lengthened becomeindigo; and from above the violet other rays, too short to be seen, become lengthened into visible violet, and we can detect no movementof the colors. The dark lines of the spectrum are the cutting out ofrays of definite wave-lengths. If the color spectrum moves away, they move with it, and away from their proper place in the ordinaryspectrum. If, then, we find them toward the red end, the star isreceding; if toward the violet end, it is approaching. Turn theinstrument on the centre of the sun. The dark lines take theirappropriate place, and are recognized on the ruled scale. Turn it onone edge, that is approaching us one and a quarter miles a second bythe revolution of the sun on its axis, the spectral lines movetoward the violet end; turn the spectroscope toward the other edgeof the sun, it is receding from us one and a quarter miles a secondby reason of the axial revolution, and the spectral lines movetoward the red end. Turn it near the spots, and it reveals themighty up-rush in one place and the down-rush in another of onehundred miles a second. We speak of it as an easy matter, but it isa problem of the greatest delicacy, almost defying the mind of manto read the movements of matter. It should be recognized that Professor Young, of [Page 54]Princeton, is the most successful operator in this recent realm ofscience. He already proposes to correct the former estimate of thesun's axial revolutions, derived from observing its spots, by thesurer process of observing accelerated and retarded light. Within a very few years this wonderful instrument, the spectroscope, has made amazing discoveries. In chemistry it reveals substancesnever known before; in analysis it is delicate to the detection ofthe millionth of a grain. It is the most deft handmaid of chemistry, the arts, of medical science, and astronomy. It tells the chemicalconstitution of the sun, the movements taking place, the nature ofcomets, and nebulæ. By the spectroscope we know that the atmospheresof Venus and Mars are like our own; that those of Jupiter and Saturnare very unlike; it tells us which stars approach and which recede, and just how one star differeth from another in glory and substance. In the near future we shall have the brilliant and diversely coloredflowers of the sky as well classified into orders and species asare the flowers of the earth. [Page 55]IV. CELESTIAL MEASUREMENTS. "Who hath measured the waters in the hollow of his hand, and metedout heaven with the span? Mine hand also hath laid the foundationof the earth, and my right hand hath spanned the heavens. "--_Isa. _xl. 12; xlviii. 13. [Page 56] "Go to yon tower, where busy science plies Her vast antennæ, feeling thro' the skies; That little vernier, on whose slender lines The midnight taper trembles as it shines, A silent index, tracks the planets' march In all their wanderings thro' the ethereal arch, Tells through the mist where dazzled Mercury burns, And marks the spot where Uranus returns. "So, till by wrong or negligence effaced, The living index which thy Maker traced Repeats the line each starry virtue draws Through the wide circuit of creation's laws; Still tracks unchanged the everlasting ray Where the dark shadows of temptation stray; But, once defaced, forgets the orbs of light, And leaves thee wandering o'er the expanse of night. " OLIVER WENDELL HOLMES. [Page 57]IV. _CELESTIAL MEASUREMENTS. _ We know that astronomy has what are called practical uses. If aship had been driven by Euroclydon ten times fourteen days andnights without sun or star appearing, a moment's glance into theheavens from the heaving deck, by a very slightly educated sailor, would tell within one hundred yards where he was, and determinethe distance and way to the nearest port. We know that, in allfinal and exact surveying, positions must be fixed by the stars. Earth's landmarks are uncertain and easily removed; those whichwe get from the heavens are stable and exact. In 1878 the United States steam-ship _Enterprise_ was sent to surveythe Amazon. Every night a "star party" went ashore to fix the exactlatitude and longitude by observations of the stars. Our real landmarksare not the pillars we rear, but the stars millions of miles away. All our standards of time are taken from the stars; every railwaytrain runs by their time to avoid collision; by them all factoriesstart and stop. Indeed, we are ruled by the stars even more thanthe old astrologers imagined. Man's finest mechanism, highest thought, and broadest exerciseof the creative faculty have been inspired by astronomy. No otherinstruments approximate in delicacy those which explore the heavens;no other [Page 58] system of thought can draw such vast and certainconclusions from its premises. "Too low they build who build beneaththe stars;" we should lay our foundations in the skies, and thenbuild upward. We have been placed on the outside of this earth, instead of theinside, in order that we may look abroad. We are carried about, through unappreciable distance, at the inconceivable velocity ofone thousand miles a minute, to give us different points of vision. The earth, on its softly-spinning axle, never jars enough to unnesta bird or wake a child; hence the foundations of our observatoriesare firm, and our measurements exact. Whoever studies astronomy, under proper guidance and in the right spirit, grows in thoughtand feeling, and becomes more appreciative of the Creator. _Celestial Movements. _ Let it not be supposed that a mastery of mathematics and a finishededucation are necessary to understand the results of astronomicalresearch. It took at first the highest power of mind to make thediscoveries that are now laid at the feet of the lowliest. It tooksublime faith, courage, and the results of ages of experience innavigation, to enable Columbus to discover that path to the NewWorld which now any little boat can follow. Ages of experienceand genius are stored up in a locomotive, but quite an unletteredman can drive it. It is the work of genius to render difficultmatters plain, abstruse thoughts clear. [Illustration: Fig. 19. ] A brief explanation of a few terms will make the principles ofworld inspection easily understood. Imagine a perfect circle thirtyfeet in diameter--that is, create [Page 59] one (Fig. 19). Drawthrough it a diameter horizontally, another perpendicularly. Theangles made by the intersecting lines are each said to be ninetydegrees, marked thus °. The arc of a circle included between any twoof the lines is also 90°. Every circle, great or small, is dividedinto these 360°. If the sun rose in the east and came to the zenithat noon, it would have passed 90°. When it set in the west it wouldhave traversed half the circle, or 180°. In Fig. 20 the angle of thelines measured on the graduated arc is 10°. The mountain is 10°high, the world 10° in diameter, the comet moves 10° a day, thestars are 10° apart. The height of the mountain, the diameter of theworld, the velocity of the comet, and the distance between thestars, depend on the distance of each from the point of sight. Everydegree is divided into 60 minutes (marked '), and every minute into60 seconds (marked "). [Illustration: Fig. 20. --Illustration of Angles. ] Imagine yourself inside a perfect sphere one hundred feet in diameter, with the interior surface above, around, and below studded withfixed bright points like stars. The familiar constellations ofnight might be blazoned there in due proportion. If this star-sprent sphere were made to revolve once in twenty-fourhours, all the stars would successively [Page 60] pass in review. How easily we could measure distances between stars, from a certainfixed meridian, or the equator! How easily we could tell when anyparticular star would culminate! It is as easy to take all thesemeasurements when our earthly observatory is steadily revolvedwithin the sphere of circumambient stars. Stars can be mapped asreadily as the streets of a great city. Looking down on it in thenight, one could trace the lines of lighted streets, and judgesomething of its extent and regularity. But the few lamps of eveningwould suggest little of the greatness of the public buildings, themagnificent enterprise and commerce of its citizens, or theintelligence of its scholars. Looking up to the lamps of thecelestial city, one can judge something of its extent andregularity; but they suggest little of the magnificence of the manymansions. Stars are reckoned as so many degrees, minutes, and seconds fromeach other, from the zenith, or from a given meridian, or from theequator. Thus the stars called the Pointers, in the Great Bear, are 5° apart; the nearest one is 29° from the Pole Star, which is39° 56' 29" above the horizon at Philadelphia. In going to Englandyou creep up toward the north end of the earth, till the Pole Staris 54° high. It stays near its place among the stars continually, "Of whose true-fixed and resting quality There is no fellow in the firmament. " _How to Measure. _ Suppose a telescope, fixed to a mural circle, to revolve on an axis, as in Fig. 21; point it horizontally at a star; [Page 61] turn it upperpendicular to another star. Of course the two stars are 90°apart, and the graduated scale, which is attached to the outer edgeof the circle, shows a revolution of a quarter circle, or 90°, But aperfect accuracy of measurement must be sought; for to mistake thebreadth of a hair, seen at the distance of one hundred andtwenty-five feet, would cause an error of 3, 000, 000 miles at thedistance of the sun, and immensely more at the distance of thestars. The correction of an inaccuracy of no greater magnitude thanthat has reduced our estimate of the distance of our sun 3, 000, 000miles. [Illustration: Fig. 21. --Mural Circle. ] Consider the nicety of the work. Suppose the graduated scale tobe thirty feet in circumference. Divided into 360°, each wouldbe one inch long. Divide each degree into 60', each one is 1/60of an inch long. It takes good eyesight to discern it. But eachminute must be [Page 62] divided into 60", and these must not onlybe noted, but even tenths and hundredths of seconds must bediscerned. Of course they are not seen by the naked eye; somemechanical contrivance must be called in to assist. A watch losestwo minutes a week, and hence is unreliable. It is taken to awatch-maker that every single second may be quickened 1/20160 partof itself. Now 1/20000 part of a second would be a small interval oftime to measure, but it must be under control. If the temperature ofa summer morning rises ten or twenty degrees we scarcely notice it;but the magnetic tastimeter measures 1/5000 of a degree. Come to earthly matters. In 1874, after nearly twenty-eight years'work, the State of Massachusetts opened a tunnel nearly five mileslong through the Hoosac Mountains. In the early part of the workthe engineers sunk a shaft near the middle 1028 feet deep. Then thequestion to be settled was where to go so as to meet the approachingexcavations from the east and west. A compass could not be reliedon under a mountain. The line must be mechanically fixed. A littledivergence at the starting-point would become so great, miles away, that the excavations might pass each other without meeting; thegrade must also rise toward the central shaft, and fall in workingaway from it; but the lines were fixed with such infinitesimalaccuracy that, when the one going west from the eastern portal andthe one going east from the shaft met in the heart of the mountain, the western line was only one-eighth of an inch too high, andthree-sixteenths of an inch too far north. To reach this perfectresult they had to triangulate from the eastern portal to distant[Page 63] mountain peaks, and thence down the valley to the centralshaft, and thus fix the direction of the proposed line across themouth of the shaft. Plumb-lines were then dropped one thousand andtwenty-eight feet, and thus the line at the bottom was fixed. Three attempts were made--in 1867, 1870, and 1872--to fix the exacttime-distance between Greenwich and Washington. These three separateefforts do not differ one-tenth of a second. Such demonstrable resultson earth greatly increase our confidence in similar measurementsin the skies. [Illustration: Fig. 22. ] A scale is frequently affixed to a pocket-rule, by which we caneasily measure one-hundredth of an inch (Fig. 22). The upper andlower line is divided into tenths of an inch. Observe the slantingline at the right hand. It leans from the perpendicular one-tenthof an inch, as shown by noticing where it reaches the top line. Whenit reaches the second horizontal line it has left the perpendicularone-tenth of that tenth--that is, one-hundredth. The intersectionmarks 99/100 of an inch from one end, and one-hundredth from theother. When division-lines, on measures of great nicety, get too fineto be read by the eye, we use the microscope. By its means we areable to count 112, 000 lines ruled on a glass plate within an inch. The smallest object that can be seen by a keen eye makes an angleof 40", but by putting six microscopes on the scale of the telescopeon the mural circle, we are able to reach an exactness of 0". 1, or1/3600 of an inch. This instrument is used to measure the declinationof stars, or angular [Page 64] distance north or south of theequator. Thus a star's place in two directions is exactly fixed. When the telescope is mounted on two pillars instead of the face ofa wall, it is called a transit instrument. This is used to determinethe time of transit of a star over the meridian, and if the transitinstrument is provided with a graduated circle it can also be usedfor the same purposes as the mural circle. Man's capacity to measureexactly is indicated in his ascertainment of the length of waves oflight. It is easy to measure the three hundred feet distance betweenthe crests of storm-waves in the wide Atlantic; easy to measure thedifferent wave-lengths of the different tones of musical sounds. Somen measure the lengths of the undulations of light. The shortest isof the violet light, 154. 84 ten-millionths of an inch. By thehorizontal pendulum Professor Root has made 1/36000000 of an inchapparent. The next elements of accuracy must be perfect time and perfectnotation of time. As has been said, we get our time from the stars. Thus the infinite and heavenly dominates the finite and earthly. Clocks are set to the invariable sidereal time. Sidereal noon iswhen we have turned ourselves under the point where the sun crossesthe equator in March, called the vernal equinox. Sidereal clocksare figured to indicate twenty-four hours in a day: they tick exactseconds. To map stars we wish to know the exact second when theycross the meridian, or the north and south line in the celestialdome above us. The telescope (Fig. 21, p. 61) swings exactly northand south. In its focus a set of fine threads of spider-lines isplaced (Fig. 23). The telescope is set just high enough, so thatby the rolling over of the earth [Page 65] the star will come intothe field just above the horizontal thread. The observer notes theexact second and tenth of a second when the star reaches eachvertical thread in the instrument, adds together the times anddivides by five to get the average, and the exact time is reached. [Illustration: Fig. 23. --Transit of a Star noted. ] But man is not reliable enough to observe and record with sufficientaccuracy. Some, in their excitement, anticipate its positive passage, and some cannot get their slow mental machinery in motion tillafter it has made the transit. Moreover, men fall into a habit ofestimating some numbers of tenths of a second oftener than others. It will be found that a given observer will say three tenths orseven tenths oftener than four or eight. He is falling into ruts, and not trustworthy. General O. M. Mitchel, who had been directorof the Cincinnati Observatory, once told one of his staff-officersthat he was late at an appointment. "Only a few minutes, " said theofficer, apologetically. "Sir, " said the general, "where I havebeen accustomed to work, hundredths of a second are too importantto be neglected. " And it is to the rare genius of this astronomer, and to others, that we owe the mechanical accuracy that we nowattain. The clock is made to mark its seconds on paper wrappedaround a revolving cylinder. Under the observer's fingers is anelectric key. This he can touch at the instant of the transit ofthe star [Page 66] over each wire, and thus put his observation onthe same line between the seconds dotted by the clock. Of coursethese distances can be measured to minute fractional parts of asecond. But it has been found that it takes an appreciable time for everyobserver to get a thing into his head and out of his finger-ends, and it takes some observers longer than others. A dozen men, seeingan electric spark, are liable to bring down their recording marksin a dozen different places on the revolving paper. Hence the timethat it takes for each man to get a thing into his head and outof his fingers is ascertained. This time is called his personalequation, and is subtracted from all of his observations in order toget at the true time; so willing are men to be exact about materialmatters. Can it be thought that moral and spiritual matters haveno precision? Thus distances east or west from any given star ormeridian are secured; those north and south from the equator orthe zenith are as easily fixed, and thus we make such accuratemaps of the heavens that any movements in the far-off stars--sofar that it may take centuries to render the swiftest movementsappreciable--may at length be recognized and accounted for. [Illustration: Fig. 24. ] We now come to a little study of the modes of measuring distances. Create a perfect square (Fig. 24); draw a diagonal line. The squareangles are 90°, the divided angles give two of 45° each. Now thebase A B is equal to the perpendicular A C. Now any point--C, wherea perpendicular, A C, and a diagonal, B C, meet--will be [Page 67]as far from A as B is. It makes no difference if a river flowsbetween A and C, and we cannot go over it; we can measure itsdistance as easily as if we could. Set a table four feet by eightout-doors (Fig. 25); so arrange it that, looking along one end, theline of sight just strikes a tree the other side of the river. Go tothe other end, and, looking toward the tree, you find the line ofsight to the tree falls an inch from the end of the table on thefarther side. The lines, therefore, approach each other one inch inevery four feet, and will come together at a tree three hundred andeighty-four feet away. [Illustration: Fig. 25. --Measuring Distances. ] [Illustration: Fig. 26. --Measuring Elevations. ] The next process is to measure the height or magnitude of objectsat an ascertained distance. Put two pins in a stick half an inchapart (Fig. 26). Hold it up two feet from the eye, and let theupper pin fall in line with your eye and the top of a distant churchsteeple, and the lower pin in line with the bottom of the church andyour eye. If the church is three-fourths of a mile away, it mustbe eighty-two feet high; if a mile away, it must be one hundredand ten feet high. For if two lines spread [Page 68] one-half aninch going two feet, in going four feet they will spread an inch, and in going a mile, or five thousand two hundred and eighty feet, they will spread out one-fourth as many inches, viz. , thirteenhundred and twenty--that is, one hundred and ten feet. Of coursethese are not exact methods of measurement, and would not be correctto a hair at one hundred and twenty-five feet, but they perfectlyillustrate the true methods of measurement. Imagine a base line ten inches long. At each end erect a perpendicularline. If they are carried to infinity they will never meet: willbe forever ten inches apart. But at the distance of a foot fromthe base line incline one line toward the other 63/10000000 ofan inch, and the lines will come together at a distance of threehundred miles. That new angle differs from the former right anglealmost infinitesimally, but it may be measured. Its value is aboutthree-tenths of a second. If we lengthen the base line from teninches to all the miles we can command, of course the point ofmeeting will be proportionally more distant. The angle made bythe lines where they come together will be obviously the same asthe angle of divergence from a right angle at this end. That angleis called the parallax of any body, and is the angle that wouldbe made by two lines coming from that body to the two ends of anyconventional base, as the semi-diameter of the earth. That thatangle would vary according to the various distances is easily seenby Fig. 27. [Illustration: Fig. 27. ] Let O P be the base. This would subtend a greater angle seen fromstar A than from star B. Let B be far enough away, and O P wouldbecome invisible, and B [Page 69] would have no parallax for thatbase. Thus the moon has a parallax of 57" with the semi-equatorialdiameter of the earth for a base. And the sun has a parallax 8". 85on the same base. It is not necessary to confine ourselves to rightangles in these measurements, for the same principles hold true inany angles. Now, suppose two observers on the equator should look atthe moon at the same instant. One is on the top of Cotopaxi, on thewest coast of South America, and one on the west coast of Africa. They are 90° apart--half the earth's diameter between them. The oneon Cotopaxi sees it exactly overhead, at an angle of 90° with theearth's diameter. The one on the coast of Africa sees its angle withthe same line to be 89° 59' 3"--that is, its parallax is 57". Trythe same experiment on the sun farther away, as is seen in Fig. 27, and its smaller parallax is found to be only 8". 85. It is not necessary for two observers to actually station themselvesat two distant parts of the earth in order to determine a parallax. If an observer could go from one end of the base-line to the other, he could determine both angles. Every observer is actually carriedalong through space by two motions: one is that of the earth'srevolution of one thousand miles an hour around the axis; and theother is the movement of the earth around the sun of one thousandmiles in a minute. Hence we can have the diameter not only of [Page70] the earth (eight thousand miles) for a base-line, but thediameter of the earth's orbit (184, 000, 000 miles), or any part ofit, for such a base. Two observers at the ends of the earth'sdiameter, looking at a star at the same instant, would find that itmade the same angle at both ends; it has no parallax on so short abase. We must seek a longer one. Observe a certain star on the 21stof March; then let us traverse the realms of space for six months, at one thousand miles a minute. We come round in our orbit to apoint opposite where we were six months ago, with 184, 000, 000 ofmiles between the points. Now, with this for a base-line, measurethe angles of the same stars: it is the same angle. Sitting in mystudy here, I glance out of the window and discern separate bricks, in houses five hundred feet away, with my unaided eye; they subtenda discernible angle. But one thousand feet away I cannot distinguishindividual bricks; their width, being only two inches, does notsubtend an angle apprehensible to my vision. So at these distantstars the earth's enormous orbit, if lying like a blazing ring inspace, with the world set on its edge like a pearl, and the sunblazing like a diamond in the centre, would all shrink to a merepoint. Not quite to a point from the nearest stars, or we shouldnever be able to measure the distance of any of them. Professor Airysays that our orbit, seen from the nearest star, would be the sameas a circle six-tenths of an inch in diameter seen at the distanceof a mile: it would all be hidden by a thread one-twenty-fifth of aninch in diameter, held six hundred and fifty feet from the eye. If astraight line could be drawn from a star, Sirius in the east to thestar Vega in the west, touching our [Page 71] earth's orbit on oneside, as T R A (Fig. 28), and a line were to be drawn six monthslater from the same stars, touching our earth's orbit on the otherside, as R B T, such a line would not diverge sufficiently from astraight line for us to detect its divergence. Numerous vainattempts had been made, up to the year 1835, to detect and measurethe angle of parallax by which we could rescue some one or more ofthe stars from the inconceivable depths of space, and ascertaintheir distance from us. We are ever impelled to triumph over what isdeclared to be unconquerable. There are peaks in the Alps no man hasever climbed. They are assaulted every year by men zealous of moreworlds to conquer. So these greater heights of the heavens have beenassaulted, till some ambitious spirits have outsoared evenimagination by the certainties of mathematics. [Illustration: Fig. 28. ] It is obvious that if one star were three times as far from us asanother, the nearer one would seem to be displaced by our movementin our orbit three times as much as the other; so, by comparing onestar with another, we reach a ground of judgment. The ascertainmentof longitude at sea by means of the moon affords a good illustration. Along the track where the moon sails, nine bright stars, four planets, and the sun have been selected. The nautical almanacs give thedistance of the moon from these successive stars every hour inthe night for three years in advance. The sailor can measure thedistance at any time by his sextant. Looking from the world atD (Fig. 29), the distance of the moon and [Page 72] star is A E, which is given in the almanac. Looking from C, the distance is onlyB E, which enables even the uneducated sailor to find the distance, C D, on the earth, or his distance from Greenwich. [Illustration: Fig. 29. --Mode of Ascertaining Longitude. ] So, by comparisons of the near and far stars, the approximate distanceof a few of them has been determined. The nearest one is the brighteststar in the Centaur, never visible in our northern latitudes, whichhas a parallax of about one second. The next nearest is No. 61 inthe Swan, or 61 Cygni, having a parallax of 0". 34. Approximatemeasurements have been made on Sirius, Capella, the Pole Star, etc. , about eighteen in all. The distances are immense: only theswiftest agents can traverse them. If our earth were suddenly todissolve its allegiance to the king of day, and attempt a flightto the North Star, and should maintain its flight of one thousandmiles a minute, it would flyaway toward Polaris for thousands uponthousands of years, till a million years had passed away, beforeit reached that northern dome of the distant sky, and gave itsnew allegiance to another sun. The sun it had left behind it wouldgradually diminish till it was small as Arcturus, then small ascould be discerned by the naked eye, until at last it would finallyfade out in utter darkness long before the new sun was reached. Light can traverse the distance around our earth eight times inone second. It comes in eight minutes from the sun, but it takesthree and a quarter years to come from Alpha [Page 73] Centauri, seven and a quarter years from 61 Cygni, and forty-five years fromthe Polar Star. Sometimes it happens that men steer along a lee shore, dependentfor direction on Polaris, that light-house in the sky. Sometimes ithas happened that men have traversed great swamps by night when thatstar was the light-housse of freedom. In either case the exigencyof life and liberty was provided for forty-five years before by aProvidence that is divine. We do not attempt to name in miles these enormous distances; wemust seek another yard-stick. Our astronomical unit and standard ofmeasurement is the distance of the earth from the sun--92, 500, 000miles. This is the golden reed with which we measure the celestialcity. Thus, by laying down our astronomical unit 226, 000 times, wemeasure to Alpha Centauri, more than twenty millions of millionsof miles. Doubtless other suns are as far from Alpha Centauri andeach other as that is from ours. Stars are not near or far according to their brightness. 61 Cygni isa telescopic star, while Sirius, the brightest star in the heavens, is twice as far away from us. One star differs from another starin intrinsic glory. The highest testimonies to the accuracy of these celestial observationsare found in the perfect predictions of eclipses, transits of planetsover the sun, occultation of stars by the moon, and those statementsof the Nautical Almanac that enable the sailor to know exactlywhere he is on the pathless ocean by the telling of the stars:"On the trackless ocean this book is the mariner's trusted friendand counsellor; daily and nightly its revelations bring safetyto ships in all parts of the [Page 74] world. It is something morethan a mere book; it is an ever-present manifestation of the orderand harmony of the universe. " Another example of this wonderful accuracy is found in tracingthe asteroids. Within 200, 000, 000 or 300, 000, 000 miles from thesun, the one hundred and ninety-two minute bodies that have beenalready discovered move in paths very nearly the same--indeed two ofthem traverse the same orbit, being one hundred and eighty degreesapart;--they look alike, yet the eye of man in a few observationsso determines the curve of each orbit, that one is never mistakenfor another. But astronomy has higher uses than fixing time, establishing landmarks, and guiding the sailor. It greatly quickensand enlarges thought, excites a desire to know, leads to the utmostexactness, and ministers to adoration and love of the Maker ofthe innumerable suns. [Page 75]V. THE SUN. "And God made two great lights; the greater light to rule the day, andthe lesser light to rule the night: he made the stars also. "--_Gen. _i. 16. [Page 76]"It is perceived that the sun of the world, with all its essence, which is heat and light, flows into every tree, and into everyshrub and flower, and into every stone, mean as well as precious;and that every object takes its portion from this common influx, and that the sun does not divide its light and heat, and dispensea part to this and a part to that. It is similar with the sun ofheaven, from which the Divine love proceeds as heat, and the Divinewisdom as light; these two flow into human minds, as the heat andlight of the sun of the world into bodies, and vivify them accordingto the quality of the minds, each of which takes from the commoninflux as much as is necessary. "--SWEDENBORG. [Page 77]V. _THE SUN. _ Suppose we had stood on the dome of Boston Statehouse November 9th, 1872, on the night of the great conflagration, and seen the firebreak out; seen the engines dash through the streets, tracking theirpath by their sparks; seen the fire encompass a whole block, leapthe streets on every side, surge like the billows of a storm-sweptsea; seen great masses of inflammable gas rise like dark cloudsfrom an explosion, then take fire in the air, and, cut off fromthe fire below, float like argosies of flame in space. Suppose wehad felt the wind that came surging from all points of the compassto fan that conflagration till it was light enough a mile away tosee to read the finest print, hot enough to decompose the torrentsof water that were dashed on it, making new fuel to feed the flame. Suppose we had seen this spreading fire seize on the whole city, extend to its environs, and, feeding itself on the very soil, lickup Worcester with its tongues of flame--Albany, New York, Chicago, St. Louis, Cincinnati--and crossing the plains swifter than a prairiefire, making each peak of the Rocky Mountains hold up aloft a separatetorch of flame, and the Sierras whiter with heat than they ever werewith snow, the waters of the Pacific resolve into their constituentelements of oxygen and hydrogen, and [Page 78] burn withunquenchable fire! We withdraw into the air, and see below a worldon fire. All the prisoned powers have burst into intensest activity. Quiet breezes have become furious tempests. Look around this flamingglobe--on fire above, below, around--there is nothing but fire. Letit roll beneath us till Boston comes round again. No ember has yetcooled, no spire of flame has shortened, no surging cloud has beenquieted. Not only are the mountains still in flame, but other rangesburst up out of the seething sea. There is no place of rest, noplace not tossing with raging flame! Yet all this is only a feeblefigure of the great burning sun. It is but the merest hint, amillion times too insignificant. The sun appears small and quiet to us because we are so far away. Seen from the various planets, the relative size of the sun appearsas in Fig. 30. Looked for from some of the stars about us, thesun could not be seen at all. Indeed, seen from the earth, it isnot always the same size, because the distance is not always thesame. If we represent the size of the sun by one thousand on the23d of September or 21st of March, it would be represented by ninehundred and sixty-seven on the 1st of July, and by one thousandand thirty-four on the 1st of January. [Illustration: Fig. 30. --Relative Size of Sun as seen from DifferentPlanets. ] We sometimes speak of the sun as having a diameter of 860, 000 miles. We mean that that is the extent of the body as soon by the eye. But that is a small part of its real diameter. So we say the earthhas an equatorial diameter of 7925-1/2 miles, and a polar one of7899. But the air is as much a part of the earth as the rocks are. The electric currents are as much a part of the [Page 79] earth asthe ores and mountains they traverse. What the diameter of the earthis, including these, no man can tell. We used to say the airextended forty-five miles, but we now know that it reaches vastlyfarther. So of the sun, we might almost say that its diameter isinfinite, for its light and heat reach beyond our measurement. Itsliving, throbbing heart sends out pulsations, keeping all space fullof its tides of living light. [Page 80][Illustration: Fig. 31. --Zodiacal Light. ] We might say with evident truth that the far-off planets are apart of the sun, since the space they traverse is filled with thepower of that controlling king; not only with light, but also withgravitating power. But come to more ponderable matters. If we look [Page 81] into ourwestern sky soon after sunset, on a clear, moonless night in Marchor April, we shall see a dim, soft light, somewhat like themilky-way, often reaching, well defined, to the Pleiades. It iswedge-shaped, inclined to the south, and the smallest star caneasily be seen through it. Mairan and Cassini affirm that they haveseen sudden sparkles and movements of light in it. All our besttests show the spectrum of this light to be continuous, andtherefore reflected; which indicates that it is a ring of smallmasses of meteoric matter surrounding the sun, revolving with it andreflecting its light. One bit of stone as large as the end of one'sthumb, in a cubic mile, would be enough to reflect what light we seelooking through millions of miles of it. Perhaps an eye sufficientlykeen and far away would see the sun surrounded by a luminous disk, as Saturn is with his rings. As it extends beyond the earth's orbit, if this be measured as a part of the sun, its diameter would beabout 200, 000, 000 miles. Come closer. When the sun is covered by the disk of the moon atthe instant of total eclipse, observers are startled by strangeswaying luminous banners, ghostly and weird, shooting in changefulplay about the central darkness (Fig. 32). These form the corona. Men have usually been too much moved to describe them, and havealways been incapable of drawing them in the short minute or twoof their continuance. But in 1878 men travelled eight thousandmiles, coming and returning, in order that they might note thethree minutes of total eclipse in Colorado. Each man had his workassigned to him, and he was drilled to attend to that and nothingelse. Improved instruments were put into his [Page 82] hands, sothat the sun was made to do his own drawing and give his own pictureat consecutive instants. Fig. 33 is a copy of a photograph of thecorona of 1878, by Mr. Henry Draper. It showed much lesschangeability that year than common, it being very near the time ofleast sun-spot. The previous picture was taken near the time ofmaximum sun-spot. [Illustration: Fig. 32. --The Corona in 1858, Brazil. ] It was then settled that the corona consists of reflected light, sent to us from dust particles or meteoroids swirling in the vastseas, giving new densities and [Page 83] rarities, and hence thischangeful light. Whether they are there by constant projection, andfall again to the sun, or are held by electric influence, or byforce of orbital revolution, we do not know. That the corona cannotbe in any sense an atmosphere of any continuous gas, is seen fromthe fact that the comet of 1843, passing within 93, 000 miles of thebody of the sun, was not burned out of existence as a comet, nor inany perceptible degree retarded in its motion. If the sun's diameteris to include the corona, it will be from 1, 260, 000 to 1, 460, 000miles. [Illustration: Fig. 33. --The Corolla in 1878, Colorado. ] [Page 84] Come closer still. At the instant of the totality of the eclipse red flames of most fantastic shape play along the edge of the moon's disk. They can be seen at any time by the use of a proper telescope with a spectroscope attached. I have seen them with great distinctness and brilliancy with the excellent eleven-inch telescope of the Wesleyan University. A description of their appearance is best given in the language of Professor Young, of Princeton College, who has made these flames the object of most successful study. On September 7th, 1871, he was observing a large hydrogen cloud by the sun's edge. This cloud was about 100, 000 miles long, and its upper side was some 50, 000 miles above the sun's surface, the lower side some 15, 000 miles. The whole had the appearance of being supported on pillars of fire, these seeming pillars being in reality hydrogen jets brighter and more active than the substance of the cloud. At half-past twelve, when Professor Young chanced to be called away from his observatory, there were no indications of any approaching change, except that one of the connecting stems of the southern extremity of the cloud had grown considerably brighter and more curiously bent to one side; and near the base of another, at the northern end, a little brilliant lump had developed itself, shaped much like a summer thunderhead. [Illustration: Fig. 34. --Solar Prominences of Flaming Hydrogen. ] But when Professor Young returned, about half an hour later, hefound that a very wonderful change had taken place, and that avery remarkable process was actually in progress. "The whole thinghad been literally blown to shreds, " he says, "by some inconceivableuprush from beneath. In place of the quiet cloud I had [Page 87]left, the air--if I may use the expression--was filled with theflying _débris_, a mass of detached vertical fusi-form fragments, each from ten to thirty seconds (_i. E. _, from four thousand fivehundred to thirteen thousand five hundred miles) long, by two orthree seconds (nine hundred to thirteen hundred and fifty miles)wide--brighter, and closer together where the pillars had formerlystood, and rapidly ascending. When I looked, some of them hadalready reached a height of nearly four minutes (100, 000 miles); andwhile I watched them they arose with a motion almost perceptible tothe eye, until, in ten minutes, the uppermost were more than 200, 000miles above the solar surface. This was ascertained by carefulmeasurements, the mean of three closely accordant determinationsgiving 210, 000 miles as the extreme altitude attained. I amparticular in the statement, because, so far as I know, chromatospheric matter (red hydrogen in this case) has never beforebeen observed at any altitude exceeding five minutes, or 135, 000miles. The velocity of ascent, also--one hundred and sixty-sevenmiles per second--is considerably greater than anything hithertorecorded. * * * As the filaments arose, they gradually faded awaylike a dissolving cloud, and at a quarter past one only a few filmywisps, with some brighter streamers low down near thechromatosphere, remained to mark the place. But in the mean whilethe little 'thunder-head' before alluded to had grown and developedwonderfully into a mass of rolling and ever-changing flame, to speakaccording to appearances. First, it was crowded down, as it were, along the solar surface; later, it arose almost pyramidally 50, 000miles in height; then [Page 88] its summit was drawn down into longfilaments and threads, which were most curiously rolled backward andforward, like the volutes of an Ionic capital, and finally fadedaway, and by half-past two had vanished like the other. The wholephenomenon suggested most forcibly the idea of an explosion underthe great prominence, acting mainly upward, but also in alldirections outward; and then, after an interval, followed by acorresponding in-rush. " No language can convey nor mind conceive an idea of the fiercecommotion we here contemplate. If we call these movements hurricanes, we must remember that what we use as a figure moves but one hundredmiles an hour, while these move one hundred miles a second. Suchstorms of fire on earth, "coming down upon us from the north, would, in thirty seconds after they had crossed the St. Lawrence, be inthe Gulf of Mexico, carrying with them the whole surface of thecontinent in a mass not simply of ruins but of glowing vapor, inwhich the vapors arising from the dissolution of the materialscomposing the cities of Boston, New York, and Chicago would bemixed in a single indistinguishable cloud. " In the presence ofthese evident visions of an actual body in furious flame, we needhesitate no longer in accepting as true the words of St. Peterof the time "in which the [atmospheric] heavens shall pass awaywith a great noise, and the elements shall melt with fervent heat;the earth also, and the works that are therein, shall be burnedup. " This region of discontinuous flame below the corona is called thechromosphere. Hydrogen is the principal material of its upper part;iron, magnesium, and other [Page 89] metals, some of them as yetunknown on earth, but having a record in the spectrum, in the denserparts below. If these fierce fires are a part of the Sun, as theyassuredly are, its diameter would be from 1, 060, 000 to 1, 260, 000miles. Let us approach even nearer. We see a clearly recognized even disk, of equal dimensions in every direction. This is the photosphere. We here reach some definitely measurable data for estimating itsvisible size. We already know its distance. Its disk subtends anangle of 32' 12". 6, or a little more than half a degree. Threehundred and sixty such suns, laid side by side, would span thecelestial arch from east to west with a half circle of light. Twolines drawn from our earth at the angle mentioned would be 860, 000miles apart at the distance of 92, 500, 000 miles. This, then, isthe diameter of the visible and measurable part of the sun. Itwould require one hundred and eight globes like the earth in a lineto measure the sun's diameter, and three hundred and thirty-nine, to be strung like the beads of a necklace, to encircle his waist. The sun has a volume equal to 1, 245, 000 earths, but being onlyone-quarter as dense, it has a mass of only 326, 800 earths. Ithas seven hundred times the mass of all the planets, asteroids, and satellites put together. Thus it is able to control them allby its greater power of attraction. Concerning the condition of the surface of the sun many opinionsare held. That it is hot beyond all estimate is indubitable. Whethersolid or gaseous we are not sure. Opinions differ: some incline tothe first theory, others to the second; some deem the sun composedof solid particles, floating in gas so condensed [Page 90] bypressure and attraction as to shine like a solid. It has no sensiblechanges of general level, but has prodigious activity in spots. These spots have been the objects of earnest and almost hourly studyon the part of such men as Secchi, Lockyer, Faye, Young, and others, for years. But it is a long way off to study an object. No telescopebrings it nearer than 200, 000 miles. Theory after theory has beenadvanced, each one satisfactory in some points, none in all. Thefacts about the spots are these: They are most abundant on the twosides of the equator. They are gregarious, depressed below thesurface, of vast extent, black in the centre, usually surrounded bya region of partial darkness, beyond which is excessive light. Theyhave motion of their own over the surface--motion rotating about anaxis, upward and downward about the edges. They change theirapparent shape as the sun carries them across its disk by axialrevolution, being narrow as they present their edges to us, androunder as we look perpendicularly into them (Fig. 35). [Illustration: Fig. 35. --Change in Spots as rotated across the Disk, showing Cavities. ] These spots are also very variable in number, sometimes there beingnone for nearly two hundred days, and again whole years during whichthe sun is never without them. The period from minimum to maximum[Page 91] of spots is about eleven years. We might look for themagain and again in vain this year (1878). They will be most numerousin 1882 and 1893. The cause of this periodicity was inferred to bethe near approach of the enormous planet Jupiter, causingdisturbance by its attraction. But the periods do not correspond, and the cause is the result of some law of solar action to us as yetunknown. These spots may be seen with almost any telescope, the eye beingprotected by deeply colored glasses. Until within one hundred years they were supposed to be islands ofscoriæ floating in the sea of molten matter. But they were depressedbelow the surface, and showed a notch when on the edge. Wilsonoriginated and Herschel developed the theory that the sun's realbody was dark, cool, and habitable, and that the photosphere wasa luminous stratum at a distance from the real body, with openingsshowing the dark spots below. Such a sun would have cooled off ina week, but would previously have annihilated all life below. The solar spots being most abundant on the two sides of the equator, indicates their cyclonic character; the centre of a cyclone israrefied, and therefore colder, and cold on the sun is darkness. M. Faye says: "Like our cyclones, they are descending, as I haveproved by a special study of these terrestrial phenomena. Theycarry down into the depths of the solar mass the cooler materialsof the upper layers, formed principally of hydrogen, and thus producein their centre a decided extinction of light and heat as long asthe gyratory movement continues. Finally, the hydrogen set freeat the base of the whirlpool becomes reheated at this [Page 92]great depth, and rises up tumultuously around the whirlpool, formingirregular jets, which appear above the chromosphere. These jetsconstitute the protuberances. The whirlpools of the sun, like thoseon the earth, are of all dimensions, from the scarcely visible poresto the enormous spots which we see from time to time. They have, like those of the earth, a marked tendency, first to increase andthen to break up, and thus form a row of spots extending along thesame parallel. " [Illustration: Fig. 36. --Solar spot, by Langley. ] A spot of 20, 000 miles diameter is quite small; there was one 14, 816miles across, visible to the naked eye for a week in 1843. Thisparticular sun-spot somewhat [Page 93] helped the Millerites. On theday of the eclipse, in 1858, a spot over 107, 000 miles in extent wasclearly seen. In such vast tempests, if there were ships built aslarge as the whole earth, they would be tossed like autumn leaves inan ocean storm. The revolution of the sun carries a spot across its face in aboutfourteen days. After a lapse of as much more time, they often reappearon the other side, changed but recognizable. They often break ontor disappear under the eye of the observer. They divide like apiece of ice dropped on a frozen pond, the pieces sliding off inevery direction, or combine like separate floes driven togetherinto a pack. Sometimes a spot will last for more than two hundreddays, recognizable through six or eight revolutions. Sometimesa spot will last only half an hour. The velocities indicated by these movements are incredible. Anup-rush and down-rush at the sides has been measured of twentymiles a second; a side-rush or whirl, of one hundred and twentymiles a second. These tempests rage from a few days to half a year, traversing regions so wide that our Indian Ocean, the realm ofstorms, is too small to be used for comparison; then, as they cease, the advancing sides of the spots approach each other at the rate of20, 000 miles an hour; they strike together, and the rising sprayof fire leaps thousands of miles into space. It falls again into theincandescent surge, rolls over mountains as the sea over pebbles, andall this for eon after eon without sign of exhaustion or diminution. All these swift succeeding Himalayas of fire, where one hundredworlds could be buried, do not usually prevent the sun's appearingto our far-off eyes as a perfect sphere. [Page 94]_What the Sun does for us. _ To what end does this enormous power, this central source of power, exist? That it could keep all these gigantic forces within itselfcould not be expected. It is in a system where every atom is madeto affect every other atom, and every world to influence everyother. The Author of all lives only to do good, to send rain onthe just and unjust, to cause his sun to rise on the evil and thegood, and to give his spirit, like a perpetually widening river, to every man to profit withal. The sun reaches his unrelaxing hand of gravitation to every otherworld at every instant. The tendency of every world is to fly offin a straight line. This tendency must be momentarily curbed, andthe planet held in its true curve about the sun. These giant worldsmust be perfectly handled. Their speed, amounting to seventy timesas fast as that of a rifle-ball, must be managed. Each and everyworld may be said to be lifted momentarily and swung perpetuallyat arm's-length by the power of the sun. The sun warms us. It would convey but a small idea of the truthto state how many hundreds of millions of cubic miles of ice couldbe hailed at the sun every second without affecting its heat; but, if any one has any curiosity to know, it is 287, 200, 000 cubic milesof ice per second. We journey through space which has a temperature of 200° belowzero; but we live, as it were, in a conservatory, in the midst ofperpetual winter. We are roofed over by the air that treasures theheat, floored under by strata both absorptive and retentive of heat, [Page 95] and between the earth and air violets grow and grainsripen. The sun has a strange chemical power. It kisses the coldearth, and it blushes with flowers and matures the fruit and grain. We are feeble creatures, and the sun gives us force. By it the lightwinds move one-eighth of a mile an hour, the storm fifty miles, thehurricane one hundred. The force is as the square of the velocity. It is by means of the sun that the merchant's white-sailed ships areblown safely home. So the sun carries off the miasma of the marsh, the pollution of cities, and then sends the winds to wash andcleanse themselves in the sea-spray. The water-falls of the earthturn machinery, and make Lowells and Manchesters possible, becausethe sun lifted all that water to the hills. Intermingled with these currents of air are the currents of electricpower, all derived from the sun. These have shown their swiftnessand willingness to serve man. The sun's constant force displayedon the earth is equal to 543, 000, 000, 000 engines of 400-horse powereach, working day and night; and yet the earth receives only1/21500000000 part of the whole force of the sun. Besides all this, the sun, with provident care, has made and givento us coal. This omnipotent worker has stored away in past agesan inexhaustible reservoir of his power which man may easily mineand direct, thus releasing himself from absorbing toil. EXPERIMENTS. Any one may see the spots on the sun who has a spy-glass. Darkenthe room and put the glass through an opening toward the sun, asshown in Fig. 37. The eye-piece should be drawn out about halfan inch beyond [Page 96] its usual focusing for distant objects. Thefarther it is drawn, the nearer must we hold the screen for aperfect image. By holding a paper near the eye-piece, the proper direction ofthe instrument may be discovered without injury to the eyes. Bythis means the sun can be studied from day to day, and its spots orthe transits of Mercury and Venus shown to any number of spectators. [Illustration: Fig. 37. --Holding Telescope to see the Sun's Spots. ] First covering the eyes with very dark or smoked glasses, erecta disk of pasteboard four inches in diameter between you and thesun; close one eye; stand near it, and the whole sun is obscured. Withdraw from it till the sun's rays just shoot over the edge ofthe disk on every side. Measure the distance from the eye to thedisk. You will be able to determine the distance of the sun bythe rule of three: thus, as four inches is to 860, 000 miles, sois distance from eye to disk to distance from disk to the sun. Take such measurements at sunrise, noon, and sunset, and see theapparently differing sizes due to refraction. [Page 97]VI. THE PLANETS, AS SEEN FROM SPACE. "He hangeth the earth upon nothing. "--_Job_ xxvi. 7. [Page 98]"Let a power be delegated to a finite spirit equal to the projectionof the most ponderous planet in its orbit, and, from an exhaustlessmagazine, let this spirit select his grand central orb. Let him withpuissant arm locate it in space, and, obedient to his mandate, therelet it remain forever fixed. He proceeds to select his planetaryglobes, which he is now required to marshal in their appropriateorder of distance from the sun. Heed well this distribution; forshould a single globe be misplaced, the divine harmony is destroyedforever. Let us admit that finite intelligence may at length determinethe order of combination; the mighty host is arrayed in order. These worlds, like fiery coursers, stand waiting the command tofly. But, mighty spirit, heed well the grand step, ponder wellthe direction in which thou wilt launch each wailing world; weighwell the mighty impulse soon to be given, for out of the myriadsof directions, and the myriads of impulsive forces, there comesbut a single combination that will secure the perpetuity of yourcomplex scheme. In vain does the bewildered finite spirit attemptto fathom this mighty depth. In vain does it seek to resolve thestupendous problem. It turns away, and while endued with omnipotentpower, exclaims, 'Give to me infinite wisdom, or relieve me fromthe impossible task!'"-0. M. MITCHEL, LL. D. [Page 99]VI. _THE PLANETS, AS SEEN FROM SPACE_ If we were to go out into space a few millions of miles from eitherpole of the sun, and were endowed with wonderful keenness of vision, we should perceive certain facts, viz: That space is frightfullydark except when we look directly at some luminous body. There isno air to bend the light out of its course, no clouds or otherobjects to reflect it in a thousand directions. Every star is abrilliant point, even in perpetual sunshine. The cold is frightfulbeyond the endurance of our bodies. There is no sound of voice inthe absence of air, and conversation by means of vocal organs beingimpossible, it must be carried on by means of mind communication. We see below an unrevolving point on the sun that marks its pole. Ranged round in order are the various planets, each with its axispointing in very nearly the same direction. All planets, exceptpossibly Venus, and all moons except those of Uranus and Neptune, present their equators to the sun. The direction of orbital andaxial revolution seen from above the North Pole would be oppositeto that of the hands of a watch. [Illustration: Fig. 38. --Orbits and Comparative Sizes of the Planets. ] The speed of this orbital revolution must be proportioned to thedistance from the sun. The attraction of the sun varies inverselyas the square of the distance. [Page 100] It holds a planet with acertain power; one twice as far off, with one-fourth that power. This attraction must be counterbalanced by centrifugal force; greatforce from great speed when attraction is great, and small from less[Page 101] speed when attractive power is diminished by distance. Hence Mercury must go 29. 5 miles per second--seventy times as fastas a rifle-ball that goes two-fifths of a mile in a second--or bedrawn into the sun; while Neptune, seventy-five times as far off, and hence attracted only 1/5626 as much, must be slowed down to 3. 4miles a second to prevent its flying away from the feeblerattraction of the sun. The orbital velocity of the various planetsin miles per second is as follows: Mercury 29. 55 | Jupiter 8. 06 Venus 21. 61 | Saturn 5. 95 Earth 18. 38 | Uranus 4. 20 Mars 14. 99 | Neptune 3. 36 Hence, while the earth makes one revolution in its year, Mercuryhas made over four revolutions, or passed through four years; theslower Neptune has made only 1/164 of one revolution. The time of axial revolution which determines the length of theday varies with different planets. The periods of the four planetsnearest the sun vary only half an hour from that of the earth, while the enormous bodies of Jupiter and Saturn revolve in tenand ten and a quarter hours respectively. This high rate of speed, and its resultant, centrifugal force, has aided in preventing thesebodies from becoming as dense as they would otherwise be--Jupiterbeing only 0. 24 as dense as the earth, and Saturn only 0. 13. Thisextremely rapid revolution produces a great flattening at the poles. If Jupiter should rotate four times more rapidly than it does, itcould not be held together compactly. As it is, the polar diameteris five thousand miles less than the equatorial: the differencein diameters produced by the [Page 102] same cause on the earth, owing to the slower motion and smaller mass, being only twenty-sixmiles. The effect of this will be more specifically treatedhereafter. The difference in the size of the planets is very noticeable. Ifwe represent the sun by a gilded globe two feet in diameter, wemust represent Vulcan and Mercury by mustard-seeds; Venus, by apea; Earth, by another; Mars, by one-half the size; Asteroids, bythe motes in a sunbeam; Jupiter, by a small-sized orange; Saturn, by a smaller one; Uranus, by a cherry; and Neptune, by one a littlelarger. Apply the principle that attraction is in proportion to the mass, and a man who weighs one hundred and fifty pounds on the earthweighs three hundred and ninety-six on Jupiter, and only fifty-eighton Mars; while on the Asteroids he could play with bowlders formarbles, hurl hills like Milton's angels, leap into the fifth-storywindows with ease, tumble over precipices without harm, and goaround the little worlds in seven jumps. [Illustration: Fig. 39. --Orbit of Earth, showing Parallelism ofAxis and Seasons. ] The seasons of a planet are caused by the inclination of its axisto the plane of its orbit. In Fig. 39 the rotating earth is seenat A, with its northern pole turning in constant sunlight, andits southern pole in constant darkness; everywhere south of theequator is more darkness than day, and hence winter. Passing onto B, the world is seen illuminated equally on each side of theequator. Every place has its twelve hours' darkness and light ateach revolution. But at C--the axis of the earth always preservingthe same direction--the northern pole is shrouded in continualgloom. Every place [Page 105] north of the equator gets moredarkness than light, and hence winter. The varying inclination of the axes of the different planets givesa wonderful variety to their seasons. The sun is always nearlyover the equator of Jupiter, and every place has nearly its fivehours day and five hours night. The seasons of Earth, Mars, andSaturn are so much alike, except in length, that no comment isnecessary. The ice-fields at either pole of Mars are observed toenlarge and contract, according as it is winter or summer there. Saturn's seasons are each seven and a half years long. The alternatedarkness and light at the poles is fifteen years long. But the seasons of Venus present the greatest anomaly, if its assignedinclination of axis (75°) can be relied on as correct, which isdoubtful. Its tropic zone extends nearly to the pole, and at thesame time the winter at the other pole reaches the equator. Theshort period of this planet causes it to present the south pole tothe sun only one hundred and twelve days after it has been scorchingthe one at the north. This gives two winters, springs, summers, andautumns to the equator in two hundred and twenty-five days. If each whirling world should leave behind it a trail of light tomark its orbit, and our perceptions of form were sufficiently acute, we should see that these curves of light are not exact circles, buta little flattened into an ellipse, with the sun always in oneof the foci. Hence each planet is nearer to the sun at one partof its orbit than another; that point is called the perihelion, and the farthest point aphelion. This eccentricity of orbit, ordistance of the sun from the centre, is very small. [Page 106] Inthe case of Venus it is only . 007 of the whole, and in no instanceis it more than . 2, viz. , that of Mercury. This makes the sun appeartwice as large, bright, and hot as seen and felt on Mercury at itsperihelion than at its aphelion. The earth is 3, 236, 000 miles nearerto the sun in our winter than summer. Hence the summer in thesouthern hemisphere is more intolerable than in the northern. Butthis eccentricity is steadily diminishing at a uniform rate, byreason of the perturbing influence of the other planets. In the caseof some other planets it is steadily increasing, and, if it were togo on a sufficient time, might cause frightful extremes oftemperature; but Lalande has shown that there are limits at which itis said, "Thus far shalt thou go, and no farther. " Then acompensative diminution will follow. Conceive a large globe, to represent the sun, floating in a roundpond. The axis will be inclined 7-1/2° to the surface of the water, one side of the equator be 7-1/2° below the surface, and the otherside the same distance above. Let the half-submerged earth sailaround the sun in an appropriate orbit. The surface of the waterwill be the plane of the orbit, and the water that reaches outto the shore, where the stars would be set, will be the plane ofthe ecliptic. It is the plane of the earth's orbit extended tothe stars. The orbits of all the planets do not lie in the same plane, butare differently inclined to the plane of the ecliptic, or the planeof the earth's orbit. Going out from the sun's equator, so as tosee all the orbits of the planets on the edge, we should see theminclined to that of the earth, as in Fig. 40. [Illustration: Fig. 40. --Inclination of the Planes of Orbits. ] If the earth, and Saturn, and Pallas were lying in [Page 107] thesame direction from the sun, and the outer bodies were to start in adirect line for the sun, they would not collide with the earth ontheir way; but Saturn would pass 4, 000, 000 and Pallas 50, 000, 000miles over our heads. From this same cause we do not see Venus andMercury make a transit across the disk of the sun at everyrevolution. [Illustration: Fig. 41. --Inclination of Orbits of Venus and Earth. Nodal Line, D B. ] Fig. 41 shows a view of the orbits of the earth and Venus seennot from the edge but from a position somewhat above. The point E, where Venus crosses the plane of the earth's orbit, is called theascending node. If the earth were at B when Venus is at E, Venuswould be seen on the disk of the sun, making a transit. The samewould be true if the earth were at D, and Venus at the descendingnode F. This general view of the flying spheres is full of interest. [Page108] While quivering themselves with thunderous noises, all issilent about them; earthquakes may be struggling on their surfaces, but there is no hint of contention in the quiet of space. They aretoo distant from one another to exchange signals, except, perhaps, the fleet of asteroids that sail the azure between Mars and Jupiter. Some of these come near together, continuing to fill each other'ssky for days with brightness, then one gradually draws ahead. Theyhave all phases for each other--crescent, half, full, and gibbous. These hundreds of bodies fill the realm where they are withinexhaustible variety. Beyond are vast spaces--cold, dark, void ofmatter, but full of power. Occasionally a little spark of lightlooms up rapidly into a world so huge that a thousand of our earthscould not occupy its vast bulk. It swings its four or eight moonswith perfect skill and infinite strength; but they go by and leavethe silence unbroken, the darkness unlighted for years. Nevertheless, every part of space is full of power. Nowhere in itswide orbit can a world find a place; at no time in its eons offlight can it find an instant when the sun does not hold it insafety and life. _The Outlook from the Earth. _ If we come in from our wanderings in space and take an outlook fromthe earth, we shall observe certain movements, easily interpretednow that we know the system, but nearly inexplicable to men whonaturally supposed that the earth was the largest, most stable, and central body in the universe. We see, first of all, sun, moon, and stars rise in the east, mountthe heavens, and set in the west. As I [Page 109] revolve in mypivoted study-chair, and see all sides of the room--library, maps, photographs, telescope, and windows--I have no suspicion that it isthe room that whirls; but looking out of a car-window in a depot atanother car, one cannot tell which is moving, whether it be his caror the other. In regard to the world, we have come to feel itswhirl. We have noticed the pyramids of Egypt lifted to hide the sun;the mountains of Hymettus hurled down, so as to disclose the moonthat was behind them to the watchers on the Acropolis; and themighty mountains of Moab removed to reveal the stars of the east. Train the telescope on any star; it must be moved frequently, or theworld will roll the instrument away from the object. Suspend acannon-ball by a fine wire at the equator; set it vibrating northand south, and it swings all day in precisely the same direction. But suspend it directly over the north pole, and set it swingingtoward Washington; in six hours after it is swinging toward Rome, inItaly; in twelve hours, toward Siam, in Asia; in nineteen hours, toward the Sandwich Islands; and in twenty-four, toward Washingtonagain, not because it has changed the plane of its vibration, butbecause the earth has whirled beneath it, and the torsion of thewire has not been sufficient to compel the plane of the originaldirection to change with the turning of the earth. The law ofinertia keeps it moving in the same direction. The same experimentalproof of revolution is shown in a proportional degree at any pointbetween the pole and the equator. But the watchers on the Acropolis do not get turned over so as tosee the moon at the same time every night. [Page 110] We turn downour eastern horizon, but we do not find fair Luna at the same momentwe did the night before. We are obliged to roll on for some thirtyto fifty minutes longer before we find the moon. It must be going inthe same direction, and it takes us longer to get round to it thanif if it were always in the same spot; so we notice a star near themoon one night--it is 13° west of the moon the next night. The moonis going around the earth from west to east, and if it goes 13° inone day, it will take a little more than twenty-seven days to go theentire circle of 360°. [Illustration: Fig. 42. --Showing the Sun's Movement among the Stars. ] [Page 111]In our outlook we soon observe that we do not by our revolutioncome to see the same stars rise at the same hour every night. Orionand the Pleiades, our familiar friends in the winter heavens, aregone from the summer sky. Have they fled, or are we turned fromthem? This is easily understood from Fig. 42. When the observer on the earth at A looks into the midnight skyhe sees the stars at E; but as the earth passes on to B, he seesthose stars at E three minutes sooner every night; and at midnightthe stars at F are over his head. Thus in a year, by going aroundthe sun, we have every star of the celestial dome in our midnightsky. We see also how the sun appears among the successiveconstellations. When we are at A, we see the sun among the starsat G; but as we move toward B, the sun appears to move toward H. If we had observed the sun rise on the 20th of August, 1876, weshould have seen it rise a little before Regulus, and a littlesouth of it, in such a relation as circle 1 is to the star in Fig. 43. By sunset the earth had moved enough to make the sun appearto be at circle 2, and by the next morning at circle 3, at whichtime Regulus would rise before the sun. Thus the earth's motionseems to make the sun traverse a regular circle among the starsonce a year: but it is not the sun that moves. [Illustration: Fig. 43. ] There are certain stars that have such irregular, uncertain, vagariousways that they were called vagabonds, or planets, by the earlyastronomers. Here is the path of Jupiter in the year 1866 (Fig. 44). These bodies go forward for awhile, then stop, start aside, then retrograde, [Page 112] and go on again. Some are never seen farfrom the sun, and others in all parts of the ecliptic. [Illustration: Fig. 44. ] First see them as they stand to-day, as in Fig. 45. The observerstands on the earth at A. It has rolled over so far that he cannotsee the sun; it has set. But Venus is still in sight; Jupiter is45° behind Venus, and Saturn is seen 90° farther east. When A hasrolled a little farther, if he is awake, he will see Mars beforehe sees the sun; or, in common language, Venus will set after, and Mars rise before the sun. All these bodies at near and fardistances seem set in the starry dome, as the different stars seemin Fig. 42, p. 110. [Illustration: Fig. 45. Showing Position of Planets. ] The mysterious movements of advance and retreat are renderedintelligible by Fig. 46. The planet Mercury is at A, and, seen fromthe earth, B is located at _a_, [Page 113] on the background of thestars it seems to be among. It remains apparently stationary at _a_for some time, because approaching the earth in nearly a straightline. Passing D to C, it appears to retrograde among the stars to_c_; remains apparently stationary for some time, then, in passingfrom C to E and A, appears to pass back among the stars to _a_. Theprogress of the earth, meanwhile, although it greatly retards theapparent motion from A to C, greatly hastens it from C to A. [Illustration: Fig. 46. --Apparent Movements of an Inferior Planet. ] It is also apparent that Mercury and Venus, seen from the earth, can never appear far from the sun. They must be just behind thesun as evening stars, or just before it as heralds of the morning. Venus is never more than 47° from the sun, and Mercury never morethan 30°; indeed, it keeps so near the sun that very few peoplehave ever seen the brilliant sparkler. Observe how much larger theplanet appears near the earth in conjunction at D than in oppositionat E. Observe also what phases it must present, and how transitssometimes take place. [Page 114]The movement of a superior planet, one whose orbit is exteriorto the earth, is clear from Fig. 47. When the earth is at A andMars at B, it will appear among the stars at C. When the earth isat D, Mars having moved more slowly to E, will have retrogradedto F. It remains there while the earth passes on, in a line nearlystraight, from Mars to G; then, as the earth begins to curve aroundthe sun, Mars will appear to retraverse the distance from F toC, and beyond. The farther the superior planet is from the earththe less will be the retrograde movement. [Illustration: Fig. 47. --Illustrating Movements of a Superior Planet. ] The reader should draw the orbits in proportion, and, rememberingthe relative speed of each planet, note the movement of each indifferent parts of their orbits. To account for these most simple movements, the earlier astronomersinvented the most complex and impossible machinery. They thought theearth the centre, and that the sun, moon, and stars were carriedabout it, as stoves around a person to warm him. They thought thesestrange movements of the planets were accomplished by mounting themon subsidiary eccentric wheels in the revolving crystal sphere. All that was [Page 115] needed to give them a right conception was asinking of their world and themselves to an appropriate proportion, and an enlargement of their vision, to take in from an exaltedstand-point a view of the simplicity of the perfect plan. EXPERIMENTS. Fix a rod, or tube, or telescope pointing at a star in the castor west, and the earth's revolution will be apparent in a moment, turning the tube away from the star. Point it at stars about thenorth pole, and those on one side will be found going in an oppositedirection from those on the other, and very much slower than thoseabout the equator. Anyone can try the pendulum experiment who hasaccess to some lofty place from which to suspend the ball. It wastried in Bunker Hill Monument a few years ago, and is to be triedin Paris, in the summer of 1879, with a seven-hundred-pound pendulumand a suspending wire seventy yards long. The advance and retrogrademovements of planets can be illustrated by two persons walkingaround a centre and noticing the place where the person appearsprojected on the wall beyond. * * * * * PROCESSION OF STARS AND SOULS. "I stood upon the open casement, And looked upon the night, And saw the westward-going stars Pass slowly out of sight. "Slowly the bright procession Went down the gleaming arch, And my soul discerned the music Of the long triumphal march; "Till the great celestial army, Stretching far beyond the poles, Became the eternal symbol Of the mighty march of souls. [Page 116] "Onward, forever onward, Red Mars led on his clan; And the moon, like a mailèd maiden, Was riding in the van. "And some were bright in beauty, And some were faint and small, But these might be, in their great heights, The noblest of them all. "Downward, forever downward, Behind earth's dusky shore, They passed into the unknown night-- They passed, and were no more. "No more! Oh, say not so! And downward is not just; For the sight is weak and the sense is dim That looks through heated dust. "The stars and the mailèd moon, Though they seem to fall and die, Still sweep in their embattled lines An endless reach of sky. "And though the hills of Death May hide the bright array, The marshalled brotherhood of souls Still keeps its onward way. "Upward, forever upward, I see their march sublime, And hear the glorious music Of the conquerors of Time. "And long let me remember That the palest fainting one May to diviner vision be A bright and blazing sun. " THOMAS BUCHANAN READ. [Page 117]VII. SHOOTING-STARS, METEORS, AND COMETS. "The Lord cast down great stones from heaven upon them unto Azekah, and they died. "--_Joshua_ x. II. [Page 118][Illustration: A SWARM OF METEORS MEETING THE EARTH. Their orbits are all parallel. Those coming in direct line to theeye appear as stars, having no motion. Those on one side of thisline are seen in foreshortened perspective. Those furthest fromthe centre, other things being equal, appear longest. The centre, called the radiant point, of these November meteors is situatedin Leo; that of the August meteors in Perseus. Over fifty suchradiant points have been discovered. Over 30, 000 meteors have beenvisible in an hour. ] [Page 119]VII. _SHOOTING-STARS, METEORS, AND COMETS. _ Before particularly considering the larger aggregations of mattercalled planets or worlds as individuals, it is best to investigatea part of the solar system consisting of smaller collections ofmatter scattered everywhere through space. They are of variousdensities, from a cloudlet of rarest gas to solid rock; of varioussizes, from a grain's weight to little worlds; of various relationsto each other, from independent individuality to related streamsmillions of miles long. When they become visible they are calledshooting-stars, which are evanescent star-points darting throughthe upper air, leaving for an instant a brilliant train; meteors, sudden lights, having a discernible diameter, passing over a largeextent of country, often exploding with violence (Fig. 48), andthrowing down upon the earth aerolites; and comets, vast extentsof ghostly light, that come we know not whence and go we know notwhither. All these forms of matter are governed by the same lawsas the worlds, and are an integral part of the solar system--apart of the unity of the universe. [Illustration: Fig. 48. --Explosion of a Bolide. ] Everyone has seen the so-called shooting-stars. They break outwith a sudden brilliancy, shoot a few degrees with quiet speed, and are gone before we can say, "See there!" The cause of theirappearance, the [Page 120] conversion of force into heat by theircontact with our atmosphere, has been already explained. Other factsremain to be studied. They are found to appear about seventy-threemiles above the earth, and to disappear about twenty miles nearerthe surface. Their average velocity, thirty-five, sometimes rises toone hundred miles a second. They exhibit different colors, accordingto their different chemical substances, which are consumed. Thenumber of them to be seen on different nights is exceedinglyvariable; sometimes not more [Page 121] than five or six an hour, and sometimes so many that a man cannot count those appearing in asmall section of sky. This variability is found to be periodic. There are everywhere in space little meteoric masses of matter, fromthe weight of a grain to a ton, and from the density of gas to rock. The earth meets 7, 500, 000 little bodies every day--there iscollision--the little meteoroid gives out its lightning sign ofextinction, and, consumed in fervent heat, drops to the earth as gasor dust. If we add the number light enough to be seen by atelescope, they cannot be less than 400, 000, 000 a day. Everywhere wego, in a space as large as that occupied by the earth and itsatmosphere, there must be at least 13, 000 bodies--one in 20, 000, 000cubic miles--large enough to make a light visible to the naked eye, and forty times that number capable of revealing themselves totelescopic vision. Professor Peirce is about to publish, as thestartling result of his investigations, "that the heat which theearth receives directly from meteors is the same in amount which itreceives from the sun by radiation, and that the sun receivesfive-sixths of its heat from the meteors that fall upon it. " [Illustration: Fig. 49. --Bolides. ] [Page 121]In 1783 Dr. Schmidt was fortunate enough to have a telescopic viewof a system of bodies which had turned into meteors. These were twolarger bodies followed by several smaller ones, going in parallellines till they were extinguished. They probably had been revolvingabout each other as worlds and satellites before entering ouratmosphere. It is more than probable that the earth has many suchbodies, too small to be visible, revolving around it as moons. [Illustration: Fig. 50. --Santa Rosa Aerolite. ] _Aerolites. _ Sometimes the bodies are large enough to bear the heat, and theunconsumed centre comes to the earth. [Page 123] Their velocity hasbeen lessened by the resisting air, and the excessive heatdiminished. Still, if found soon after their descent, they are toohot to be handled. These are called aerolites or air-stones. Therewas a fall in Iowa, in February, 1875, from which fragmentsamounting to five hundred pounds weight were secured. On the eveningof December 21st, 1876, a meteor of unusual size and brilliancypassed over the states of Kansas, Missouri, Illinois, Indiana, andOhio. It was first seen in the western part of Kansas, at analtitude of about sixty miles. In crossing the State of Missouri itbegan to explode, and this breaking up continued while passingIllinois, Indiana, and Ohio, till it consisted of a large flock ofbrilliant balls chasing each other across the sky, the number beingvariously estimated at from twenty to one hundred. It wasaccompanied by terrific explosions, and was seen along a path of notless than a thousand miles. When first seen in Kansas, it is said tohave appeared as large as the full moon, and with a train fromtwenty-five to one hundred feet long. Another, very similar inappearance and behavior, passed over a part of the same course inFebruary, 1879. At Laigle, France, on April 26th, 1803, about oneo'clock in the day, from two to three thousand fell. The largest didnot exceed seventeen pounds weight. One fell in Weston, Connecticut, in 1807, weighing two hundred pounds. A very destructive shower ismentioned in the book of Joshua, chap. X. Ver. 11. These bodies are not evenly distributed through space. In someplaces they are gathered into systems which circle round the sunin orbits as certain as those of the [Page 124] planets. The chainof asteroids is an illustration of meteoric bodies on a large scale. They are hundreds in number--meteors are millions. They have theirregion of travel, and the sun holds them and the giant Jupiter bythe same power. The Power that cares for a world cares for asparrow. If their orbit so lies that a planet passes through it, andthe planet and the meteors are at the point of intersection at thesame time, there must be collisions, and the lightning signs ofextinction proportioned to the number of little bodies in a givenspace. It is demonstrated that the earth encounters more than one hundredsuch systems of meteoric bodies in a single year. It passes throughone on the 10th of August, another on the 11th of November. Ina certain part of the first there is an agglomeration of bodiessufficient to become visible as it approaches the sun, and this isknown as the comet of 1862; in the second is a similar agglomeration, known as Temple's comet. It is repeating the same thing to say thatmeteoroids follow in the train of the comets. The probable orbitof the November meteors and the comet of 1866 is an exceedinglyelongated ellipse, embracing the orbit of the earth at one end anda portion of the orbit of Uranus at the other (Fig. 51). That ofthe August meteors and the comet of 1862 embraces the orbit ofthe earth at one end, and thirty per cent. Of the other end isbeyond the orbit of Neptune. [Illustration: Fig. 51. --Orbit of the November Meteors and the Cometor 1866. ] In January, 1846, Biela's comet was observed to be divided. Atits next return, in 1852, the parts were 1, 500, 000 miles apart. They could not be found on their periodic returns in 1859, 1865, and 1872; but it [Page 125] should have crossed the earth's orbitearly in September, 1872. The earth itself would arrive at the pointof crossing two or three months later. If the law of revolutionheld, we might still expect to find some of the trailing meteoroidsof the comet not gone by on our arrival. It was shown that the pointof the earth that would strike them would be toward a certain placein the constellation of Andromeda, if the remains of the dilutedcomet were still there. The prediction was verified in everyrespect. At the appointed time, place, [Page 126] and direction, thestreaming lights were in our sky. That these little bodies belongedto the original comet none can doubt. By the perturbations ofplanetary attraction, or by different original velocities, a cometmay be lengthened into an invisible stream, or an invisible streamagglomerated till it is visible as a comet. _Comets. _ Comets will be most easily understood by the foregoing considerations. They are often treated as if they were no part of the solar system;but they are under the control of the same laws, and owe theirexistence, motion, and continuance to the same causes as Jupiter andthe rest of the planets. They are really planets of wider wandering, greater ellipticity, and less density. They have periodic timesless than the earth, and fifty times as great as Neptune. Theyare little clouds of gas or meteoric matter, or both, darting intothe solar system from every side, at every angle with the planeof the ecliptic, becoming luminous with reflected light, passingthe sun, and returning again to outer darkness. Sometimes theyhave no tail, having a nucleus surrounded by nebulosity like adim sun with zodiacal light; sometimes one tail, sometimes half adozen. These follow the comet to perihelion, and precede it afterward(Fig. 52). The orbits of some comets are enormously elongated; oneend may lie inside the earth's orbit, and the other end be as farbeyond Neptune as that is from the sun. Of course only a smallpart of such a curve can be studied by us: the comet is visibleonly when near the sun. The same curve around the sun may be anorbit that will bring it back again, [Page 127] or one that willcarry it off into infinite space, never to return. One rate of speedon the curve indicates an elliptical orbit that returns; a greaterrate of speed indicates that it will take a parabolic orbit, whichnever returns. The exact rate of speed is exceedingly difficult todetermine; hence it cannot be confidently asserted that any cometever visible will not return. They may all belong to the solarsystem; but some will certainly be gone thousands of years beforetheir fiery forms will greet the watchful eyes of dwellers on theearth. A comet that has an elliptic orbit may have it changed to[Page 128] parabolic by the accelerations of its speed, byattracting planets; or a parabolic comet may become elliptic, and sopermanently attracted to the system by the retardations ofattracting bodies. A comet of long period may be changed to one ofshort period by such attraction, or _vice versa_. [Illustration: Fig. 52. --Aspects of Remarkable Comets. ] The number of comets, like that of meteor streams, is exceedinglylarge. Five hundred have been visible to the naked eye since theChristian era. Two hundred have been seen by telescopes inventedsince their invention. Some authorities estimate the number belongingto our solar system by millions; Professor Peirce says more thanfive thousand millions. _Famous Comets. _ The comet of 1680 is perhaps the one that appeared in A. D. 44, soonafter the death of Julius Cæsar, also in the reign of Justinian, A. D. 531, and in 1106. This is not determined by any recognizableresemblance. It had a tail 70° long; it was not all arisen whenits head reached the meridian. It is possible, from the shape ofits orbit, that it has a periodic time of nine thousand years, orthat it may have a parabolic orbit, and never return. Observationstaken two hundred years ago have not the exactness necessary todetermine so delicate a point. On August 19th, 1682, Halley discovered a comet which he soon declaredto be one seen by Kepler in 1607. Looking back still farther, hefound that a comet was seen in 1531 having the same orbit. Stillfarther, by the same exact period of seventy-five years, he foundthat it was the same comet that had disturbed [Page 129] theequanimity of Pope Calixtus in 1456. Calculations were undertaken asto the result of all the accelerations and retardations by theattractions of all the planets for the next seventy-five years. There was not time to finish all the work; but a retardation of sixhundred and eighteen days was determined, with a possible error ofthirty days. The comet actually came to time within thirty-threedays, on March 12th, 1759. Again its return was calculated with morelaborious care. It came to time and passed the sun within three daysof the predicted time, on the 16th of November, 1835. It passed fromsight of the most powerful telescopes the following May, and hasnever since been seen by human eye. But the eye of science sees itas having passed its aphelion beyond the orbit of Neptune in 1873, and is already hastening back to the warmth and light of the sun. Itwill be looked for in 1911; and there is good hope of predicting, long before it is seen, the time of its perihelion within a day. _Biela's lost Comet. _--This was a comet with a periodic time ofsix years and eight months. It was observed in January, 1846, tohave separated into two parts of unequal brightness. The lesserpart grew for a month until it equalled the other, then becamesmaller and disappeared, while the other was visible a month longer. At disappearance the parts were 200, 000 miles asunder. On its nextreturn, in 1852, the parts were 1, 500, 000 miles apart; sometimesone was brighter and sometimes the other; which was the fragmentand which was the main body could not be recognized. They vanishedin September, 1852, and have never been seen since. Three revolutionshave been made since that time, but no [Page 130] trace of it couldbe discovered. Probably the same influence that separated it intoparts, separated the particles till too thin and tenuous to be seen. There is ground for believing that the earth passed through a partof it, as before stated under the head of meteors. _The Great Comet of_ 1843 passed nearer the sun than any knownbody. It almost grazed the sun. If it ever returns, it will be inA. D. 2373. _Donati's Comet of_ 1858. --This was one of the most magnificentof modern times. During the first three months it showed no tail, but from August to October it had developed one forty degrees inlength. Its period is about two thousand years. Every reader remembersthe comet of the summer of 1875. _Encke's Comet. _--This comet has become famous for its supposedconfirmation of the theory that space was filled with a substanceinfinitely tenuous, which resisted the passage of this gaseousbody in an appreciable degree, and in long ages would so retardthe motion of all the planets that gravitation would draw themall one by one into the sun. We must not be misled by the termretardation to suppose it means behind time, for a retarded bodyis before time. If its velocity is diminished, the attraction ofthe sun causes it to take a smaller orbit, and smaller orbits meanincreased speed--hence the supposed retardation would shorten itsperiodic time. This comet was thought to be retarded two and ahalf hours at each revolution. If it was, it would not prove theexistence of the resisting medium. Other causes, unknown to us, might account for it. Subsequent and more exact calculations failto find any retardations in at least two revolutions between 1865and [Page 131] 1871. Indications point to a retardation of one and ahalf hours both before and since. But such discrepancy of resultproves nothing concerning a resisting medium, but rather is anargument against its existence. Besides, Faye's comet, in fourrevolutions of seven years each, shows no sign of retardation. The truth may be this, that a kind of atmosphere exists around thesun, perhaps revealed by the zodiacal light, that reaches beyondwhere Encke's comet dips inside the orbit of Mercury, and thusretards this body, but does not reach beyond the orbit of Mars, where Faye's comet wheels and withdraws. _Of what do Comets consist?_ The unsolved problems pertaining to comets are very numerous andexceedingly delicate. Whence come they? Why did they not contract tocentres of nebulæ? Are there regions where attractions are balanced, and matter is left to contract on itself, till the movements ofsuns and planets adds or diminishes attractive force on one side, and so allows them to be drawn slowly toward one planet, and itssun, or another? There is ground for thinking that the comet of1866 and its train of meteors, visible to us in November, was thusdrawn into our system by the planet Uranus. Indeed, Leverrier hasconjecturally fixed upon the date of A. D. 128 as the time when itoccurred; but another and closer observation of its next return, in 1899, will be needed to give confirmation to the opinion. Oursun's authority extends at least half-way to the nearest fixed star, one hundred thousand times farther than the orbit of the earth. Meteoric and cometary matter lying [Page 132] there, in a sphericalshell about the solar system, balanced between the attraction ofdifferent suns, finally feels the power that determines its destinytoward our sun. It would take 167, 000, 000 years to come thence toour system. The conditions of matter with which we are acquainted do not coverall the ground presented by these mysterious visitors. We knowa gas sixteen times as light as air, but hydrogen is vastly tooheavy and dense; for we see the faintest star through thousands ofmiles of cometary matter; we know that water may become cloudy vapor, but a little of it obscures the vision. Into what more ethereal, and we might almost say spiritual, forms matter may be changed wecannot tell. But if we conceive comets to be only gas, it wouldexpand indefinitely in the realms of space, where there is no forceof compression but its own. We might say that comets are composedof small separate masses of matter, hundreds of miles apart; and, looking through thousands of miles of them, we see light enoughreflected from them all to seem continuous. Doubtless that is sometimesthe case. But the spectroscope shows another state of things: itreveals in some of these comets an incandescent gas--usually someof the combinations of carbon. The conclusion, then, naturally isthat there are both gas and small masses of matter, each with anorbit of its own nearly parallel to those of all the others, andthat they afford some attraction to hold the mass of intermingled andconfluent gas together. Our best judgment, then, is that the nucleusis composed of separate bodies, or matter in a liquid condition, capable of being vaporized by the heat of the sun, and driven off, [Page 133] as steam from a locomotive, into a tail. Indications ofthis are found in the fact that tails grow smaller at successivereturns, as the matter capable of such vaporization becomescondensed. In some instances, as in that of the comet of 1843, thehead was diminished by the manufacture of a tail. On the other hand, Professor Peirce showed that the nucleus of the comets of 1680, 1843, and 1858 must have had a tenacity equal to steel, to preventbeing pulled apart by the tidal forces caused by its terribleperihelion sweep around the sun. It is likely that there are great varieties of condition in differentcomets, and in the same comet at times. We see them but a few daysout of the possible millions of their periodic time; we see themonly close to the sun, under the spur of its tremendous attractionand terrible heat. This gives us ample knowledge of the path oftheir orbit and time of their revolution, but little ground forjudgment of their condition, when they slowly round the uttermostcape of their far-voyaging, in the terrible cold and darkness, to commence their homeward flight. The unsolved problems are notall in the distant sun and more distant stars, but one of themis carried by us, sometimes near, sometimes far off; but ouracquaintance with the possible forms and conditions of matter istoo limited to enable us to master the difficulties. _Will Comets strike the Earth?_ Very likely, since one or two have done so within a recent period. What will be the effect? That depends on circumstances. There isgood reason to suppose we passed through the tail of a comet in1861, and the only [Page 134] observable effect was a peculiarphosphorescent mist. If the comet were composed of small meteoricmasses a brilliant shower would be the result. But if we fairlyencountered a nucleus of any considerable mass and solidity, theresult would be far more serious. The mass of Donati's comet hasbeen estimated by M. Faye to be 1/20000 of that of the earth. Ifthis amount of matter were dense as water, it would make a globefive hundred miles in diameter; and if as dense as Professor Peirceproved the nucleus of this comet to be, its impact with the earthwould develop heat enough to melt and vaporize the hardest rocks. Happily there is little fear of this: as Professor Newcomb says, "Sosmall is the earth in comparison with celestial space, that if onewere to shut his eyes and fire at random in the air, the chance ofbringing down a bird would be better than that of a comet of anykind striking the earth. " Besides, we are not living under agovernment of chance, but under that of an Almighty Father, whoupholdeth all things by the word of his power; and no world can cometo ruin till he sees that it is best. [Page 135]VIII. THE PLANETS AS INDIVIDUALS. "Through faith we understand that the worlds [plural] were framedby the word of God, so that things which were seen were not madeof things which do appear. "--_Heb. _ xi. 3. [Page 136]"O rich and various man! Thou palace of sight and sound, carryingin thy senses the morning, and the night, and the unfathomablegalaxy; in thy brain the geometry of the city of God; in thy heartthe power of love, and the realms of right and wrong. An individualman is a fruit which it costs all the foregoing ages to form andripen. He is strong, not to do but to live; not in his arms, butin his heart; not as an agent, but as a fact. "--EMERSON. [Page 137]VII. _THE PLANETS AS INDIVIDUALS. _ How many bodies there may be revolving about the sun we have nomeans to determine or arithmetic to express. When the new starof the American Republic appeared, there were but six planetsdiscovered. Since then three regions of the solar system have beenexplored with wonderful success. The outlying realms beyond Saturnyielded the planet Uranus in 1781, and Neptune in 1846. The middleregion between Jupiter and Mars yielded the little planetoid Ceresin 1801, Pallas in 1802, and one hundred and ninety others since. The inner region between Mercury and the sun is of necessity fullof small meteoric bodies; the question is, are there any bodieslarge enough to be seen? The same great genius of Leverrier that gave us Neptune from theobserved perturbations of Uranus, pointed out perturbations inMercury that necessitated either a planet or a group of planetoidsbetween Mercury and the sun. Theoretical astronomers, aided by thefact that no planet had certainly been seen, and that all asserteddiscoveries of one had been by inexperienced observers, inclinedto the belief in a group, or that the disturbance was caused bythe matter reflecting the zodiacal light. When the total eclipse of the sun occurred in 1878, [Page 138]astronomers were determined that the question of the existence of anintra-mercurial planet should be settled. Maps of all the stars inthe region of the sun were carefully studied, sections of the skyabout the sun were assigned to different observers, who shouldattend to nothing but to look for a possible planet. It is nowconceded that Professor Watson, of Ann Arbor, actually saw thesought-for body. VULCAN. The god of fire; its sign [Symbol], his hammer. DISTANCE FROM THE SUN, 13, 000, 000 MILES. ORBITAL REVOLUTION, ABOUT20 DAYS. MERCURY. The swift messenger of the gods; sign [Symbol], his caduceus. DISTANCE FROM THE SUN, 35, 750, 000 MILES. DIAMETER, 2992 MILES. ORBITAL REVOLUTION, 87. 97 DAYS. ORBITAL VELOCITY, 1773 MILES PERMINUTE. AXIAL REVOLUTION, 24H. 5M. Mercury shines with a white light nearly as bright as Sirius; isalways near the horizon. When nearly between us and the sun, asat D (Fig. 46, p. 113), its illuminated side nearly opposite tous, we, looking from E, see only a thin crescent of its light. When it is at its greatest angular distance from the sun, as A orC, we see it illuminated like the half-moon. When it is beyond thesun, as at E, we see its whole illuminated face like the full-moon. The variation of its apparent size from the varying distance isvery striking. At its extreme distance from the earth it subtendsan angle of only five seconds; nearest to us, an angle of twelveseconds. Its distance from the earth varies nearly as one to three, and its apparent size in the inverse ratio. [Page 139]When Mercury comes between the earth and the sun, near the linewhere the planes of their orbits cut each other by reason of theirinclination, the dark body of Mercury will be seen on the brightsurface of the sun. This is called a transit. If it goes acrossthe centre of the sun it may consume eight hours. It goes 100, 000miles an hour, and has 860, 000 miles of disk to cross. The transit of1818 occupied seven and a half hours. The transits for the remainderof the century will occur: November 7th 1881 | November 10th 1894 May 9th 1891 | November 4th 1901 VENUS. Goddess of beauty; its sign [Symbol], a mirror. DISTANCE FROM THE SUN, 66, 750, 000 MILES. DIAMETER, 7660 MILES. ORBITAL VELOCITY, 1296 MILES PER MINUTE. AXIAL REVOLUTION, 23H. 21M. ORBITAL REVOLUTION, 224. 7 DAYS. This brilliant planet is often visible in the daytime. I was oncedelighted by seeing Venus looking down, a little after mid-daythrough the open space in the dome of the Pantheon at Rome. Ithas never since seemed to me as if the home of all the gods wasdeserted. Phoebus, Diana, Venus and the rest, thronged throughthat open upper door at noon of night or day. Arago relates thatBonaparte, upon repairing to Luxemburg when the Directory was aboutto give him a _fête_, was much surprised at seeing the multitudepaying more attention to the heavens above the palace than to himor his brilliant staff. Upon inquiry, he learned that these curiouspersons were observing with astonishment a star which they supposedto be that of the conqueror of Italy. The emperor himself was notindifferent when [Page 140] his piercing eye caught the clear lustreof Venus smiling upon him at mid-day. This unusual brightness occurs when Venus is about five weeks beforeor after her inferior conjunction, and also nearest overhead bybeing north of the sun. This last circumstance occurs once in eightyears, and came on February 16th, 1878. Venus may be as near the earth as 22, 000, 000 miles, and as faraway as 160, 000, 000. This variation of its distances from the earthis obviously much greater than that of Mercury, and its consequentapparent size much more changeable. Its greatest and least apparentsizes are as ten and sixty-five (Fig. 53). [Illustration: Fig. 53. --Phases of Venus, and Varions ApparentDimensions. ] When Copernicus announced the true theory of the solar system, hesaid that if the inferior planets could be clearly seen they wouldshow phases like the moon. When Galileo turned the little telescopehe had made on Venus, he confirmed the prophecy of Copernicus. Desiring to take time for more extended observation, and still beable to assert the priority of his discovery, he published thefollowing anagram, in which his discovery was contained: [Page 141] "Hæc immatura a me jam frustra leguntur o. Y. " (These unripe things are now vainly gathered by me. ) He first saw Venus as gibbous; a few months revealed it as crescent, and then he transposed his anagram into: "Cynthiæ figuras æmulatur mater amorum. " (The mother of loves imitates the phases of Cynthia. ) Many things that were once supposed to be known concerning Venus arenot confirmed by later and better observations. Venus is surroundedby an atmosphere so dense with clouds that it is conceded thather time of rotation and the inclination of her axis cannot bedetermined. She revealed one of the grandest secrets of the universeto the first seeker; showed her highest beauty to her first ardentlover, and has veiled herself from the prying eyes of later comers. Florence has built a kind of shrine for the telescope of Galileo. By it he discovered the phases of Venus, the spots on the sun, the mountains of the moon, the satellites of Jupiter, and someirregularities of shape in Saturn, caused by its rings. Galileosubsequently became blind, but he had used his eyes to the bestpurpose of any man in his generation. THE EARTH. Its sign [Symbol]. DISTANCE FROM THE SUN, 92, 500, 000 MILES. DIAMETER, POLAR, 7899MILES; EQUATORIAL, 7925-1/2 MILES. AXIAL REVOLUTION, 23H. 56M. 4. 09S. ; ORBITAL, 365. 86. ORBITAL VELOCITY PER MINUTE, 1152. 8 MILES. Let us lift ourselves up a thousand miles from the earth. We see itas a ball hung upon nothing in empty space. As the drop of fallingwater gathers itself [Page 142] into a sphere by its own inherentattraction, so the earth gathers itself into a ball. Noticingclosely, we see forms of continents outlined in bright relief, andoceanic forms in darker surfaces. We see that its axis of revolutionis nearly perpendicular to the line of light from the sun. One-halfis always dark. The sunrise greets a new thousand miles every hour;the glories of [Page 143] the sunset follow over an equal space, 180° behind. We are glad that the darkness never overtakes themorning. [Illustration: Fig. 54. --Earth and Moon in Space. ] _The Aurora Borealis. _ While east and west are gorgeous with sunrise and sunset, the northis often more glorious with its aurora borealis. We remember thatall worlds have weird and inexplicable appendages. They are notlimited to their solid surfaces or their circumambient air. Thesun has its fiery flames, corona, zodiacal light, and perhaps afiner kind of atmosphere than we know. The earth is[Page 144]not without its inexplicable surroundings. It has not only itsgorgeous eastern sunrise, its glorious western sunset, high aboveits surface in the clouds, but it also has its more glorious northerndawn far above its clouds and air. The realm of this royal splendoris as yet an unconquered world waiting for its Alexander. There arecertain observable facts, viz. , it prevails mostly near the arcticcircle rather than the pole; it takes on various forms--cloud-like, arched, straight; it streams like banners, waves like curtains inthe wind, is inconstant; is either the cause or result of electricdisturbance; it is often from four hundred to six hundred milesabove the earth, while our air cannot be over one hundred miles. It almost seems like a revelation to human eyes of those vast, changeable, panoramic pictures by which the inhabitants of heavenare taught. [Illustration: Fig. 55. --The Aurora as Waving Curtains. ] Investigation has discovered far more mysteries than it has explained. It is possible that the same cause that produces sun-spots producesaurora in all space, visible in all worlds. If so, we shall seemore abundant auroras at the next maximum of sun-spot, between1880-84. _The Delicate Balance of Forces. _ A soap-bubble in the wind could hardly be more flexible in formand sensitive to influence than is the earth. On the morning ofMay 9th, 1876, the earth's crust at Peru gave a few great throbsupward, by the action of expansive gases within. The sea fled, and returned in great waves as the land rose and fell. Then thesewaves fled away over the great mobile surface, and in less thanfive hours they had covered a space equal to half of Europe. Thewaves ran out to the Sandwich Islands, six [Page 145] thousandmiles, at the rate of five hundred miles an hour, and arrived therethirty feet high. They not only sped on in straight radial lines, but, having run up the coast to California, were deflected away intothe former series of waves, making the most complex undulations. Similar beats of the great heart of the earth have sent its pulsesas widely and rapidly on previous occasions. The figure of the earth, even on the ocean, is irregular, in consequenceof the greater preponderance of land--and hence greater density--in thenorthern hemisphere. These irregularities are often very perplexingin making exact geodetic measurements. The tendency of matter tofly from the centre by reason of revolution causes the equatorialdiameter to be twenty-six, miles longer than the polar one. By thisforce the Mississippi River is enabled to run up a hill nearlythree miles high at a very rapid rate. Its mouth is that distancefarther from the centre of the earth than its source, when butfor this rotation both points would be equally distant. If the water became more dense, or if the world were to revolvefaster, the oceans would rush to the equator, burying the tallestmountains and leaving polar regions bare. If the water should becomelighter in an infinitesimal degree, or the world rotate more slowly, the poles would be submerged and the equator become an arid waste. No balance, turning to 1/1000 of a grain, is more delicate thanthe poise of forces on the world. Laplace has given us proof thatthe period of the earth's axial rotation has not changed 1/100of a second of time in two thousand years. [Page 146]_Tides. _ But there is an outside influence that is constantly acting uponthe earth, and to which it constantly responds. Two hundred andforty thousand miles from the earth is the moon, having 1/81 themass of the world. Its attractive influence on the earth causes themovable and nearer portions to hurry away from the more stable anddistant, and heap themselves up on that part of the earth nearestthe moon. Gravitation is inversely as the square of the distance;hence the water on the surface of the earth is attracted more thanthe body of the earth, some parts of which are eight thousand milesfarther off; hence the water rises on the side next the moon. Butthe earth, as a whole, is nearer the moon than the water on theopposite side, and being drawn more strongly, is taken away fromthe water, leaving it heaped up also on the side opposite to themoon. A subsidiary cause of tides is found in the revolution of the earthand moon about their common centre of gravity. Revolution aboutan axis through the centre of a sphere enlarges the equator bycentrifugal force. Revolution about an axis touching the surfaceof a flexible globe converts it into an egg-shaped body, with thelonger axis perpendicular to the axis of revolution. In Fig. 56 thepoint of revolution is seen at the centre of gravity at G; hence, in the revolution of earth and moon as one, a strong centrifugalforce is caused at D, and a less one at C. This gives greater heightto the tides than the attraction of the moon alone could produce. [Page 147][Illustration: Fig. 56. ] If the earth had no axial revolution, the attractive point wherethe tide rises would be carried around the earth once in twenty-sevendays by the moon's revolution about the earth. But since the earthrevolves on its axis, it presents a new section to the moon's attractionevery hour. If the moon were stationary, that would bring two hightides in exactly twenty-four hours; but as the moon goes forward, we need nearly twenty-five hours for two tides. The attractive influence of the sun also gives us a tide four-tenthsas great as that of the moon. When these two influences of the sunand moon combine, as they do, in conjunction--when both bodiesare on one side of the earth; or in opposition, sun and moon beingon opposite sides of the earth--we have spring or increased tides. When the moon is in its first or third quarter, _i. E. _, when aline from the moon to the earth makes a right angle with one fromthe sun to the earth, these influences antagonize one another, and we have the neap or low tides. It is easy to see that if, when the moon was drawing its usualtide, the sun drew four-tenths of the water in a tide at rightangles with it, the moon's tide must be by so much lower. Becauseof the inertia of the water [Page 148] it does not yield instantlyto the moon's influence, and the crest of the tide is some hoursbehind the advancing moon. The amount of tide in various places is affected by almost innumerableinfluences, as distance of moon at its apogee or perigee; its positionnorth, south, or at the equator; distance of earth from sun atperihelion and aphelion; the position of islands; the trend ofcontinents, etc. All eastern shores have far greater tides thanwestern. As the earth rolls to the east it leaves the tide-crestunder the moon to impinge on eastern shores, hence the tides offrom seventy-five to one hundred feet in the Bay of Fundy. Lakes andmost seas are too small to have perceptible tides. The spring-tidesin the Mediterranean Sea are only about three inches. This constant ebb and flow of the great sea is a grand provision forits purification. Even the wind is sent to the sea to be cleansed. The sea washes every shore, purifies every cove, bay, and rivertwice every twenty-four hours. All putrescible matter liable tobreed a pestilence is carried far from shore and sunk under fathomsof the never-stagnant sea. The distant moon lends its mighty powerto carry the burdens of commerce. She takes all the loads thatcan be floated on her flowing tides, and cheerfully carries themin opposite directions in successive journeys. It must be conceded that the profoundest study has not masteredthe whole philosophy of tides. There are certain facts which areapparent, but for an explanation of their true theory such men asLaplace, Newton, and Airy have labored in vain. There are plentyof other worlds still to conquer. [Page 150][Illustration: Fig. 57. --Lunar Day. ] [Page 151]THE MOON. New moon, [Symbol]; first quarter, [Symbol]; full moon, [Symbol];last quarter, [Symbol]. EXTREME DISTANCE FROM THE EARTH, 259, 600 MILES; LEAST, 221, 000MILES; MEAN, 240, 000 MILES. DIAMETER, 2164. 6 MILES [2153, LOCKYER]. REVOLUTION ABOUT THE EARTH, 29-1/2 DAYS. AXIAL REVOLUTION, SAMETIME. When the astronomer Herschel was observing the southern sky fromthe Cape of Good Hope, the most clever hoax was perpetrated thatever was palmed upon a credulous public. Some new and wonderfulinstruments were carefully described as having been used by thatastronomer, whereby he was enabled to bring the moon so close thathe could see thereon trees, houses, animals, and men-like humanbeings. He could even discern their movements, and gestures thatindicated a peaceful race. The extent of the hoax will be perceivedwhen it is stated that no telescope that we are now able to makereveals the moon more clearly than it would appear to the nakedeye if it was one hundred or one hundred and fifty miles away. The distance at which a man can be seen by the unaided eye variesaccording to circumstances of position, background, light, andeye, but it is much inside of five miles. Since, however, the moon is our nearest neighbor, a member of ourown family in fact, it is a most interesting object of study. A glance at its familiar face reveals its unequal illumination. All ages and races have seen a man in the moon. All lovers havesworn by its constancy, and only part of them have kept their oaths. Every twenty-nine or thirty days we see a silver crescent in thewest, and are glad if it comes over the right shoulder--so [Page152] much tribute does habit pay to superstition. The next night itis thirteen degrees farther east from the sun. We note the stars itoccults, or passes by, and leaves behind as it broadens its disk, till it rises full-orbed in the east when the sun sinks in the west. It is easy to see that the moon goes around the earth from west toeast. Afterward it rises later and smaller each night, till atlength, lost from sight, it rises about the same time as the sun, and soon becomes the welcome crescent new moon again. The same peculiarities are always evident in the visible face ofthe moon; hence we know that it always presents the same side tothe earth. Obviously it must make just one axial to one orbitalrevolution. Hold any body before you at arm's-length, revolve itone-quarter around you until exactly overhead. If it has not revolvedon an axis between the hands, another quarter of the surface isvisible; but if in going up it is turned a quarter over, by thehands holding it steady, the same side is visible. Three causesenable us to see a little more than half the moon's surface: 1. Thespeed with which it traverses the ellipse of its orbit is variable. It sometimes gets ahead of us, sometimes behind, and we see fartheraround the front or back part. 2. The axis is a little inclined tothe plane of its orbit, and its orbit a little inclined to ours;hence we see a little over its north pole, and then again overthe south pole. 3. The earth being larger, its inhabitants seea little more than half-way around a smaller body. These causescombined enable us to see 576/1000 of the moon's surface. Our eyeswill never see the other side of the moon. If, now, being solid, her axial revolution could [Page 153] be increased enough to makeone more revolution in two or three years, that difference betweenher axial and orbital revolution would give the future inhabitantsof the earth a view of the entire circumference of the moon. Yet ifthe moon were once in a fluid state, or had oceans on the surface, the enormous tide caused by the earth would produce friction enough, as they moved over the surface, to gradually retard the axialrevolution till the two tidal elevations remained fixed toward andopposite the earth, and then the axial and orbital revolutions wouldcorrespond, as at present. In fact, we can prove that the form ofthe moon is protuberant toward the earth. Its centre of gravity isthirty-three miles beyond its centre of magnitude, which is the samein effect as if a mountain of that enormous height rose on the earthside. Hence any fluid, as water or air, would flow round to theother side. The moon's day, caused by the sun's light, is 29-1/2 times as longas ours. The sun shines unintermittingly for fifteen days, raising atemperature as fervid as boiling water. Then darkness and frightfulcold for the same time succeed, except on that half where the earthacts as a moon. The earth presents the same phases--crescent, full, and gibbous--to the moon as the moon does to us, and for the samecauses. Lord Rosse has been enabled, by his six-foot reflector, tomeasure the difference of heat on the moon under the full blazeof its noonday and midnight. He finds it to be no less than fivehundred degrees. People not enjoying extremes of temperature shouldshun a lunar residence. The moon gives us only 1/6180000 as muchlight as the sun. A sky full of moons would scarcely make daylight. [Page 154][Illustration: Fig. 58. --View of the Moon near the Third Quarter. From a Photograph by Professor Henry Draper. ] There are no indications of air or water on the moon. When it occultsa star it instantly shuts off the light and as instantly revealsit again. An atmosphere would gradually diminish and reveal thelight, and by refraction [Page 155] cause the star to be hidden inmuch less time than the solid body of the moon would need to passover it. If the moon ever had air and water, as it probably did, they are now absorbed in the porous lava of its substance. _Telescopic Appearance. _ [Illustration: Fig. 59. --Illumination of Craters and Peaks. ] Probably no one ever saw the moon by means of a good telescopewithout a feeling of admiration and awe. Except at full-moon, wecan see where the daylight struggles with the dark along the lineof the moon's sunrise or sunset. This line is called the terminator. It is broken in the extreme, because the surface is as rough aspossible. In consequence of the small gravitation of the moon, utterabsence of the expansive power of ice shivering the cliffs, or thelevelling power of rains, precipices can stand in perpendicularity, mountains shoot up like needles, and cavities three miles deepremain unfilled. The light of the sun falling on the rough bodyof the moon, shown in section (Fig. 59), illuminates the wholecavity at _a_, part of the one at _b_, casts a long shadow from themountain at _c_, and touches the tip of the one at _d_, which appearsto a distant observer as a point of light beyond the terminator, As the moon revolves the conical cavity, _a_ is illuminated onthe forward side only; the light creeps down the backward sideof cavity _b_ to the bottom; mountain _c_. Comes directly underthe sun and casts no shadow, and mountain _d_ casts its long shadowover the plain. Knowing the time of revolution, and observing thechange of [Page 156] illumination, we can easily measure the heightof mountain and depth of crater. An apple, with excavations andadded prominences, revolved on its axis toward the light of acandle, admirably illustrates the crescent light that fills eitherside of the cavities and the shadows of the mountains on the plain. Notice in Fig. 58 the crescent forms to the right, showing cavitiesin abundance. [Illustration: Fig. 60. --Lunar Crater "Copernicus, " after Secchi. ] The selenography of one side of the moon is much better known tous than the geography of the earth. Our maps of the moon are farmore perfect than those of the earth; and the photographs of lunarobjects by Messrs. Draper and De la Rue are wonderfully perfect, [Page 157] and the drawings of Padre Secchi equally so (Fig. 60). The least change recognizable from the earth must be speedilydetected. There are frequently reports of discoveries of volcanoeson the moon, but they prove to be illusions. The moon will probablylook the same to observers a thousand years hence as it does to-day. This little orb, that is only 1/81 of the mass of the earth, hastwenty-eight mountains that are higher than Mont Blanc, that "monarchof mountains, " in Europe. _Eclipses. _ [Illustration: Fig. 61. --Eclipses; Shadows of Earth and Moon. ] It is evident that if the plane of the moon's orbit were to correspondwith that of the earth, as they all lie in the plane of the page(Fig. 61), the moon must pass between the centres of the earthand sun, and exactly behind the earth at every revolution. Suchsuccessive and total darkenings would greatly derange all affairsdependent on light. It is easily avoided. Venus does [Page 158] notcross the disk of the sun at every revolution, because of theinclination of the plane of its orbit to that of the earth (see Fig. 41, p. 107). So the plane of the orbit of the moon is inclined tothe orbit of the earth 5° 8' 39"; hence the full-moon is often aboveor below the earth's shadow, and the earth is below or above themoon's shadow at new moon. It is as if the moon's orbit were pulledup one-quarter of an inch from the page behind the earth, anddepressed as much below it between the earth and the sun. The pointwhere the orbit of the moon penetrates the plane of the ecliptic iscalled a node. If a new moon occur when the line of intersection ofthe planes of orbits points to the sun, the sun must be eclipsed; ifthe full-moon occur, the moon must be eclipsed. In any otherposition the sun or moon will only be partially hidden, or noeclipse will occur. If the new moon be near the earth it will completely obscure thesun. A dime covers it if held close to the eye. It may be so farfrom the earth as to only partially hide the sun; and, if it coverthe centre, leave a ring of sunlight on every side. This is calledan annular eclipse. Two such eclipses will occur this year (1879). If the full-moon passes near the earth, or is at perigee, it findsthe cone of shadow cast by the earth larger, and hence the eclipseis greater; if it is far from the earth, or near apogee, the earth'sshadow is smaller, and the eclipse less, or is escaped altogether. There is a certain periodicity in eclipses. Whenever the sun, moon, and earth are in a line, as in the total eclipse of July 29th, 1878, they will be in the same position after the earth has madeabout eighteen revolutions, [Page 159] and the moon two hundred andsixteen--that is, eighteen years after. This period, however, isdisregarded by astronomers, and each eclipse calculated by itself tothe accuracy of a second. How terrible is the fear of ignorance and superstition when the sunor moon appear to be in the process of destruction! how delightfulare the joys of knowledge when its prophesies in regard to theheavenly bodies are being fulfilled! MARS. The god or war; Its sign [Symbol], spear and shield. MEAN DISTANCE FROM THE SUN, 141, 000, 000 MILES. DIAMETER, 4211 MILES. REVOLUTION, AXIAL, 24H. 37M. 22. 7S. ; ORBITAL, 686. 98 DAYS. VELOCITYPER MINUTE, 899 MILES. SATELLITES, TWO. [Illustration: Fig. 62. --Apparent Size of Mars at Mean and ExtremeDistances. ] At intervals, on an average of two years one month and nineteendays, we find rising, as the sun goes down, the reddest star inthe heavens. Its brightness is exceedingly variable; sometimesit scintillates, and sometimes it shines with a steady light. Itsmarked peculiarities demand a close study. We find it to be Mars, the fiery god of war. Its orbit is far from circular. At perihelionit is 128, 000, 000 miles from the sun, and at aphelion 154, 000, 000;hence its mean distance is about 141, 000, 000. So great a changein its distance from the sun easily accounts for the change inits brilliancy. Now, if Mars and the earth revolved in circularorbits, the one 141, 000, 000 miles from the sun, and the other92, 000, 000, they would approach at conjunction within 49, 000, 000miles of each other, and at opposition be 233, 000, 000 miles apart. But Mars at perihelion may be only 128, 000, 000 miles from the sun, and earth at [Page 160] aphelion may be 94, 000, 000 miles from thesun. They are, then, but 34, 000, 000 miles apart. This favorableopportunity occurs about once in seventy-nine years. At its lastoccurrence, in 1877, Mars introduced to us his two satellites, thathad never before been seen by man. In consequence of this greatlyvarying distance, the apparent size of Mars differs very much (Fig. 62). Take a favorable time when the planet is near, also as nearoverhead as it ever comes, so as to have as little atmosphere aspossible to penetrate, and study the planet. The first thing thatstrikes the observer is a dazzling spot of white near the pole whichhappens to be toward him, or at both poles when the planet is sosituated that they can be seen. When the north pole is turned towardthe sun the size of the spot sensibly diminishes, and the spot atthe south pole enlarges, and _vice versa_. Clearly they areice-fields. Hence Mars has water, and air to carry it, and heat tomelt ice. It is winter at the south pole when Mars is farthest fromthe sun; therefore the ice-fields are larger than at the north pole. It is summer at the south pole when Mars is nearest the sun. Henceits ice-fields grow smaller [Page 161] than those of the north polein its summer. This carrying of water from pole to pole, and meltingof ice over such large areas, might give rise to uncomfortablecurrents in ocean and air; but very likely an inhabitant of earthmight be transported to the surface of Mars, and be no moresurprised at what he observed there than if he went to some point ofthe earth to him unknown. Day and night would be nearly of the samelength; winter would linger longer in the lap of spring; summerwould be one hundred and eighty-one days long; but as the seas aremore intermingled with the land, and the divisions of land have lessof continental magnitude, it may be conjectured that Mars might be acomfortable place of residence to beings like men. Perhaps thegreatest surprise to the earthly visitor would be to find himselfweighing only four-tenths as much as usual, able to leap twice ashigh, and lift considerable bowlders. _Satellites of Mars. _ The night of August 11th, 1877, is famous in modern astronomy. Mars has been a special object of study in all ages; but on thatevening Professor Hall, of Washington, discovered a satellite ofMars. On the 16th it was seen again, and its orbital motion followed. On the following night it was hidden behind the body of the planetwhen the observation began, but at the calculated time--at fouro'clock in the morning--it emerged, and established its character asa true moon, and not a fixed star or asteroid. Blessings, however, never come singly, for another object soon emerged which provedto be an inner satellite. This is extraordinarily near [Page 162]the planet--only four thousand miles from the surface--and itsrevolution is exceedingly rapid. The shortest period hitherto knownis that of the inner satellite of Saturn, 22h. 37m. The innersatellite of Mars makes its revolution in 7h. 39m. --a rapidity somuch surpassing the axial revolution of the planet itself, that itrises in the west and sets in the east, showing all phases of ourmoon in one night. The outer satellite is 12, 579 miles from Mars, and makes its revolution in 30h. 18m. Its diameter is six and aquarter miles; that of the inner one is seven and a half miles. Thiscan be estimated only by the amount of light given. ASTEROIDS. ALREADY DISCOVERED (1879), 192. DISTANCES FROM THE SUN, FROM 200, 000, 000TO 315, 000, 000 MILES. DIAMETERS, FROM 20 TO 400 MILES. MASS OF ALL, LESS THAN ONE-QUARTER OF THE EARTH. The sense of infinite variety among the countless number of celestialorbs has been growing rapidly upon us for half a century, and doubtlesswill grow much more in half a century to come. Just as we pausedin the consideration of planets to consider meteors and comets, at first thought so different, so must we now pause to consider aring of bodies, some of which are as small in comparison to Jupiter, the next planet, as aerolites are compared to the earth. In 1800 an association of astronomers, suspecting that a planetmight be found in the great distance between Mars and Jupiter, divided the zodiac into twenty-four parts, and assigned one part toeach astronomer for a thorough search; but, before their organizationcould commence work, Piazzi, an Italian astronomer of Palermo, [Page163] found in Taurus a star behaving like a planet. In six weeks itwas lost in the rays of the sun. It was rediscovered on itsemergence, and named Ceres. In March, 1802, a second planet wasdiscovered by Olbers in the same gap between Mars and Jupiter, andnamed Pallas. Here was an embarrassment of richness. Olberssuggested that an original planet had exploded, and that more piecescould be found. More were found, but the theory is exploded intomore pieces than a planet could possibly be. Up to 1879 one hundredand ninety-two have been discovered, with a prospect of more. Between 1871-75 forty-five were discovered, showing that they aresought for with great skill. In the discovery of these bodies, ourAmerican astronomers, Professors Watson and Peters, are withoutpeers. Between Mars and Jupiter is a distance of some 339, 000, 000 miles. Subtract 35, 000, 000 miles next to Mars and 50, 000, 000 miles nextto Jupiter, and there is left a zone 254, 000, 000 miles wide outsideof which the asteroids never wander. If any ever did, the attractionof Mars or Jupiter may have prevented their return. Since the orbits of Mars and Jupiter show no sign of being affectedby these bodies for a century past, it is probable that their numberis limited, or at least that their combined mass does not approximatethe size of a planet. Professor Newcomb estimates that if all thatare now discovered were put into one planet, it would not be overfour hundred miles in diameter; and if a thousand more should exist, of the average size of those discovered since 1850, their additionwould not increase the diameter to more than five hundred miles. [Page 164]That all these bodies, which differ from each other in no respectexcept in brilliancy, can be noted and fixed so as not to be mistakenone for another, and instantly recognized though not seen for adozen years, is one of the highest exemplifications of the accuracyof astronomical observation. JUPITER. The king of the gods; sign [Symbol], the bird of Jove. DISTANCE FROM THE SUN, PERIHELION, 457, 000, 000 MILES; APHELION, 503, 000, 000 MILES. DIAMETER, EQUATORIAL, 87, 500 MILES; POLAR, 82, 500MILES. VOLUME, 1300 EARTHS. MASS, 213 EARTHS. AXIAL REVOLUTION, 9H. 55M 20S. ORBITAL REVOLUTION, 11 YEARS 317 DAYS. VELOCITY, 483. 6MILES PER MINUTE. [Illustration: Fig. 63. --Jupiter as seen by the great WashingtonTelescope. Drawn by Mr. Holden. ] Jupiter rightly wears the name of the "giant planet. " His orbitis more nearly circular than most smaller planets. He could notturn short corners with facility. We know little of his surface. His spots and belts are [Page 165] changeable as clouds, which theyprobably are. Some spots may be slightly self-luminous, but not thepart of the planet we see. It is covered with an enormous depth ofatmosphere. Since the markings in the belts move about one hundredmiles a day, the Jovian tempests are probably not violent. It is, however, a singular and unaccountable fact, as remarked by Arago, that its trade-winds move in an opposite direction from ours. Jupiter receives only one twenty-seventh as much light and heat fromthe sun as the earth receives. Its lighter density, being about thatof water, indicates that it still has internal heat of its own. Indeed, it is likely that this planet has not yet cooled so as tohave any solid crust, and if its dense vapors could be deposited onthe surface, its appearance might be more suggestive of the sun thanof the earth. _Satellites of Jupiter. _ In one respect Jupiter seems like a minor sun--he is royally attendedby a group of planets: we call them moons. This system is a favoriteobject of study to everyone possessing a telescope. Indeed, I haveknown a man who could see these moons with the naked eye, and givetheir various positions without mistake. Galileo first revealedthem to ordinary men. We see their orbits so nearly on the edgethat the moons seem to be sliding back and forth across and behindthe disk, and to varying distances on either side. Fig. 64 is therepresentation of their appearance at successive observations inNovember, 1878. Their motion is so swift, and the means of comparisonby one another and the planet so excellent, that they can be seento change their places, [Page 166] be occulted, emerge from shadow, and eclipse the planet, in an hour's watching. [Illustration: Fig. 64. --_a. _ Various Positions of Jupiter's Moons;_b. _ Greatest Elongation of each Satellite. ] ELEMENTS OF JUPITER'S SATELLITES. +-------------------------------------------------------------+ | | Mean Distance | | | | | from Jupiter. | Sidereal Period. | Diameter. | | |---------------+------------------+----------| | | Miles. | Days Hrs. Min. | Miles. | | I. Io | 260, 000 | 1 18 28 | 2, 352 | | II. Europa | 414, 000 | 3 13 43 | 2, 099 | | III. Ganymede | 661, 000 | 7 3 59 | 3, 436 | | IV. Callisto | 1, 162, 000 | 16 18 5 | 2, 929 | +-------------------------------------------------------------+ It is seen by the above table that all these moons are larger thanours, one larger than Mercury, and the asteroids are hardly largeenough to make respectable moons for them. They differ in color:I. And II. Have a bluish tinge; III. A yellow; and IV. Is red. The amount of light given by these satellites varies in the mostsudden and inexplicable manner. Perhaps it may be owing to thedifferent distributions of land and water on them. The mass of allof them is . 000171 of Jupiter. [Page 167]If the Jovian system were the only one in existence, it would bea surprising object of wonder and study. A monster planet, 85, 000miles in diameter, hung on nothing, revolving its equatorial surfaceforty-five miles a minute, holding four other worlds in steadyorbits, some of them at a speed of seven hundred miles a minute, and the whole system carried through space at five hundred milesa minute. Yet the discovery of all this display of power, skill, and stability is only reading the easiest syllables of the vastliterature of wisdom and power. SATURN. The god or time; sign [Symbol], his scythe. MEAN DISTANCE FROM THE SUN, 881, 000, 000 MILES. DIAMETER, POLAR, 66, 500 MILES; EQUATORIAL, 73, 300 MILES. AXIAL REVOLUTION, 10H. 14M. PERIODIC TIME, 29T YEARS. MOONS, EIGHT. The human mind has used Saturn and the two known planets beyondfor the last 200 years as a gymnasium. It has exercised itselfin comprehending their enormous distances in order to clear thosegreater spaces, to where the stars are set; it has exercised itsingenuity at interpreting appearances which signify something otherthan they seem, in order that it may no longer be deluded by anysunrises into a belief that the heavenly dome goes round the earth. That a wandering point of light should develop into such amazinggrandeurs under the telescope, is as unexpected as that every tinyseed should show peculiar markings and colors under the microscope. [Illustration: Fig. 65. --View of Saturn and his Rings. ] There are certain things that are easy to determine, such as size, density, periodic time, velocity, etc. ; but other things are exceedinglydifficult to determine. It requires long sight to read when thebook is held [Page 168] 800, 000, 000 miles away. Only very few, ifmore than two, opportunities have been found to determine the timeof Saturn's rotation. On the evening of December 7th, 1870, Professor Hall observed a brilliant white spot suddenly show itselfon the body of this planet. It was as if an eruption of white hotmatter burst up from the interior. It spread eastward, and remainedbright till January, when it faded. No such opportunity for gettinga basis on which to found a calculation of the time of the rotationof Saturn has occurred since Sir William Herschel's observations;and, very singularly, the two times deduced wonderfullycoincide--that of Herschel being 10h. 16m. , that of Mr. Hall being10h. 14m. [Page 169]The density of Saturn is less than that of water, and its velocityof rotation so great that centrifugal force antagonizes gravitationto such an extent that bodies weigh on it about the same as on theearth. All the fine fancies of the habitability of this vaporousworld, all the calculations of the number of people that couldlive on the square miles of the planet and its enormous rings, are only fancy. Nothing could live there with more brains than afish, at most. It is a world in formative processes. We cannot hearthe voice of the Creator there, but we can see matter responsiveto the voice, and moulded by his word. _Rings of Saturn. _ The eye and mind of man have worked out a problem of marvellousdifficulty in finding a true solution of the strange appearanceof the rings. Galileo has the immortal honor of first having seensomething peculiar about this planet. He wrote to the Duke of Tuscany, "When I view Saturn it seems _tricorps_. The central body seems thelargest. The two others, situated, the one on the east, and theother on the west, seem to touch it. They are like two supporters, who help old Saturn on his way, and always remain at his side. "Looking a few years later, the rings having turned from view, hesaid, "It is possible that some demon mocked me;" and he refusedto look any more. Huyghens, in March, 1655, solved the problem of the triform appearanceof Saturn. He saw them as handles on the two sides. In a year theyhad disappeared, and the planet was as round as it seemed to Galileoin 1612. He did not, however, despair; and in October, [Page 170]1656, he was rewarded by seeing them appear again. He wrote ofSaturn, "It is girdled by a thin plain ring, nowhere touching, inclined to the ecliptic. " Since that time discoveries have succeeded one another rapidly. "We have seen by degrees a ring evolved out of a triform planet, and the great division of the ring and the irregularities on itbrought to light. Enceladus, and coy Mimas, faintest of twinklers, are caught by Herschel's giant mirrors. And he, too, first of men, realizes the wonderful tenuity of the ring, along which he sawthose satellites travelling like pearls strung on a silver thread. Then Bond comes on the field, and furnishes evidence to show thatwe must multiply the number of separate rings we know not how manyfold. And here we reach the golden age of Saturnian discovery, when Bond, with the giant refractor of Cambridge, and Dawes, withhis 6-1/3-inch Munich glass, first beheld that wonderful darksemi-transparent ring, which still remains one of the wonders ofour system. But the end is not yet: on the southern surface ofthe ring, ere summer fades into autumn, Otto Struve in turn comesupon the field, detects, as Dawes had previously done, a divisioneven in the dark ring, and measures it, while it is invisible toLassell's mirror--a proof, if one were needed, of the enormoussuperiority possessed by refractors in such inquiries. Then weapproach 1861, when the ring plane again passes through the earth, and Struve and Wray observe curious nebulous appearances. "[*] [Footnote *: Lockyer. ] Our opportunities for seeing Saturn vary greatly. As the earth atone part of its orbit presents its south pole [Page 171] to the sun, then its equator, then the north pole, so Saturn; and we, in thedirection of the sun, see the south side of the rings inclined at anangle of 27°; next the edge of the rings, like a fine thread oflight; then the north side at a similar inclination. On February7th, 1878, Saturn was between Aquarius and Pisces, with the edge ofthe ring to the sun. In 1885, the planet being in Taurus, the southside of the rings will be seen at the greatest advantage. From 1881till 1885 all circumstances will combine to give most favorablestudies of Saturn. Meanwhile study the picture of it. The outer ringis narrow, dark, showing hints of another division, sometimes moreevident than at others, as if it were in a state of flux. The inner, or second, ring is much brighter, especially on the outer edge, andshading off to the dusky edge next to the planet. There is no signof division into a third dusky innermost ring, as was plainly seenby Bond. This, too, may be in a state of flux. The markings of the planet are delicate, difficult of detection, and are not like those stark zebra stripes that are so oftenrepresented. The distance between the planet and the second ring seems to bediminished one-half since 1657, and this ring has doubled its breadthin the same time. Some of this difference may be owing to our greatertelescopic power, enabling us to see the ring closer to the planet;but in all probability the ring is closing in upon the centralbody, and will touch it by A. D. 2150. Thus the whole ring mustultimately fall upon the planet, instead of making a satellite. We are anxious to learn the nature of such a ring. [Page 172]Laplace mathematically demonstrated that it cannot be uniform andsolid, and survive. Professor Peirce showed it could not be fluid, and continue. Then Professor Maxwell showed that it must be formedof clouds of satellites too small to be seen individually, and toonear together for the spaces to be discerned, unless, perhaps, wemay except the inner dark ring, where they are not near enough tomake it positively luminous. Indeed, there is some evidence that themeteoroids are far enough apart to make the ring partiallytransparent. We look forward to the opportunities for observation in 1882 withthe brightest hope that these difficult questions will be solved. _Satellites of Saturn. _ The first discovered satellite of Saturn seen by Huyghens was in1655, and the last by the Bonds, father and son, of Cambridge, in 1848. These are eight in number, and are named: Distant from Saturn's centre. I. Mimas 119, 725 miles. II. Enceladus 153, 630 " III. Tethys 190, 225 " IV. Dione 243, 670 " V. Rhea 340, 320 " VI. Titan 788, 915 " VII. Hyperion 954, 160 " VIII. Japetus 2, 292, 790 " Titan can be seen by almost any telescope; I. , II. , and III. , onlyby the most powerful instrument. All except Japetus revolve nearlyin the plane of the ring. Like the moons of Jupiter, they presentremarkable and unaccountable variations of brilliancy. An inspection[Page 173] of the table reveals either an expectation that anothermoon will be discovered between V. And VI. , and about three morebetween VII. And VIII. , or that these gaps may be filled with groupsof invisible asteroids, as the gap between Mars and Jupiter. Thiswill become more evident by drawing Saturn, the rings, and orbits ofthe moons all as circles, on a scale of 10, 000 miles to the inch. Saturn will be in the centre, 70, 000 miles in diameter; then a gap, decreasing twenty-nine miles a year to the first ring, of, say, 10, 000 miles; a dark ring 9000 miles wide; next the brightest ring18, 300 miles wide; then a gap of 1750 miles; then the outer ring10, 000 miles wide; then the orbits of the satellites in order. If the scenery of Jupiter is magnificent, that of Saturn must besublime. If one could exist there, he might wander from the illuminatedside of the rings, under their magnificent arches, to the darkenedside, see the swift whirling moons; one of them presenting ten timesthe disk of the earth's moon, and so very near as to enable himto watch the advancing line of light that marks the lunar morningjourneying round that orb. URANUS. Sign [Symbol]; the initial of Herschel, and sign of the world. DISTANCE FROM THE SUN, 1, 771, 000, 000 MILES. DIAMETER, 31, 700 MILES. AXIAL REVOLUTION UNKNOWN. ORBITAL, 84 YEARS. VELOCITY PER MINUTE, 252 MILES. MOONS, FOUR. Uranus was presented to the knowledge of man as an unexpected rewardfor honest work. It was first mistaken by its discoverer for a comet, a mere cloud of vapor; but it proved to be a world, and extended the[Page 174] boundaries of our solar system, in the moment of itsdiscovery, as much as all investigation had done in all previousages. Sir William Herschel was engaged in mapping stars in 1781, when hefirst observed its sea-green disk. He proposed to call it _GeorgiumSidus_, in honor of his king; but there were too many names of thegods in the sky to allow a mortal name to be placed among them. Itwas therefore called Uranus, since, being the most distant body ofour system, as was supposed, it might appropriately bear the nameof the oldest god. Finding anything in God's realms of infiniteriches ought not to lead men to regard that as final, but as apromise of more to follow. This planet had been seen five times by Flamsteed before its characterwas determined--once nearly a century before--and eight times byLe Monnier. These names, which might easily have been associatedwith a grand discovery, are associated with careless observation. Eyes were made not only to be kept open, but to have minds behindthem to interpret their visions. Herschel thought he discovered sixmoons belonging to Uranus, but subsequent investigation has limitedthe number to four. Two of these are seen with great difficulty bythe most powerful telescopes. If the plane of our moon's orbit were tipped up to a greaterinclination, revolving it on the line of nodes as an axis untilit was turned 85°, the moon, still continuing on its orbit in thatplane, would go over the poles instead of about the equator, andwould go back to its old path when the plane was revolved 180°;but its revolution would now be from east to west, or [Page 175]retrograde. The plane of the moons of Uranus has been thus inclinedtill it has passed 10° beyond the pole, and the moons' motions areretrograde as regards other known celestial movements. How Uranusitself revolves is not known. There are more worlds to conquer. NEPTUNE. God of the sea; sign [Symbol], his trident. DISTANCE FROM THE SUN, 2, 775, 000, 000 MILES. DIAMETER, 34, 500 MILES. VELOCITY PER MINUTE, 201. 6 MILES. AXIAL REVOLUTION UNKNOWN. ORBITAL, 164. 78 YEARS. ONE MOON. Men sought for Neptune as the heroes sought the golden fleece. The place of Uranus had been mapped for nearly one hundred yearsby these accidental observations. On applying the law of universalgravitation, a slight discrepancy was found between its computedplace and its observed place. This discrepancy was exceedinglyslight. In 1830 it was only 20"; in 1840, 190"; in 1884, 2'. Twostars that were 2' apart would appear as one to the keenest unaidedeye, but such an error must not exist in astronomy. Years of workwere given to its correction. Mr. John C. Adams, of Cambridge, England, finding that the attraction of a planet exterior to Uranuswould account for its irregularities, computed the place of sucha hypothetical body with singular exactness in October, 1841; butneither he nor the royal astronomer Airy looked for it. Anotheropportunity for immortality was heedlessly neglected. Meanwhile, M. Leverrier, of Paris, was working at the same problem. In thesummer of 1846 Leverrier announced the place of the exterior planet. The conclusion was in striking coincidence with that of Mr. [Page176] Clark. Mr. Challis commenced to search for the planet near theindicated place, and actually saw and mapped the star August 4th, 1846, but did not recognize its planetary character. Dr. Galle, ofBerlin, on the 23d of September, 1846, found an object with aplanetary disk not plotted on the map of stars. It was thesought-for world. It would seem easy to find a world seventy-sixtimes as large as the earth, and easy to recognize it when seen. Thefact that it could be discovered only by such care conveys anoverwhelming idea of the distance where it moves. [Illustration: Fig. 66. --Perturbation of Uranus. ] The effect of these perturbations by an exterior planet is understoodfrom Fig. 66. Uranus and Neptune were in conjunction, as shown, in 1822. But in 1820 it had been found that Uranus was too farfrom the sun, and too much accelerated. Since 1800, Neptune, inhis orbit from F to E, had been hastening Uranus in his orbit Dfrom C to B, and also drawing it farther from the sun. After 1822, Neptune, in passing from E to D, had been retarding Uranus in hisorbit from B to A. We have seen it is easy to miss immortality. There is still anotherinstance. Lalande saw Neptune on May 8th and 10th, 1795, noted thatit had moved a little, and that the observations did not agree;but, supposing the first was wrong, carelessly missed the gloryof once more doubling the bounds of the empire of the sun. [Page 177]It is time to pause and review our knowledge of this system. Thefirst view reveals a moon and earth endowed with a force of inertiagoing on in space in straight lines; but an invisible elastic cord ofattraction holds them together, just counterbalancing this tendencyto fly apart, and hence they circle round their centre of gravity. The revolving earth turns every part of its surface to the moon ineach twenty-four hours. By an axial revolution in the same timethat the moon goes round the earth, the moon holds the same pointof its surface constantly toward the earth. If we were to add one, two, four, eight moons at appropriate distances, the result wouldbe the same. There is, however, another attractive influence--thatof the sun. The sun attracts both earth and moon, but their neareraffection for each other keeps them from going apart. They both, revolving on their axes and around their centre of gravity, sweepin a vastly wider curve around the sun. Add as many moons as hasJupiter or Saturn, the result is the same--an orderly carryingof worlds through space. There lies the unsupported sun in the centre, nearer to infinityin all its capacities and intensities of force than our minds canmeasure, filling the whole dome to where the stars are set withlight, heat, and power. It holds five small worlds--Vulcan, Mercury, Venus, Earth, and Mars--within a space whose radius it would requirea locomotive half a thousand years to traverse. It next holds someindeterminate number of asteroids, and the great Jupiter, equal involume to 13, 000 earths. It holds Saturn, Uranus, and Neptune, andall their variously related satellites and rings. The two thoughtsthat overwhelm us are distance and power. The period of [Page 178]man's whole history is not sufficient for an express train totraverse half the distance to Neptune. Thought wearies and fails inseeking to grasp such distances; it can scarcely comprehend onemillion miles, and here are thousands of them. Even the wings ofimagination grow weary and droop. When we stand on that outermost ofplanets, the very last sentinel of the outposts of the king, thevery sun grown dim and small in the distance, we have taken only onestep of the infinite distance to the stars. They have not changedtheir relative position--they have not grown brighter by ourapproach. Neptune carries us round a vast circle about the centre ofthe dome of stars, but we seem no nearer its sides. In visitingplanets, we have been only visiting next-door neighbors in thestreets of a seaport town. We know that there are similar neighborsabout Sirius and Arcturus, but a vast sea rolls between. As we said, we stand with the outermost sentinel; but into the great void beyondthe king of day sends his comets as scouts, and they fly thousandsof years without for one instant missing the steady grasp of thepower of the sun. It is nearer almightiness than we are able tothink. If we cannot solve the problems of the present existence of worlds, how little can we expect to fathom the unsoundable depths of theircreation and development through ages measureless to man! Yet thevery difficulty provokes the most ambitious thought. We toil atthe problem because it has been hitherto unsolvable. Every errorwe make, and discover to be such, helps toward the final solution. Every earnest thinker who climbs the shining worlds as steps toa higher thought is trying to solve the problem God has given usto do. [Page 179]IX. THE NEBULAR HYPOTHESIS. "And the earth was without form, and void; and darkness was uponthe face of the deep. "--_Genesis_ i. 2. [Page 180] "A dark Illimitable ocean, without bound, Without dimension, where length, breadth, and height, And time, and place are lost. "--MILTON. "It is certain that matter is somehow directed, controlled, andarranged; while no material forces or properties are known to becapable of discharging such functions. "--LIONEL BEALE. "The laws of nature do not account for their own origin. "--JOHNSTUART MILL. [Page 181]IX. _THE NEBULAR HYPOTHESIS. _ The method by which the solar system came into its present formwas sketched in vast outline by Moses. He gave us the fundamentalidea of what is called the nebular hypothesis. Swedenborg, thatprodigal dreamer of vagaries, in 1734 threw out some conjectures ofthe way in which the outlines were to be filled up; Buffon followedhim closely in 1749; Kant sought to give it an ideal philosophicalcompleteness; as he said, "not as the result of observation andcomputation, " but as evolved out of his own consciousness; andLaplace sought to settle it on a mathematical basis. It has been modified greatly by later writers, and must receivestill greater modifications before it can be accepted by the bestscientists of to-day. It has been called "the grandest generalizationof the human mind;" and if it shall finally be so modified as to passfrom a tentative hypothesis to an accepted philosophy, declaringthe modes of a divine worker rather than the necessities of blindforce, it will still be worthy of that high distinction. Let it be clearly noted that it never proposes to do more than totrace a portion of the mode of working which brought the universefrom one stage to another. It only goes back to a definite point, never to absolute beginning, nor to nothingness. It takes matterfrom [Page 182] the hand of the unseen power behind, and merelynotes the progress of its development. It finds the clay in thehands of an intelligent potter, and sees it whirl in the process offormation into a vessel. It is not in any sense necessarilyatheistic, any more than it is to affirm that a tree grows by vitalprocesses in the sun and dew, instead of being arbitrarily andinstantly created. The conclusion reached depends on the spirit ofthe observer. Newton could say, "This most beautiful system of thesun, planets, and comets could only proceed from the counsel anddominion of an intelligent and powerful being!" Still it is well torecognize that some of its most ardent defenders have advocated itas materialistic. And Laplace said of it to Napoleon, "I have noneed of the hypothesis of a god. " The materialistic statement of the theory is this: that matteris at first assumed to exist as an infinite cloud of fire-mist, dowered with power latent therein to grow of itself into everypossibility of world, flower, animal, man, mind, and affection, without any interference or help from without. But it requiresfar more of the Divine Worker than any other theory. He must fillmatter with capabilities to take care of itself, and this wouldtax the abilities of the Infinite One far more than a constantsupervision and occasional interference. Instead of making thevase in perfect form, and coloring it with exquisite beauty byan ever-present skill, he must endow the clay with power to makeitself in perfect form, adorn itself with delicate beauty, andcreate other vases. The nebular hypothesis is briefly this: All the matter composingall the bodies of the sun, planets, and satellites once existedin an exceedingly diffused state; [Page 183] rarer than any gas withwhich we are acquainted, filling a space larger than the orbit ofNeptune. Gravitation gradually contracted this matter into acondensing globe of immense extent. Some parts would naturally bedenser than others, and in the course of contraction a rotarymotion, it is affirmed, would be engendered. Rotation would flattenthe globe somewhat in the line of its axis. Contracting still more, the rarer gases, aided by centrifugal force, would be left behind asa ring that would ultimately be separated, like Saturn's ring, fromthe retreating body. There would naturally be some places in thisring denser than others; these would gradually absorb all the ringinto a planet, and still revolve about the central mass, and stillrotate on its own axis, throwing off rings from itself. Thus theplanet Neptune would be left behind in the first sun-ring, to makeits one moon; the planet Uranus left in the next sun-ring, to makeits four moons from four successive planet-rings; Saturn, with itseight moons and three rings not made into moons, is left in thethird sun-ring; and so on down to Vulcan. The outer planets would cool off first, become inhabitable, and, as the sun contracted and they radiated their own heat, becomerefrigerated and left behind by the retreating sun. Of course theouter planets would move slowly; but as that portion of the sunwhich gave them their motion drew in toward the centre, keepingits absolute speed, and revolving in the lessening circles of acontracting body, it would give the faster motion necessary tobe imparted to Earth, Mercury, and Vulcan. The four great classes of facts confirmatory of this hypothesisare as follows: 1st. All the planets move [Page 184] in the samedirection, and nearly in the same plane, as if thrown off from oneequator; 2d. The motions of the satellites about their primaries aremostly in the same direction as that of their primaries about thesun; 3d. The rotation of most of these bodies on their axes, andalso of the sun, is in the same direction as the motion of theplanets about the sun; 4th. The orbits of the planets, excludingasteroids, and their satellites, have but a comparatively smalleccentricity; 5th. Certain nebulæ are observable in the heavenswhich are not yet condensed into solids, but are still bright gas. The materialistic evolutionist takes up the idea of a universe ofmaterial world-stuff without form, and void, but so endowed as todevelop itself into orderly worlds, and adds to it this exceedingadvance, that when soil, sun, and chemical laws found themselvesproperly related, a force in matter, latent for a million eons inthe original cloud, comes forward, and dead matter becomes alivein the lowest order of vegetable life; there takes place, as HerbertSpencer says, "a change from an indefinite, incoherent homogeneity, into a definite, coherent heterogeneity, through continuousdifferentiation and integration. " The dead becomes alive; matterpasses from unconsciousness to consciousness; passes up from plantto animal, from animal to man; takes on power to think, reason, love, and adore. The theistic evolutionist may think that the sameprocess is gone through, but that an ever-present and working Godsuperintends, guides, and occasionally bestows a new endowmentof power that successively gives life, consciousness, mental, affectional, and spiritual capacity. Is this world-theory true? and if so, is either of the [Page 185]evolution theories true also? If the first evolution theory is true, the evolved man will hardly know which to adore most, the Being thatcould so endow matter, or the matter capable of such endowment. There are some difficulties in the way of the acceptance of thenebular hypothesis that compel many of the most thorough scientistsof the day to withhold their assent to its entirety. The latest, andone of the most competent writers on the subject, Professor Newcomb, who is a mathematical astronomer, and not an easy theorist, evolvingthe system of the universe from the depth of his own consciousness, says: "Should any one be sceptical as to the sufficiency of theselaws to account for the present state of things, science can furnishno evidence strong enough to overthrow his doubts until the sunshall be found to be growing smaller by actual measurement, or thenebulæ be actually seen to condense into stars and systems. " Inone of the most elaborate defences of the theory, it is argued thatthe hypothesis explains why only one of the four planets nearestthe sun can have a moon, and why there can be no planet inside ofMercury. The discovery of the two satellites to Mars and of theplanet Vulcan makes it all the worse for these facts. Some of the objections to the theory should be known by every thinker. Laplace must have the cloud "diffused in consequence of excessiveheat, " etc. Helmholtz, in order to account for the heat of thecontracting sun, must have the cloud relatively cold. How he andhis followers diffused the cloud without heat is not stated. The next difficulty is that of rotation. The laws [Page 186] ofscience compel a contraction into one non-rotating body--a centralsun, indeed, but no planets about it. Laplace cleverly evades thedifficulty by not taking from the hand of the Creator diffused gas, but a sun with an atmosphere filling space to the orbit of Neptune, and _already in revolution_. He says: "It is four millions to onethat all motions of the planets, rotations and revolutions, were atonce imparted by an original common cause, of which we know neitherthe nature nor the epoch. " Helmholtz says of rotation, "theexistence of which must be assumed. " Professor Newcomb says that theplanets would not be arranged as now, each one twice as far from thesun as the next interior one, and the outer ones made first, butthat all would be made into planets at once, and the small innerones quite likely to cool off more rapidly. It is a very serious difficulty that at least one satellite doesnot revolve in the right direction. How Neptune or Uranus couldthrow their moons backward from its equator is not easily accountedfor. It is at least one Parthian arrow at the system, not necessarilyfatal, but certainly dangerous. A greater difficulty is presented by the recently discovered satellitesof Mars. The inner one goes round the planet in one-third part ofthe time of the latter's revolution. How Mars could impart threetimes the speed to a body flying off its surface that it has itself, has caused several defenders of the hypothesis to rush forwardwith explanations, but none with anything more than mere imaginarycollisions with some comet. It is to be noticed that accounting forthree times the speed is not enough; for as Mars shrunk away fromthe [Page 187] ring that formed that satellite, it ought itself toattain more speed, as the sun revolves faster than its planets, andthe earth faster than its moon. In defending the hypothesis, Mitchelsaid: "Suppose we had discovered that it required more time forSaturn or Jupiter to rotate on their axes than for their nearestmoon to revolve round them in its orbit; this would have falsifiedthe theory. " It is also asserted that the newly discovered planetVulcan makes an orbital in less time than the sun makes an axialrevolution. In regard to one Martial moon, Professor Kirkwood, on whom Proctorconferred the highest title that could be conferred, "the modernKepler, " says: "Unless some explanation can be given, the short periodof the inner satellite will be doubtless regarded as a conclusiveargument against the nebular hypothesis. " If gravitation be sufficientto account for the various motions of the heavenly bodies, we havea perplexing problem in the star known as 1830 Groombridge, nowin the Hunting Dogs of Bootes. It is thought to have a speed oftwo hundred miles per second--a velocity that all the known matterin the universe could not give to the star by all its combinedattraction. Neither could all that attraction stop the motion ofthe star, or bend it into an orbit. Its motion must be accountedfor on some hypothesis other than the nebular. The nebulæ which we are able to observe are not altogether confirmatoryof the hypothesis under consideration. They have the most fantasticshapes, as if they had no relation to rotating suns in the formativestages. There are vast gaps in the middle, where they ought to bedensest. Mr. Plumer, in the _Natural Science Review_, [Page 188]says, in regard to the results of the spectroscopic revelations: "Weare furnished with distinct proof that the gases so examined are notonly of nearly equal density, but that they exist in a low state of_tension. This fact is fatal to the nebular theory. _" In the autumn of 1876 a star blazed out in Cygnus, which promisedto throw a flood of light on the question of world-making. Itsspectrum was like some of the fixed stars. It probably blazed ontby condensation from some previously invisible nebula. But itsbrilliancy diminished swiftly, when it ought to have taken millionsof years to cool. If the theory was true, it ought to have behavedvery differently. It should have regularly condensed from gas to asolid sun by slow process. But, worst of all, after being a starawhile, it showed unmistakable proofs of turning into a cloud-mist--astar into a nebula, instead of _vice versa_. A possible explanationwill be considered under variable stars. Such are a few of the many difficulties in the way of acceptingthe nebular hypothesis, as at present explained, as being the truemode of development of the solar system. Doubtless it has comefrom a hot and diffused condition into its present state; but whensuch men as Proctor, Newcomb, and Kirkwood see difficulties thatcannot be explained, contradictions that cannot be reconciled bythe principles of this theory, surely lesser men are obliged tosuspend judgment, and render the Scotch verdict of "not proven. "Whatever truth there may be in the theory will survive, and beincorporated into the final solution of the problem; which solutionwill be a much grander generalization of the human mind than thenebular hypothesis. [Page 189]Of some things we feel very sure: that matter was once withoutform and void, and darkness rested on the face of the mighty deeps;that, instead of chaos, we have now cosmos and beauty; and thatthere is some process by which matter has been brought from onestate to the other. Whether, however, the nebular hypothesis laysdown the road travelled to this transfiguration, we are not sure. Some of it seems like solid rock, and some like shifting quicksand. Doubtless there is a road from that chaos to this fair cosmos. The nebular hypothesis has surveyed, worked, and perfected manylong reaches of this road, but the rivers are not bridged, thechasms not filled, nor the mountains tunnelled. When men attempt to roll the hypothesis of evolution along theroad of the nebular hypothesis of worlds, and even beyond to theproduction of vegetable and animal life, mind and affection, thegaps in the road become evident, and disastrous. A soul that has reached an adoration for the Supreme Father caresnot how he has made him. Doubtless the way God chose was the best. It is as agreeable to have been thought of and provided for in thebeginning, to have had a myriad ages of care, and to have comefrom the highest existent life at last, as to have been made atonce, by a single act, out of dust. The one who is made is not tosay to the Maker, "Why hast thou formed me in this or that manner?"We only wish the question answered in what manner we were reallymade. Evolution, without constant superintendence and occasional newinspiration of power, finds some tremendous chasms in the roadit travels. These must be spanned by the power of a present Godor the airy imagination [Page 190] of man. Dr. McCosh has happilyenumerated some of these tremendous gaps over which mere forcecannot go. Given, then, matter with mechanical power only, what arethe gaps between it and spirituality? "1. Chemical action cannot be produced by mechanical power. "2. Life, even in the lowest forms, cannot be produced from unorganizedmatter. "3. Protoplasm can be produced only by living matter. "4. Organized matter is made up of cells, and can be produced onlyby cells. Whence the first cell? "5. A living being can be produced only from a seed or germ. Whencethe first vegetable seed? "6. An animal cannot be produced from a plant. Whence the firstanimal? "7. Sensation cannot be produced in insentient matter. "8. The genesis of a new species of plant or animal has never comeunder the cognizance of man, either in pre-human or post-human ages, either in pre-scientific or scientific times. Darwin acknowledgesthis, and says that, should a new species suddenly arise, we haveno means of knowing that it is such. "9. Consciousness--that is, a knowledge of self and itsoperations--cannot be produced out of mere matter or sensation. "10. We have no knowledge of man being generated out of the loweranimals. "11. All human beings, even savages, are capable of forming certainhigh ideas, such as those of God and duty. The brute creaturescannot be made to entertain these by any training. [Page 191]"With such tremendous gaps in the process, the theory which wouldderive all things out of matter by development is seen to be avery precarious one. The truth, according to the best judgment to be formed in the presentstate of knowledge, would seem to be about this: The nebular hypothesisis correct in all the main facts on which it is based; but that neitherthe present forces of matter, nor any other forces conceivable tothe mind of man, with which it can possibly be endowed, can accountfor all the facts already observed. There is a demand for a personalvolition, for an exercise of intelligence, for the following of adivine plan that embraces a final perfection through various andchangeful processes. The five great classes of facts that sustainthe nebular hypothesis seem set before us to show the regular orderof working. The several facts that will not, so far as at presentknown, accord with that plan, seem to be set before us to declarethe presence of a divine will and power working his good pleasureaccording to the exigencies of time and place. [Page 193]X. THE STELLAR SYSTEM. "The heavens number out the glory of the strong God. "--DAVID. [Page 194]Richter says that "an angel once took a man and stripped him ofhis flesh, and lifted him up into space to show him the glory ofthe universe. When the flesh was taken away the man ceased to becowardly, and was ready to fly with the angel past galaxy aftergalaxy, and infinity after infinity, and so man and angel passedon, viewing the universe, until the sun was out of sight--untilour solar system appeared as a speck of light against the blackempyrean, and there was only darkness. And they looked onward, and in the infinities of light before, a speck of light appeared, and suddenly they were in the midst of rushing worlds. But theypassed beyond that system, and beyond system after system, andinfinity after infinity, until the human heart sank, and the mancried out: 'End is there none of the universe of God?' The angelstrengthened the man by words of counsel and courage, and they flewon again until worlds left behind them were out of sight, and specksof light in advance were transformed, as they approached them, intorushing systems; they moved over architraves of eternities, overpillars of immensities, over architecture of galaxies, unspeakable indimensions and duration, and the human heart sank again and calledont: 'End is there none of the universe of God?' And all the starsechoed the question with amazement: 'End is there none of the universeof God?' And this echo found no answer. They moved on again pastimmensities of immensities, and eternities of eternities, untilin the dizziness of uncounted galaxies the human heart sank forthe last time, and called out: 'End is there none of the universeof God?' And again all the stars repeated the question, and theangel answered: 'End is there none of the universe of God. Lo, also, there is no beginning. '" [Page 195]X. _THE OPEN PAGE OF THE HEAVENS. _ The Greeks set their mythological deities in the skies, and readthe revolving pictures as a starry poem. Not that they were thefirst to set the blazonry of the stars as monuments of their thought;we read certain allusions to stars and asterisms as far back asthe time of Job. And the Pleiades, Arcturus, and Orion are some ofthe names used by Him who "calleth all the stars by their names, in the greatness of his power. " Homer and Hesiod, 750 B. C. , alludeto a few stars and groups. The Arabians very early speak of theGreat Bear; but the Greeks completely nationalized the heavens. They colonized the earth widely, but the heavens completely; andnightly over them marched the grand procession of their apotheosizeddivinities. There Hercules perpetually wrought his mighty laborsfor the good of man; there flashed and faded the changeful starAlgol, as an eye in the head of the snaky-haired Medusa; over themflew Pegasus, the winged horse of the poet, careering among thestars; there the ship Argo, which had explored all strange seasof earth, nightly sailed in the infinite realms of heaven; therePerseus perpetually killed the sea-monster by celestial aid, andperpetually won the chained Andromeda for his bride. Very evidentwas their recognition of divine help: equally evident was [Page 196]their assertion of human ability and dominion. They gathered theillimitable stars, and put uncountable suns into the shape of theGreat Bear--the most colossal form of animal ferocity andstrength--across whose broad forehead imagination grows weary inflying; but they did not fail to put behind him a representative ofthemselves, who forever drives him around a sky that never sets--aperpetual type that man's ambition and expectation correspond tothat which has always been revealed as the divine. The heavens signify much higher power and wisdom to us; we retain theold pictures and groupings for the convenience of finding individualstars. It is enough for the astronomer that we speak of a star assituated right ascension 13' 45", declination 88° 40'. But formost people, if not all, it is better to call it Polaris. So wemight speak of a lake in latitude 42° 40', longitude 79° 22', butit would be clearer to most persons to say Chatauqua. For exactlocation of a star, right ascension and declination must be given;but for general indication its name or place in a constellationis sufficiently exact. The heaven is rather indeterminably laidout in irregular tracts, and the mythological names are preserved. The brightest stars are then indicated in order by the letters ofthe Greek alphabet--Alpha (a), Beta (b), Gamma (g), etc. Afterthese are exhausted, the Roman alphabet is used in the same manner, and then numbers are resorted to; so that the famous star 61 Cygniis the 111th star in brightness in that one constellation. Anacquaintance with the names, peculiarities, and movements of thestars visible at different seasons of the year is an unceasingsource of pleasure. It [Page 197] is not vision alone that isgratified, for one fine enough may hear the morning stars singtogether, and understand the speech that day uttereth unto day, andthe knowledge that night showeth unto night. One never can be aloneif he is familiarly acquainted with the stars. He rises early in thesummer morning, that he may see his winter friends; in winter, thathe may gladden himself with a sight of the summer stars. He hailstheir successive rising as he does the coming of his personalfriends from beyond the sea. On the wide ocean he is commercing withthe skies, his rapt soul sitting in his eyes. Under the clear skiesof the East he hears God's voice speaking to him, as to Abraham, andsaying, "Look now toward the heavens, and tell the number of thestars, if thou be able to number them. " A general acquaintance with the stars will be first attempted;a more particular knowledge afterward. Fig. 67 (page 201) is amap of the circumpolar region, which is in full view every clearnight. It revolves daily round Polaris, its central point. Towardthis star, the two end stars of the Great Dipper ever point, andare in consequence called "the Pointers. " The map may be held towardthe northern sky in such a position as the stars may happen to be. The Great Bear, or Dipper, will be seen at nine o'clock in theevening above the pole in April and May; west of the pole, thePointers downward, in July and August; close to the north horizonin October and November; and east of the pole the Pointers highest, in January and February. The names of such constantly visible starsshould be familiar. In order, from the end of the tail of the GreatBear, we have Benetnasch ae, Mizar z, Little Alcor close to it, [Page 198] Alioth, e Megrez, d at the junction, has been growingdimmer for a century, Phad, g Dubhe and Merak. It is best to getsome facility at estimating distances in degrees. Dubhe and Merak, "the Pointers, " are five degrees apart. Eighteen degrees forward ofDubhe is the Bear's nose; and three pairs of stars, fifteen degreesapart, show the position of the Bear's three feet. Follow "thePointers" twenty-nine degrees from Dubhe, and we come to thepole-star. This star is double, made of two suns, both appearing asone to the naked eye. It is a test of an excellent three-inchtelescope to resolve it into two. Three stars beside it make thecurved-up handle of the Little Dipper of Ursa Minor. Between the twoBears, thirteen degrees from Megrez, and eleven degrees from Mizar, are two stars in the tail of the Dragon, which curves about toappropriate all the stars not otherwise assigned. Follow a curve offifteen stars, doubling back to a quadrangle from five to threedegrees on a side, and thirty-five degrees from the pole, for hishead. His tongue runs out to a star four degrees in front. We shallfind, hereafter, that the foot of Hercules stands on this head. Thisis the Dragon slain by Cadmus, and whose teeth produced such a cropof sanguinary men. The star Thuban was once the pole-star. In the year B. C. 2300 itwas ten times nearer the pole than Polaris is now. In the yearA. D. 2100 the pole will be within 30' of Polaris; in A. D. 7500, it will be at a of Cepheus; in A. D. 13, 500, within 7° of Vega; inA. D. 15, 700, at the star in the tongue of Draco; in A. D. 23, 000, at Thuban; in A. D. 28, 000, back to Polaris. This indicates no changein the position of the dome [Page 199] of stars, but a change in thedirection of the axis of the earth pointing to these various placesas the cycles pass. As the earth goes round its orbit, the axis, maintaining nearly the same direction, really points to every partof a circle near the north star as large as the earth's orbit, thatis, 185, 000, 000 miles in diameter. But, as already shown, thatcircle is too small to be discernible at our distance. The widecircle of the pole through the ages is really made up of theinterlaced curves of the annual curves continued through 25, 870years. The stem of the spinning top wavers, describes a circle, andfinally falls; the axis of the spinning earth wavers, describes acircle of nearly 28, 000 years, and never falls. The star g Draconis, also called Etanin, is famous in modern astronomy, because observations on this star led to the discovery of the_aberration of light_. If we held a glass tube perpendicularly outof the window of a car at rest, when the rain was falling straightdown, we could see the drops pass directly through. Put the carin motion, and the drops would seem to start toward us, and thetop of the tube must be bent forward, or the drops entering wouldstrike on the backside of the tube carried toward them. So ourtelescopes are bent forward on the moving earth, to enable theentered light to reach the eye-piece. Hence the star does not appearjust where it is. As the earth moves faster in some parts of itsorbit than others, this aberration is sometimes greater than atothers. It is fortunate that light moves with a uniform velocity, or this difficult, problem would be still further complicated. The displacement of a star from this course is about 20". 43. [Page 200]On the side of Polaris, opposite to Ursa Major, is King Cepheus, made of a few dim stars in the form of the letter K. Near by ishis brilliant wife Cassiopeia, sitting on her throne of state. They were the graceless parents who chained their daughter to arock for the sea-monster to devour; but Perseus, swift with thewinged sandals of Mercury, terrible with his avenging sword, andinvincible with the severed head of Medusa, whose horrid aspect ofsnaky hair and scaly body turned to stone every beholder, rescuesthe maiden from chains, and leads her away by the bands of love. Nothing could be more poetical than the life of Perseus. When hewent to destroy the dreadful Gorgon, Medusa, Pluto lent him hishelmet, which would make him invisible at will; Minerva loanedher buckler, impenetrable, and polished like a mirror; Mercurygave him a dagger of diamonds, and his winged sandals, which wouldcarry him through the air. Coming to the loathsome thing, he wouldnot look upon her, lest he, too, be turned to stone; but, guidedby the reflection in the buckler, smote off her head, carried ithigh over Libya, the dropping blood turning to serpents, whichhave infested those deserts ever since. [Illustration: Fig. 67. --Circumpolar Constellations. Always visible. In this position. --January 20th, at 10 o'clock; February 4th, at9 o'clock; and February 19th, at 8 o'clock. ] The human mind has always been ready to deify and throne in theskies the heroes that labor for others. Both Perseus and Herculesare divine by one parent, and human by the other. They go up anddown the earth, giving deliverance to captives, and breaking everyyoke. They also seek to purge away all evil; they slay dragons, gorgons, devouring monsters, cleanse the foul places of earth, and one of them so wrestles with death as to win a victim from hisgrasp. Finally, by [Page 201] an ascension in light, they go up tobe in light forever. They are not ideally perfect. They right wrongby slaying wrong-doers, rather than by being crucified themselves;they are just murderers; but that only plucks the fruit from thetree of evil. They never attempted to infuse a holy life. Theypunished rather than regenerated. It must be confessed, also, thatthey were not sinless. But they were the best saviors the race couldimagine, and are examples of that perpetual effort of the human mindto incarnate a Divine Helper who shall labor and die for the good ofmen. [Page 202][Illustration: Fig. 68. --Algol is on the Meridian, 51° South ofPole. --At 10 o'clock, December 7th; 9 o'clock, December 22d; 8o'clock, January 5th. ] _Equatorial Constellations. _ If we turn our backs on Polaris on the 10th of November, at 10o'clock in the evening, and look directly overhead, we shall seethe beautiful constellation of Andromeda. Together with the squareof Pegasus, it makes another enormous dipper. The star a Alpheratzis in her face, the three at the left cross her breast. B and thetwo above mark the girdle of her loins, and g is in the foot. Perseusis near enough for help; and Cetus, the sea-monster, is far enoughaway to do no harm. Below, and east of Andromeda, is the Ram ofthe golden fleece, recognizable by the three stars in an acutetriangle. The brightest is called Arietis, or Hamel. East of thisare the Pleiades, and the V-shaped Hyades in Taurus, or the Bull. The Pleiades rise about 9 o'clock on the evening of the 10th ofSeptember, and at 3 o'clock A. M. On June 10th. [Page 203][Illustration: Fig. 69. --Capella (45° from the Pole) and Rigel(100°) are on the Meridian at 8 o'clock February 7th, 9 o'clockJanuary 22d, and at 10 o'clock January 7th. ] Fig. 69 extends east and south of our last map. It is the mostgorgeous section of our heavens. (See the Notes to the Frontispiece. )Note the triangle, 26° on a side, made by Betelguese, Sirius, andProcyon. A line from Procyon to Pollux leads quite near to Polaris. Orion is the mighty hunter. Under his feet is a hare, behind himare two dogs, and before him is the rushing bull. The curve ofstars to the right of Bellatrix, g, represents his shield of theNemean lion's hide. The three stars of his belt make a measure3° long; the upper one, Mintaker, is less than 30' south of theequinoctial. The ecliptic passes between Aldebaran and the Pleiades. Sirius rises about 9 o'clock P. M. On the 1st of December, and about4 o'clock A. M. On the 16th of August. Procyon rises about half anhour earlier. [Page 204][Illustration: Fig. 70--Regulus comes on the Meridian, 79° southfrom the Pole, at 10 o'clock March 23d, 9 o'clock April 8th, andat 8 o'clock April 23d. ] Fig. 70 continues eastward. Note the sickle in the head and neckof the Lion. The star b is Denebola, in his tail. Arcturus appearsby the word Bootes, at the edge of the map. These two stars makea triangle with Spica, about 35° on a side. The geometric head ofHydra is easily discernible east of Procyon: The star g in theVirgin is double, with a period of 145 years. Z is just above theequinoctial. There is a fine nebula two-thirds of the way from d toae, and a little above the line connecting the two. Coma Berenicesis a beautiful cluster of faint stars. Spica rises at 9 o'clock onthe 10th of February, at 5 o'clock A. M. On the 6th of November. [Page 205][Illustration: Fig. 7l. --Arcturus comes to the Meridian, 70° fromthe Pole, at 10 o'clock May 25th, 9 o'clock June 9th, and at 8o'clock June 25th. ] Fig. 71 represents the sky to the eastward and northward of thelast. A line drawn from Polaris and Benetnasch comes east of Arcturusto the little triangle called his sons. Bootes drives the GreatBear round the pole. Arcturus and Denebola make a triangle witha, also called Cor Coroli, in the Hunting Dogs. This triangle, andthe one having the same base, with Spica for its apex, is calledthe "Diamond of the Virgin. " Hercules appears head down--a in theface, b, g, d; in his shoulders, p; and ae; in the loins, t in theknee, the foot being bent to the stars at the right. The Serpent'shead, making an X, is just at the right of the g of Hercules, andthe partial circle of the Northern Crown above. The head of Dracois seen at b on the left of the map. Arcturus rises at 9 o'clockabout the 20th of February, and at 5 A. M. On the 22d of October;Regulus 3h. 35m. Earlier. [Page 206][Illustration: Fig. 72. --Altair comes to the Meridian, 82° fromthe Pole, at 10 o'clock P. M. August 18th, at 9 o'clock September2d, and at 8 o'clock September 18th. ] Fig. 72 portrays the stars eastward and southward. Scorpio is oneof the most brilliant and easily traced constellations. Antares, a, in the heart, is double. In Sagittarius is the Little Milk-dipper, and west of it the bended bow. Vega is at the top of the map. Nearit observe z, a double, and e, a quadruple star. The point to whichthe solar system is tending is marked by the sign of the earthbelow p; Herculis. The Serpent, west of Hercules, and coiled roundnearly to Aquila, is very traceable. In the right-hand lower corneris the Centaur. Below, and always out of our sight, is the famousa Centauri. The diamond form of the Dolphin is sometimes called"Job's Coffin. " The ecliptic passes close [Page 207] to b ofScorpio, which star is in the head. Antares, in Scorpio, rises at 9o'clock P. M. On May 9th, and at 5 o'clock A. M. On January 5th. [Illustration: Fig. 73. --Fomalhaut comes to the Meridian, only 17°from the horizon, at 8 o'clock November 4th. ] In Fig. 73 we recognize the familiar stars of Pegasus, which tellus we have gone quite round the heavens. Note the beautiful crossin the Swan. B in the bill is named Albireo, and is a beautifuldouble to almost any glass. Its yellow and blue colors are verydistinct. The place of the famous double star 61 Cygni is seen. Thefirst magnitude star in the lower left-hand corner is Fomalhaut, inthe Southern Fish. A Pegasi is in the diagonal corner from Alpharetz, in Andromeda. The star below Altair is b Aquilæ, and is calledAlschain; the one above is g Aquilæ, named Tarazed. This is nota brilliant section of the sky. Altair rises at 9 o'clock on the29th of May, and at 6 o'clock A. M. On the 11th of January. [Page 208][Illustration: Fig. 74. --Southern Circumpolar Constellations invisiblenorth of the Equator. ] Fig. 74 gives the stars that are never seen by persons north ofthe earth's equator. In the Ship is brilliant Canopus, and theremarkable variable ae. Below it is the beautiful Southern Cross, near the pole of the southern heavens. Just below are the two firstmagnitude stars Bungala, a, and Achernar, b, of the Centaur. Sucha number of unusually brilliant stars give the southern sky anunequalled splendor. In the midst of them, as if for contrast, is the dark hole, called by the sailors the "Coal-sack, " whereeven the telescope reveals no sign of light. Here, also, are thetwo Magellanic clouds, both easily discernible by the naked eye;the larger two hundred times the apparent size of the moon, lyingbetween the pole and Canopus, and the other between Achernar andthe pole. The smaller cloud is only one-fourth the size of theother. Both are mostly resolvable into groups of stars from thefifth to the fifteenth magnitude. [Page 209]For easy out-door finding of the stars above the horizon at anytime, see star-maps at end of the book. _Characteristics of the Stars. _ Such a superficial examination of stars as we have made scarcelytouches the subject. It is as the study of the baptismal register, where the names were anciently recorded, without any knowledgeof individuals. The heavens signify much more to us than to theGreeks. We revolve under a dome that investigation has infinitelyenlarged from their estimate. Their little lights were turned byclumsy machinery, held together by material connections. Our vastworlds are connected by a force so fine that it seems to pass outof the realm of the material into that of the spiritual. Animalferocity or a human Hercules could image their idea of power. Oursfinds no symbol, but rises to the Almighty. Their heavens were fullof fighting Orions, wild bulls, chained Andromedas, and devouringmonsters. Our heavens are significant of harmony and unity; allworlds carried by one force, and all harmonized into perfect music. All their voices blend their various significations into a personalspeaking, which says, "Hast thou not heard that the everlastingGod, the Lord, the creator of the ends of the earth, fainteth not, neither is weary?" There is no searching of his understanding. Lift up your eyes on high, and behold who hath created all thesethings, that brought out their host by number, that calleth themall by their names in the greatness of his power; for that he isstrong in power not one faileth. [Page 210]_Number. _ We find about five thousand stars visible to the naked eye in thewhole heavens, both north and south. Of these twenty are of thefirst magnitude, sixty-five of the second, two hundred of the third, four hundred of the fourth, eleven hundred of the fifth, and threethousand two hundred of the sixth. We think we can easily numberthe stars; but train a six-inch telescope on a little section of theTwins, where six faint stars are visible, and over three thousandluminous points appear. The seventh magnitude has 13, 000 stars;the eighth, 40, 000; the ninth, 142, 000. There are 18, 000, 000 starsin the zone called the Milky Way. When our eyes are not sensitiveenough to be affected by the light of far-off stars the tastimetrefeels their heat, and tells us the word of their Maker is true--"theyare innumerable. "[*] [Footnote *: _Telescopic Work. _--Look at the Hyades and Pleiadesin Taurus. Notice the different colors of stars in them both. Findthe cluster Præsepe in Fig. 70, just a trifle above a point midwaybetween Procyon and Regulus. It is equally distant from Procyon anda point a little below Pollux. Sweep along the Milky Way almostanywhere, and observe the distribution of stars; in some placesperfect crowds, in others more sparsely scattered. Find with thenaked eye the rich cluster in Perseus. Draw a line from Algol toa of Perseus (Fig. 67); turn at right angles to the right, at adistance of once and four-tenths the first line a brightness willbe seen. The telescope reveals a gorgeous cluster. ] _Double and Multiple Stars. _ If we look up during the summer months nearly overhead at the stare Lyra, east of Vega (Fig. 72), we shall see with the naked eyethat the star appears a little [Page 211] elongated. Turn youropera-glass upon it, and two stars appear. Turn a larger telescopeon this double star, and each of the components separate into two. It is a double double star. We know that if two stars are near inreality, and not simply apparently so by being in the same line ofsight, they must revolve around a common centre of gravity, or rushto a common ruin. Eagerly we watch to see if they revolve. A fewyears suffice to show them in actual revolution. Nay, the movementof revolution has been decided before the companion star wasdiscovered. Sirius has long been known to have a proper motion, suchas it would have if another sun were revolving about it. Even thedirection of the unseen body could always be indicated. In February, 1862, Alvan Clark, artist, poet, and maker of telescopes (whichrequires even greater genius than to be both poet and artist), discovered the companion of Sirius just in its predicted place. As amatter of fact, one of Mr. Clark's sons saw it first; but their fameis one. The time of revolution of this pair is fifty years. But onecompanion does not meet the conditions of the movements. Here mustalso be one or more planets too small or dark to be seen. The doublestar x in the Great Bear (see Fig. 70) makes a revolution infifty-eight years. Procyon moves in an orbit which requires the presence of a companionstar, but it has as yet eluded our search. Castor is a double star;but a third star or planet, as yet undiscovered, is required toaccount for its perturbations. Men who discovered Neptune by theperturbations of Uranus are capable of judging the cause of theperturbations of suns. We have spoken of [Page 212] the whole orbitof the earth being invisible from the stars. The nearest star in ournorthern hemisphere, 61 Cygni, is a telescopic double star; theconstituent parts of it are forty-five times as far from each otheras the earth is from the sun, yet it takes a large telescope to showany distance between the stars. [*] [Footnote *: _Telescopic Work. _--Only such work will be laid outhere as can be done by small telescopes of from two to four inchobject-glasses. The numbers in Fig. 75 correspond to those of thetable. --------------------------------------------------------------------| | | |Dist. Of|Magni-| ||No. | Name. | Fig. | Parts. |tudes. | Remarks. ||---|------------|-------------|--------|------|---------------------|| 1. | e Lyræ | 72 | 1' 56" | |Quadruple. || 2. | z Lyræ | 72 | 44 |5 & 6 |Topaz and green. || 3. | b Cygni | 73 | 34-1/2|3 & 6 |Yellow and blue. || 4. | 61 Cygni | 73 | 20 |5 & 6 |Nearest star but one. || 5. | Mizar | 67 | 14 |3 & 4 |Both white. || 6. | Polaris | 67 | 18-1/2|2 & 9 |Test object of eye || | | | | | and glass. || 7. | r Orionis |Frontispiece. | 7 |5 & 8 |Yellow and blue. || 8. | b Orionis | " | 9 |1 & 8 | Rigel. || 9. | d " | " | 10 |2 & 8 | Red and white. ||10. | th " | " | | |Septuple. ||11. | l " | " | 5 | |White and violet. ||12. | s " | " A, B. | 11 |4 & 10|Octuple. ||13. | Castor | 69 | 5-1/2|2 & 3 |White. ||14. | Pollux | 69 | |Triple|Orange, gray, lilac. ||15. | g Virginis | 70 | 5 |3 & 3 |Both yellow. | --------------------------------------------------------------------] When g Virginis was observed in 1718 by Bradley, the componentparts were 7" asunder. He incidentally remarked in his note-bookthat the line of their connection was parallel to the line of thetwo stars Spica, or a and d Virginis. By 1840 they were not morethan 1" apart, and the line of their connection greatly changed. The appearance of the star is given in Fig. 75 (15), commencingat the left, for the years 1837 '38 '39 '40 '45 '50 '60 and '79. Also a conjectural [Page 213] orbit, placed obliquely, and theposition of the stars at the times mentioned, commencing at the top. The time of its complete revolution is one hundred and fifty years. [Illustration: Fig. 75. --Aspects and Revolution of Double Stars. ] The meaning of these double stars is that two or more suns revolveabout their centre of gravity, as the moon and earth about theircentre. If they have planets, as doubtless they have, the movementis no more complicated than the planets we call satellites of Saturnrevolving about their central body, and also about the sun. KindleSaturn and Jupiter to a blaze, or let out their possible light, andour system would appear a triple star in the distance. Doubtless, in the far past, before these giant planets were cooled, it soappeared. We find some stars double, others triple, quadruple, octuple, andmultiple. It is an extension of the same principles that governour system. Some of these suns are so far asunder that they canswing their Neptunes between them, with less perturbation thanUranus and Neptune have in ours. Light all our planets, and therewould be a multiple star with more or less suns seen, [Page 214]according to the power of the instrument. Perhaps the octuple stars in Orion differs in no respect from our system, except in thesize and distance of its separate bodies, and less cooling, eitherfrom being younger, or from the larger bodies cooling more slowly. Suns are of all ages. Infinite variety fills the sky. It is aspreposterous to expect that every system or world should have analogouscircumstances to ours at the present time, as to insist that everymember of a family should be of the same age, and in the same stateof development. There are worlds that have not yet reached theconditions of habitability by men, and worlds that have passedthese conditions long since. Let them go. There are enough left, and an infinite number in the course of preparation. Some are fineand lasting enough to be eternal mansions. _Colored Stars. _ In the cloudy morning we get only red light, but the sun is white. So Aldebaran and Betelguese may be girt by vapors, that only thestrong red rays can pass. Again, an iron moderately heated givesout dull red light; becoming hotter, it emits white light. Sirius, Regulus, Vega, and Spica may be white from greater intensity ofvibration. Procyon, Capella, and Polaris are yellow from less intensityof vibration. Again, burn salt in a white flame, and it turns toyellow; mix alcohol and boracic acid, ignite them, and a beautifulgreen flame results; alcohol and nitrate of strontia give red flame;alcohol and nitrate of barytes give yellow flame. So the compositionof a sun, or the special development of anyone substance thereofat any time, may determine the color of a star. [Page 215]The special glory of color in the stars is seen in the marked contrastspresented in the double and multiple stars. The larger star isusually white, still in the intensity of heat and vibration; theothers, smaller, are somewhat cooled off, and hence present colorslower down the scale of vibration, as green, yellow, orange, andeven red. That stars should change color is most natural. Many causes wouldproduce this effect. The ancients said Sirius was red. It is nowwhite. The change that would most naturally follow mere age andcooling would be from white, through various colors, to red. We arecharmed with the variegated flowers of our gardens of earth, buthe who makes the fields blush with flowers under the warm kisses ofthe sun has planted his wider gardens of space with colored stars. "The rainbow flowers of the footstool, and the starry flowers ofthe throne, " proclaim one being as the author of them all. _Clusters of Stars. _ From double and multiple we naturally come to groups and clusters. Allusion has been made to the Hyades, Pleiades, etc. Everyone hasnoticed the Milky Way. It seems like two irregular streams of compactedstars. It is not supposed that they are necessarily nearer togetherthan the stars in the sparse regions about the pole. But the 18, 000, 000suns belonging to our system are arranged within a space representedby a flattened disk. If one hundred lights, three inches apart, are arranged on a hoop ten feet in diameter, they would be in acircle. Add a thousand or two more the same distance apart, fillingup the centre, and [Page 216] extending a few inches on each side ofthe inner plane of the hoop: an eye in the centre, looking outtoward the edge, would see a milky way of lights; looking out towardthe sides or poles, would see comparatively few. It would seem as ifthis oblate spheroidal arrangement was the result of a revolution ofall the suns composing the system. Jupiter and earth are flattenedat the poles for the same reason. [Illustration: Fig. 76. --Sprayed Cluster below ae in Hercules. ] [Illustration: Fig. 77. --Globular Cluster. ] In various parts of the heavens there are small globular well-definedclusters, and clusters very irregular in form, marked with spraysof stars. There is a cluster of this latter class in Hercules, just under the S, in Fig. 72. "Probably no one ever saw it with agood telescope without a shout of wonder. " Here is a cluster of theformer class represented in Fig. 77. "The noble globular cluster, o Centauri is beyond all comparison the richest and largest objectof the kind in the heavens. Its stars are literally innumerable;and as their total light, when received by the naked eye, affectsit hardly more than a star of the fifth to fourth[Page 217]magnitude, the minuteness of each star may be imagined. " There are two possibilities of thought concerning these clusters. Either that they belong to our stellar system, and hence the starsmust be small and young, or they are another universe of millionsof suns, so far way that the inconceivable distances between thestars are shrunken to a hand's-breadth, and their unbearable splendorof innumerable suns can only make a gray haze at the distance atwhich we behold them. The latter is the older and grander thought;the former the newer and better substantiated. _Nebulæ. _ The gorgeous clusters we have been considering appear to the eyeor the small telescope as little cloudlets of hazy light. One afteranother were resolved into stars; and the natural conclusion was, that all would yield and reveal themselves to be clustered suns, when we had telescopes of sufficient power. But the spectroscope, seeing not merely form but substance also, shows that some of themare not stars in any sense, but masses of glowing gas. Two of thesenebulæ are visible to the naked eye: one in Andromeda (see Fig. 68), and one around the middle star of the sword of Orion, shownin Fig. 78. A three-inch telescope resolves th Orionis into thefamous trapezium, and a nine-inch instrument sees two stars more. The shape of the nebula is changeable, and is hardly suggestive ofthe moulding influence of gravitation. It is probably composed ofglowing nitrogen and hydrogen gases. Nebulæ are of all conceivableshapes--circular, annular, oval, lenticular, [Page 218] conical, spiral, snake-like, looped, and nameless. Compare the sprays of theCrab nebulæ above z Tauri, seen in Fig. 79, and the ring nebula, Fig. 80. This last possibly consists of stars, and is situated, asshown in Fig. 81, midway between b and g Lyræ. [Illustration: Fig. 78. --The great Nebula about the multiple Starth Orionis. (See Frontispiece. )] When Herschel was sweeping the heavens with his telescope, andsaw but few stars, he often said to his assistant, "Prepare towrite; the nebulæ are coming. " They are most abundant where thestars are least so. A zone about the heavens 30° wide, with theMilky Way in the centre, would include one-fourth of the celestialsphere; but instead of one-fourth, we find nine-tenths[Page 219]of the stars in this zone, and but one-tenth of the nebulæ. These immense masses of unorganized matter are noticed to changetheir forms, vary their light greatly, but not quickly; they changethrough the ages. "God works slowly. " He takes a thousand yearsto lift his hand off. [Illustration: Fig. 79. --Crab Nebula, near z Tauri. (See Frontispiece. )] There are many unsolved problems connected with these strange bodies. Whether they belong to our system, or are beyond it, is not settled;the weight of evidence leans to the first view. [Page 220]_Variable Stars. _ [Illustration: Fig. 80. --The Ring Nebula. ] Our sun gives a variable amount of light, changing through a periodof eleven years. Probably every star, if examined by methodssufficiently delicate and exact, would be found to be variable. The variations of some [Page 221] stars are so marked as tochallenge investigation. B Lyræ (Fig. 81) has two maxima and minimaof light. In three days it rises from magnitude 4-1/2 to 3-1/2; in aweek falls to 4, and rises to 3-1/2; and in three days more drops to4-1/2: it makes all these changes in thirteen days; but this periodis constantly increasing. The variations of one hundred andforty-three stars have been well ascertained. [Illustration: Fig. 81. --Constellation Lyra, showing place of theRing Nebula. ] Mira, or the Wonderful, in the Whale (Fig. 68), is easily found whenvisible. Align from Capella to the Pleiades, and as much farther, and four stars will be seen, situated thus: * * * * The right-hand one is Mira. For half a month it shines as a starof the second magnitude. Then for three months it fades away, andlost to sight; going down even to the eleventh magnitude. But afterfive months its resurrection morning mes; and in three monthsmore--eleven months in all--our Wonderful is in its full gloryin the heavens. It its period and brilliancy are also variable. The star Megrez, d in the Great Bear, has been growing dim [Page222] for a century. In 1836 Betelguese was exceedingly variable, andcontinued so till 1840, when the changes became much lessconspicuous. Algol (Fig. 68) has been already referred to. Thisslowly winking eye is of the second magnitude during 2d. 14h. Thenit dozes off toward sleep for 4h. 24m. , when it is nearly invisible. It wakes up during the same time; so that its period from maximumbrilliancy to the same state again is 2d. 20h. 48m. Its recognizablechanges are within five or six hours. As I write, March 25th, 1879, Algol gives its minimum light at 9h. 36m. P. M. It passes fifteenminima in 43d. 13m. There will therefore be another minimum May 7th, at 9h. 49m. Its future periods are easy to estimate. Perhaps it hassome dark body revolving about it at frightful speed, in a period ofless than three days. The period of its variability is growingshorter at an increasing rate. If its variability is caused by adark body revolving about it, the orbit of that body is contracting, and the huge satellite will soon, as celestial periods are reckoned, commence to graze the surface of the sun itself, rebound again andagain, and at length plunge itself into the central fire. Such anevent would evolve heat enough to make Algol flame up into a star ofthe first magnitude, and perhaps out-blaze Sirius or Capella in ourwinter sky. None of the causes for these changes we have been able to conjectureseem very satisfactory. The stars may have opaque planets revolvingabout them, shutting off their light; they may rotate, and haveunequally illuminated sides; they may revolve in very ellipticalorbits, so as to greatly alter their distance from us; they maybe so situated in regard to zones of meteorites as [Page 223] tocall down periodically vast showers; but none or all of thesesuppositions apply to all cases, if they do to any. _Temporary, New, and Lost Stars. _ Besides regular movements to right and left, up and down, to andfrom us--changes in the intensity of illumination by changes ofdistance--besides variations occurring at regular and ascertainableintervals, there are stars called _temporary_, shining awhile andthen disappearing; _new_, coming to a definite brightness, and soremaining; and _lost_, those whose first appearance was not observed, but which have utterly disappeared. In November, 1572, a new star blazed out in Cassiopeia. Its placeis shown in Fig. 67, ch g being the stars d * g ch in the seat of the chair, and d being the first one in the back. This star was visible at noonday, and was brighter than any otherstar in the heavens. In January, 1573, it was less bright thanJupiter; in April it was below the second magnitude, and the lastof May it utterly disappeared. It was as variable in color as inbrilliancy. During its first two months, the period of greatestbrightness, it was dazzling white, then became yellow, and finallyas red as Mars or Aldebaran, and so expired. A bright star was seen very near to the place of the _Pilgrim_, as the star of 1572 was called, in A. D. 945 and 1264. A star ofthe tenth magnitude is now seen brightening slowly almost exactlyin the same place. It is possible that this is a variable starof a period of about three hundred and ten years, and will blazeout again about 1885. But we have had, within a few years, fine opportunities [Page 224]to study, with improved instruments, two new stars; On the eveningof May 12th, 1866, a star of the second magnitude was observed inthe Northern Crown, where no star above the fifth magnitude had beentwenty-four hours before. In Argelander's chart a star of the tenthmagnitude occupies the place. May 13th it had declined to the thirdmagnitude, May 16th to the fourth, May 17th to the fifth, May 19thto the seventh, May 31st to the ninth, and has since diminished tothe tenth. The spectroscope showed it to be a star in the usualcondition; but through the usual colored spectrum, crossed withbright lines, shone four bright lines, two of which indicatedglowing hydrogen. Here was plenty of proof that an unusual amount ofthis gas had given this sun its sudden flame. As the hydrogen burnedout the star grew dim. Two theories immediately presented themselves: First, that vastvolumes had been liberated from within the orb by some sudden breakingup of the doors of its great deeps; or, second, this star hadprecipitated upon itself, by attraction, some other sun or planet, the force of whose impact had been changed into heat. Though we see the liberated hydrogen of our sun burst up with suddenflame, it can hardly be supposed that enough could be liberatedat once to increase the light and heat one hundred-fold. In regard to the second theory, it is capable of proof that twosuns half as large as ours, moving at a velocity of four hundredand seventy-six miles per second, would evolve heat enough to supplythe radiation of our sun for fifty million years. How could it bepossible for a sun like this newly blazing orb to cool off to such a[Page 225] degree in a month? Besides, there would not be one chancein a thousand for two orbs to come directly together. They wouldrevolve about each other till a kind of grazing contact of grindingworlds would slowly kindle the ultimate heat. It is far more likely that this star encountered an enormous streamof meteoric bodies, or perhaps absorbed a whole comet, that laidits million leagues of tail as fuel on the central fire. Only letit be remembered that the fuel is far more force than substance. Allusion has already been made to the sudden brightening of oursun on the first day of September, 1859. That was caused, no doubt, by the fall of large meteors, following in the train of the cometof 1843, or some other comet. What the effect would have been, hadthe whole mass of the comet been absorbed, cannot be imagined. Another new star lately appeared in Cygnus, near the famous star61--the first star in the northern hemisphere whose distance wasdetermined. It was first seen November 24th, 1876, as a third magnitudestar of a yellow color. By December 2d it had sunk to the fourthmagnitude, and changed to a greenish color. It had then three brighthydrogen lines, the strong double sodium line, and others, whichmade, it strongly resemble the spectrum of the chromosphere of oursun. An entirely different result appeared in the fading of thesetwo stars. In the case of the star in the Crown, the extraordinarylight was the first to fade, leaving the usual stellar spectrum. Inthe case of the star in Cygnus, the part of the spectrum belongingto stellar light was the first to fade, leaving the bright lines;that is, the gas of one gave way to regular starlight, and thestarlight [Page 226] of the other having faded, the regular light ofthe glowing gas continued. By some strange oversight, no one studiedthe star again for six months. In September and November, 1877, thelight of this star was found to be blue, and not to be starlight atall. It had no rainbow spectrum, only one kind of rays, and henceonly one color. Its sole spectroscopic line is believed to be thatof glowing nitrogen gas. We have then, probably, in the star of1876, a body shining by a feeble and undiscernible light, surroundedby a discernible immensity of light of nitrogen gas. This is itsusual condition; but if a flight of meteors should raise the heat ofthe central body so as to outshine the nebulous envelope, we shouldhave the conditions we discovered in November, 1876. But a rapidcooling dissipates the observable light of all colors, and leavesonly the glowing gas of one color. _Movements of Stars. _ We call the stars _fixed_, but motion and life are necessary to allthings. Besides the motion in the line of sight described already, there is motion in every other conceivable direction. We knew Siriusmoved before we had found the cause. We know that our sun movesback and forth in his easy bed one-half his vast diameter, as thelarger planets combine their influence on one side or the other. The sun has another movement. We find the stars in Hercules graduallyspreading from each other. Hercules's brawny limbs grow brawnierevery century. There can be but one cause: we are approaching thatquarter of the heavens. (See [Symbol], Fig. 72. ) We are even [Page227] able to compute the velocity of our approach; it is four milesa second. The stars in the opposite quarter of the heavens in Argoare drawing nearer together. This movement would have no effect on the apparent place of thestars at either pole, if they were all equally distant; but itmust greatly extend or contract the apparent space between them, since they are situated at various distances. Independent of this, the stars themselves are all in motion, but sovast is the distance from which we observe them that it has takenan accumulation of centuries before they could be made measurable. A train going forty miles an hour, seen from a distance of twomiles, almost seems to stand still. Arcturus moves through spacethree times as fast as the earth, but it takes a century to appearto move the eighth part of the diameter of the moon. There is astar in the Hunting Dogs, known as 1830 Groombridge, which has avelocity beyond what all the attraction of the matter of the knownuniverse could give it. By the year 9000 it may be in Berenice'sHair. Some stars have a common movement, being evidently related together. A large proportion of the brighter stars between Aldebaran andthe Pleiades have a common motion eastward of about ten secondsa century. All the angles marked by a, b, g, ch Orionis will bealtered in different directions; l is moving toward g. L and ewill appear as a double star. In A. D. 50, 000 Procyon will be nearerch Orionis than Rigel now is, and Sirius will be in line with a andch Orionis. All the stars of the Great Dipper, except Benetnaschand Dubhe, have a common motion somewhat in the direction [Page 228]of Thuban (Fig. 67), while the two named have a motion nearlyopposite. In 36, 000 years the end of the Dipper will have fallen outso that it will hold no water, and the handle will be broken squareoff at Mizar. "The Southern Cross, " says Humboldt, "will not alwayskeep its characteristic form, for its four stars travel in differentdirections with unequal velocities. At the present time it is notknown how many myriads of years must elapse before its entiredislocation. " These movements are not in fortuitous or chaotic ways, but aredoubtless in accordance with some perfect plan. We have climbedup from revolving earth and moon to revolving planets and sun, in order to understand how two or ten suns can revolve about acommon centre. Let us now leap to the grander idea that all theinnumerable stars of a winter night not only loan, but must revolveabout some centre of gravity. Men have been looking for a centralsun of suns, and have not found it. None is needed. Two suns canbalance about a point; all suns can swing about a common centre. That one unmoving centre may be that city more gorgeous than Easternimagination ever conceived, whose pavement is transparent gold, whose walls are precious stones, whose light is life, and whereno dark planetary bodies ever cast shadows. There reigns the Kingand Lord of all, and ranged about are the far-off provinces of hismaterial systems. They all move in his sight, and receive powerfrom a mind that never wearies. [Page 229]XI. THE WORLDS AND THE WORD. "The worlds were framed by the word of God. "--_Heb. _ xi. , 3. [Page 230] "Mysterious night! when our first parent knew thee From report divine, and heard thy name, Did he not tremble for this lovely frame, This glorious canopy of light and blue? Yet, 'neath a curtain of translucent dew, Bathed in the rays of the great setting flame, Hesperus, with all the host of heaven, came, And lo! creation widened in man's view. Who could have thought such darkness lay concealed Within thy beams, O Sun! Oh who could find, Whilst fruit and leaf and insect stood revealed, That to such countless worlds thou mad'st us blind! Why do we then shun death with anxious strife? If light conceal so much, wherefore not life?" BLANCO WHITE. [Page 231]XI. _THE WORLDS AND THE WORD. _ Men have found the various worlds to be far richer than they originallythought. They have opened door after door in their vast treasuries, have ascended throne after throne of power, and ruled realms ofincreasing extent. We have no doubt that unfoldings in the futurewill amaze even those whose expectations have been quickened bythe revealings of the past. What if it be found that the Word isequally inexhaustible? After ages of thought and discovery we have come out of the darknessand misconceptions of men. We believe in no serpent, turtle, orelephant supporting the world; no Atlas holding up the heavens;no crystal domes, "with cycles and epicycles scribbled o'er. " Whatif it be found that one book, written by ignorant men, never fellinto these mistakes of the wisest! Nay, more, what if some of thegreatest triumphs of modern science are to be found plainly statedin a book older than the writings of Homer? If suns, planets, andsatellites, with all their possibilities of life, changes of floraand fauna, could be all provided for, as some scientists tell us, in the fiery star-dust of a cloud, why may not the same Authorprovide a perpetually widening river of life in his Word? As webelieve He is perpetually present in his worlds, we know He has[Page 232] promised to be perpetually present in his Word, making italive with spirit and life. The wise men of the past could not avoid alluding to ideas the falsityof which subsequent discovery has revealed; but the writers of theBible did avoid such erroneous allusion. Of course they referredto some things, as sunrise and sunset, according to appearance;but our most scientific books do the same to-day. That the Biblecould avoid teaching the opposite of scientific truth proclaimsthat a higher than human wisdom was in its teaching. That negative argument is strong, but the affirmative argument ismuch stronger. The Bible declares scientific truth far in advanceof its discovery, far in advance of man's ability to understandits plain declarations. Take a few conspicuous illustrations: The Bible asserted from the first that the present order of thingshad a beginning. After ages of investigation, after researches inthe realms of physics, arguments in metaphysics, and conclusionsby the necessities of resistless logic, science has reached thesame result. The Bible asserted from the first that creation of matter precededarrangement. It was chaos--void--without form--darkness; arrangementwas a subsequent work. The world was not created in the form itwas to have; it was to be moulded, shaped, stratified, coaled, mountained, valleyed, subsequently. All of which science uttersages afterward. The Bible did not hesitate to affirm that light existed beforethe sun, though men did not believe it, and used it as a weaponagainst inspiration. Now we praise men for having demonstratedthe oldest record. [Page 233]It is a recently discovered truth of science that the trata ofthe earth were formed by the action of water, and the mountainswere once under the ocean. It is an idea long familiar to Biblereaders: "Thou coverest the earth with the deep as with a garment. The waters stood above the mountains. At thy rebuke they fled; atthe voice of thy thunder they hasted away. The mountains ascend;the valleys descend into the place thou hast founded for them. "Here is a whole volume of geology in a paragraph. The thunder ofcontinental convulsions is God's voice; the mountains rise by God'spower; the waters haste away unto the place God prepared for them. Our slowness of geological discovery is perfectly accounted for byPeter. "For of this they are _willingly ignorant_, that by the wordof God there were heavens of old, and land framed out of water, andby means of water, whereby the world that then was, being overflowedby water, perished. " We recognize these geological subsidences, but we read them from the testimony of the rocks more willinglythan from the testimony of the Word. Science exults in having discovered what it is pleased to call anorder of development on earth--tender grass, herb, tree; movingcreatures that have life in the waters; bird, reptile, beast, cattle, man. The Bible gives the same order ages before, and calls it God'ssuccessive creations. During ages on ages man's wisdom held the earth to be flat. Meanwhile, God was saying, century after century, of himself, "He sitteth uponthe sphere of the earth" (Gesenius). Men racked their feeble wits for expedients to uphold [Page 234] theearth, and the best they could devise were serpents, elephants, andturtles; beyond that no one had ever gone to see what supportedthem. Meanwhile, God was perpetually telling men that he had hungthe earth upon nothing. Men were ever trying to number the stars. Hipparchus counted onethousand and twenty-two; Ptolemy one thousand and twenty-six; andit is easy to number those visible to the naked eye. But the Biblesaid, when there were no telescopes to make it known, that theywere as the sands of the sea, "innumerable. " Science has appliancesof enumeration unknown to other ages, but the space-penetratingtelescopes and tastimeters reveal more worlds--eighteen millionsin a single system, and systems beyond count--till men acknowledgethat the stars are innumerable to man. It is God's prerogative "tonumber all the stars; he also calleth them all by their names. " Torricelli's discovery that the air had weight was received withincredulity. For ages the air had propelled ships, thrust itselfagainst the bodies of men, and overturned their works. But no manever dreamed that weight was necessary to give momentum. Duringall the centuries it had stood in the Bible, waiting for man'scomprehension: "He gave to the air its weight" (Job xxviii. 25). The pet science of to-day is meteorology. The fluctuations andvariations of the weather have hitherto baffled all attempts atunravelling them. It has seemed that there was no law in theirfickle changes. But at length perseverance and skill have triumphed, and a single man in one place predicts the weather and winds [Page235] for a continent. But the Bible has always insisted that thewhole department was under law; nay, it laid down that law soclearly, that if men had been willing to learn from it they mighthave reached this wisdom ages ago. The whole moral law is not moreclearly crystallized in "Thou shalt love the Lord thy God with allthy heart, and thy neighbor as thyself, " than all the fundamentalsof the science of meteorology are crystallized in these words: "Thewind goeth toward the south (equator), and turneth about (up) untothe north; it whirleth about continually, and the wind returnethagain according to his circuits (established routes). All the riversrun into the sea; yet the sea is not full: unto the place fromwhence the rivers come, thither they return again" (Eccles. I. 6, 7). Those scientific queries which God propounded to Job were unanswerablethen; most of them are so now. "Whereon are the sockets of theearth made to sink?" Job never knew the earth turned in sockets;much less could he tell where they were fixed. God answered thisquestion elsewhere. "He stretcheth the north (one socket) overthe empty place, and hangeth the earth upon nothing. " Speakingof the day-spring, God says the earth is _turned_ to it, as clayto the seal. The earth's axial revolution is clearly recognized. Copernicus declared it early; God earlier. No man yet understands the balancing of the clouds, nor the suspensionof the frozen masses of hail, any more than Job did. Had God asked if he had perceived the _length_ of the earth, manya man to-day could have answered yes. But the eternal ice keepsus from perceiving the _breadth_ [Page 236] of the earth, and showsthe discriminating wisdom of the question. The statement that the sun's going is from the end of the heaven, and his circuit to the ends of it, has given edge to many a sneerat its supposed assertion that the sun went round the earth. Itteaches a higher truth--that the sun itself obeys the law it enforceson the planets, and flies in an orbit of its own, from one end ofheaven in Argo to the other in Hercules. So eminent an astronomer and so true a Christian as General Mitchell, who understood the voices in which the heavens declare the glory ofGod, who read with delight the Word of God em bodied in worlds, andwho fed upon the written Word of God as his daily bread, declared, "We find an aptness and propriety in all these astronomicalillustrations, which are not weakened, but amazingly strengthened, when viewed in the clear light of our present knowledge. " Herschelsays, "All human discoveries seem to be made only for the purposeof confirming more strongly the truths that come from on high, andare contained in the sacred writings. " The common authorship ofthe worlds and the Word becomes apparent; their common unexplorablewealth is a necessary conclusion. Since the opening revelations of the past show an unsearchablewisdom in the Word, has that Word any prophecy concerning mysteriesnot yet understood, and events yet in the future? There are certainproblems as yet insolvable. We have grasped many clews, and followedthem far into labyrinths of darkness, but not yet through intolight. We ask in vain, "What is matter?" No man can [Page 237] answer. Wetrace it up through the worlds, till its increasing fineness, itsgrowing power, and possible identity of substance, seem as if thenext step would reveal its spirit origin. What we but hesitatinglystammer, the Word boldly asserts. We ask, "What is force?" No man can answer. We recognize its variousgrades, each subordinate to the higher--cohesion dissolvable byheat; the affinity of oxygen and hydrogen in water overcome bythe piercing intensity of electric fire; rivers seeking the seaby gravitation carried back by the sun; rock turned to soil, soilto flowers; and all the forces in nature measurably subservient tomind. Hence we partly understand what the Word has always taughtus, that all lower forces must be subject to that which is highest. How easily can seas be divided, iron made to swim, water to burn, and a dead body to live again, if the highest force exert itselfover forces made to be mastered. When we have followed force toits highest place, we always find ourselves considering the forcesof mind and spirit, and say, in the words of the Scriptures, "Godis spirit. " We ask in vain what is the end of the present condition of things. We have read the history of our globe with great difficulty--itsprophecy is still more difficult. We have asked whether the starsform a system, and if so, whether that system is permanent. Weare not able to answer yet. We have said that the sun would intime become as icy cold and dead as the moon, and then the earthwould wander darkling in the voids of space. But the end of theearth, as prophesied in the Word, is different: "The heavens willpass away with [Page 238] a rushing noise, and the elements will bedissolved with burning heat, and the earth and the works thereinwill be burned up. " The latest conclusions of science point the sameway. The great zones of uncondensed matter about the sun seem toconstitute a resisting medium as far as they reach. Encke's comet, whose orbit comes near the sun, is delayed. This gives gravitationan overwhelming power, and hence the orbit is lessened and arevolution accomplished more quickly. Faye's comet, which wheelsbeyond the track of Mars, is not retarded. If the earth movesthrough a resisting substance, its ultimate fall into the sun iscertain. Whether in that far future the sun shall have cooled off, or will be still as hot as to-day, Peter's description wouldadmirably portray the result of the impact. Peters description, however, seems rather to indicate an interference of Divine power atan appropriate time before a running down of the system at presentin existence, and a re-endowment of matter with new capabilities. After thousands of years, science discovered the true way to knowledge. It is the Baconian way of experiment, of trial, of examining theactual, instead of imagining the ideal. It is the acceptance of theScriptural plan. "If a man wills to do God's will, he shall know. "Oh taste and see! In science men try hypotheses, think the best theycan, plan broadly as possible, and then see if facts sustain thetheory. They have adopted the Scriptural idea of accepting a plan, and then working in faith, in order to acquire knowledge. Fortunately, in the work of salvation the plan is always perfect. But, in orderto make the trial under the most favorable circumstances, theremust be faith. The faith of [Page 239] science is amazing; itsassertions of the supersensual are astounding. It affirms a thousandthings that cannot be physically demonstrated: that the flight of arifle-ball is parabolic; that the earth has poles; that gages aremade of particles; that there are atoms; that an electric lightgives ten times as many rays as are visible; that there are soundsto which we are deaf, sights to which we are blind; that a thousandobjects and activities are about us, for the perception of which weneed a hundred senses instead of five. These faiths have nearly allled to sight; they have been rewarded, and the world's wealth ofknowledge is the result. The Word has ever asserted thesupersensuous, solicited man's faith, and ever uplifted every truefaith into sight. Lowell is partly right when he sings: "Science was Faith once; Faith were science now, Would she but lay her bow and arrows by, And aim her with the weapons of the time. " Faith laid her bow and arrows by before men in pursuit of worldlyknowledge discovered theirs. What becomes of the force of the sun that is being spent to-day?It is one of the firmest rocks of science that there can be noabsolute destruction of force. It is all conserved somehow. Buthow? The sun contracts, light results, and leaps swiftly into allencircling space. It can never be returned. Heat from stars invisibleby the largest telescope enters the tastimeter, and declares thatthat force has journeyed from its source through incalculable years. There is no encircling dome to reflect all this force back uponits sources. Is it lost? Science, in defence of its own dogma, should [Page 240] assign light a work as it flies in the space whichwe have learned cannot be empty. There ought to be a realm wherelight's inconceivable energy is utilized in building a granderuniverse, where there is no night. Christ said, as he went out ofthe seen into the unseen, "I go to prepare a place for you;" andwhen John saw it in vision the sun had disappeared, the moon wasgone, but the light still continued. Science finds matter to be capable of unknown refinement; waterbecomes steam full of amazing capabilities: we add more heat, superheatthe steam, and it takes on new aptitudes and uncontrollable energy. Zinc burned in acid becomes electricity, which enters iron as a kindof soul, to fill all that body with life. All matter is capableof transformation, if not transfiguration, till it shines by thelight of an indwelling spirit. Scripture readers know that bodiesand even garments can be transfigured, be made astrapton (Luke xxiv. 4), shining with an inner light. They also look for new heavens anda new earth endowed with higher powers, fit for perfect beings. When God made matter, so far as our thought permits us to know, he simply made force stationary and unconscious. Thereafter hemoves through it with his own will. He can at any time change theseforces, making air solid, water and rock gaseous, a world a cloud, or a fire-mist a stone. He may at some time restore all force toconsciousness again, and make every part of the universe thrillwith responsive joy. "Then shall the mountains and the hills breakforth before you into singing, and all the trees of the field claptheir hands. " One of these changes is to come to the earth. [Page241] Amidst great noise the heaven shall flee, the earth be burnedup, and all their forces be changed to new forms. Perhaps it willnot then be visible to mortal eyes. Perhaps force will then be madeconscious, and the flowers thereafter return our love as much aslower creatures do now. A river and tree of life may be consciouslyalive, as well as give life. Poets that are nearest to God areconstantly hearing the sweet voices of responsive feeling in nature. "For his gayer hours She has a voice of gladness and a smile, And eloquence of beauty; and she glides Into his darker musings with a mild And gentle sympathy, that steals away Their sharpness ere he is aware. " Prophets who utter God's voice of truth say, "The wilderness andthe solitary place shall be glad for holy men, and the desert shallrejoice and blossom as the rose. It shall blossom abundantly andrejoice, even with joy and singing. " Distinguish clearly between certainty and surmise. The certainty isthat the world will pass through catastrophic changes to a perfectworld. The grave of uniformitarianism is already covered with grass. He that creates promises to complete. The invisible, imponderable, inaudible ether is beyond our apprehension; it transmits impressions186, 000 miles a second; it is millions of times more capable andenergetic than air. What may be the bounds of its possibility nonecan imagine, for law is not abrogated nor designs disregarded aswe ascend into higher realms. Law works out more beautiful designswith more absolute certainty. Why [Page 242] should there not be afiner universe than this, and disconnected from this worldaltogether--a fit home for immortal souls? It is a necessity. God filleth all in all, is everywhere omnipotent and wise. Whyshould there be great vacuities, barren of power and its creativeoutgoings? God has fixed the stars as proofs of his agency at somepoints in space. But is it in points only? Science is proud of itsdiscovery that what men once thought to be empty space is moreintensely active than the coarser forms of matter can be. But inthe long times which are past Job glanced at earth, seas, clouds, pillars of heaven, stars, day, night, all visible things, and thenadded: "Lo! these are only the outlying borders of his works. Whata whisper of a word we hear of _Him!_ The thunder of his powerwho can comprehend?" Science discovers that man is adapted for mastery in this world. He is of the highest order of visible creatures. Neither is itpossible to imagine an order of beings generically higher to beconnected with the conditions of the material world. This wholesecret was known to the author of the oldest writing. "And Godblessed them, and God said unto them: Be fruitful, and multiply, and replenish the earth, and subdue it: and have dominion overthe fish of the sea, and over the fowl of the air, and over everyliving thing that moveth upon the earth. " The idea is never lostsight of in the sacred writings. And while every man knows he mustfail in one great contest, and yield himself to death, the laterportions of the divine Word offer him victory even here. The typicalman is commissioned to destroy even death, and make man a sharerin the victory. [Page 243] Science babbles at this great truth ofman's position like a little child; Scripture treats it with abreadth of perfect wisdom we are only beginning to grasp. Science tells us that each type is prophetic of a higher one. Thewhale has bones prophetic of a human hand. Has man reached perfection?Is there no prophecy in him? Not in his body, perhaps; but how hiswhole soul yearns for greater beauty. As soon as he has found food, the savage begins to carve his paddle, and make himself gorgeous withfeathers. How man yearns for strength, subduing animal and cosmicforces to his will! How he fights against darkness and death, andstrives for perfection and holiness! These prophecies compel us tobelieve there is a world where powers like those of electricity andluminiferous ether are ever at hand; where its waters are riversof life, and its trees full of perfect healing, and from which allunholiness is forever kept. What we infer, Scripture affirms. Science tells us there has been a survival of the fittest. Doubtlessthis is so. So in the future there will be a survival of the fittest. What is it? Wisdom, gentleness, meekness, brotherly kindness, andcharity. Over those who have these traits death hath no permanentpower. The caterpillar has no fear as he weaves his own shroud; forthere is life within fit to survive, and ere long it spreads itsgorgeous wings, and flies in the air above where once it crawled. Manhas had two states of being already. One confined, dark, peculiarlynourished, slightly conscious; then he was born into another--wide, differently nourished, and intensely [Page 244] conscious. He knowshe may be born again into a life wider yet, differently nourished, and even yet more intensely conscious. Science has no hint how along ascending series of developments crowned by man may advanceanother step, and make man isaggelos--equal to angels. But thesimplest teaching of Scripture points out a way so clear that achild need not miss the glorious consummation. When Uranus hastened in one part of its orbit, and then retarded, and swung too wide, men said there must be another attracting worldbeyond; and, looking there, Neptune was found. So, when individualmen are so strong that nations or armies cannot break down theirwills; so brave, that lions have no terrors; so holy, that temptationcannot lure nor sin defile them; so grand in thought, that mencannot follow; so pure in walk, that God walks with them--let usinfer an attracting world, high and pure and strong as heaven. Theeleventh chapter of Hebrews is a roll-call of heroes of whom thisworld was not worthy. They were tortured, not accepting deliverance, that they might obtain a better resurrection. The world to comeinfluenced, as it were, the orbits of their souls, and when theirbodies fell off, earth having no hold on them, they sped on totheir celestial home. The tendency of such souls necessitates sucha world. The worlds and the Word speak but one language, teach but one setof truths. How was it possible that the writers of the earlierScriptures described physical phenomena with wonderful sublimity, and with such penetrative truth? They gazed upon the same heaventhat those men saw who ages afterward led the world in knowledge. These latter were near-sighted, and absorbed [Page 245] in thepictures on the first veil of matter; the former were far-sighted, and penetrated a hundred strata of thickest material, and saw theimmaterial power behind. The one class studied the present, and madethe gravest mistakes; the other pierced the uncounted ages of thepast, and uttered the profoundest wisdom. There is but oneexplanation. He that planned and made the worlds inspired the Word. Science and religion are not two separate departments, they arenot even two phases of the same truth. Science has a broader realmin the unseen than in the seen, in the source of power than in theoutcomes of power, in the sublime laws of spirit than in the lawsof matter; and religion sheds its beautiful light over all stagesof life, till, whether we eat or whether we drink, or whatsoeverwe do, we may do all for the glory of God. Science and religionmake common confession that the great object of life is to learnand to grow. Both will come to see the best possible means, forthe attainment of this end is a personal relation to a teacherwho is the Way, the Truth, and the Life. [Page 247]XII. THE ULTIMATE FORCE. "In the beginning was the Word, and the Word was with God, and theWord was God. The same was in the beginning with God. All thingsbecame by him, and without him was not anything made that was made* * * and by him all things stand together. " [Page 248] "O thou eternal one; whose presence blight All space doth occupy--all motion guide-- Thou from primeval nothingness didst call First chaos, then existence. Lord, on thee Eternity had its foundation: all Sprung forth from thee--of light, joy, harmony, Sole origin: all life, all beauty thine. Thy word created all, and doth create; Thy splendor fills all space with rays divine; Thou art and wert, and shalt be glorious, great; Life-giving, life-sustaining Potentate, Thy chains the unmeasured universe surround-- Upheld by thee, by thee inspired with breath. " DERZHAVIN. [Page 249]XII. _THE ULTIMATE FORCE. _ The universe is God's name writ large. Thought goes up the shiningsuns as golden stairs, and reads the consecutive syllables--allmight, and wisdom, and beauty; and if the heart be fine enough andpure enough, it also reads everywhere the mystic name of love. Letus learn to read the hieroglyphics, and then turn to the blazonryof the infinite page. That is the key-note; the heavens and the earthdeclaring the glory of God, and men with souls attuned listening. To what voices shall we listen first? Stand on the shore of a lakeset like an azure gem among the bosses of green hills. The patterof rain means an annual fall of four cubic feet of water on everysquare foot of it. It weighs two hundred and forty pounds to thecubic foot, one hundred million tons on the surface of a littlesheet of water twenty miles long by three wide. Now, all that weightof falling rain had to be lifted, a work compared to which takingup mountains and casting them into the sea is pastime. All thatwater had to be taken up before it could be cast down, and carriedhundreds of miles before it could be there. You have heard Niagara'sthunder; have stood beneath the falling immensity; seen it ceaselesslypoured from an infinite hand; felt that you would be ground to atomsif you fell into that resistless flood. Well, all that infinity of[Page 250] water had to be lifted by main force, had to be taken upout of the far Pacific, brought over the Rocky Mountains; and theMississippi keeps bearing its wide miles of water to the Gulf, andNiagara keeps thundering age after age, because there is powersomewhere to carry the immeasurable floods all the time the otherway in the upper air. But this is only the Alpha of power. Professor Clark, of Amherst, Massachusetts, found that such a soft and pulpy thing as a squashhad so great a power of growth that it lifted three thousand pounds, and held it day and night for months. It toiled and grew under thegrowing weight, compacting its substance like oak to do the work. All over the earth this tremendous power and push of life goeson--in the little star-eyed flowers that look up to God only onthe Alpine heights, in every tuft of grass, in every acre of wheat, in every mile of prairie, and in every lofty tree that wrestleswith the tempests of one hundred winters. But this is only the Bin the alphabet of power. Rise above the earth, and you find the worlds tossed like playthings, and hurled seventy times as fast as a rifle-ball, never an inchout of place or a second out of time. But this is only the C inthe alphabet of power. Rise to the sun. It is a quenchless reservoir of high-class energy. Our tornadoes move sixty miles an hour, those of the sun twentythousand miles an hour. A forest on fire sends its spires of flameone hundred feet in air, the sun sends its spires of flame twohundred thousand miles. All our fires exhaust the fuel and burnout. If the sun were pure coal, it would burn out in five thousandyears; and yet this sea of unquenchable [Page 251] flame seethes andburns, and rolls and vivifies a dozen worlds, and flashes life alongthe starry spaces for a million years without any apparentdiminution. It sends out its power to every planet, in the vastcircle in which it lies. It fills with light not merely a wholecircle, but a dome; not merely a dome above, but one below, and onevery side. At our distance of ninety-two and a half millions ofmiles, the great earth feels that power in gravitation, tides, rains, winds, and all possible life--every part is full of power. Fill the earth's orbit with a circle of such receptiveworlds--seventy thousand instead of one--everyone would be as fullysupplied with power from this central source. More. Fill the wholedome, the entire extent of the surrounding sphere, bottom, sides, top, a sphere one hundred and eighty-five million miles in diameter, and everyone of these uncountable worlds would be touched with thesame power as one; each would thrill with life. This is only the Dof the alphabet of power. And glancing up to the other suns, onehundred, five hundred, twelve hundred times as large, double, triple, septuple, multiple suns, we shall find power enough to gothrough the whole alphabet in geometrical ratio; and then in theclustered suns, galaxies, and nebulæ, power enough stillunrepresented by single letters to require all combinations of thealphabet of power. What is the significance of this single elementof power? The answer of science to-day is "correlation, " theconstant evolution of one force from another. Heat is a mode ofmotion, motion a result of heat. So far so good. But are we merereasoners in a circle? Then we would be lost men, treading our roundof death in a limitless forest. What is the ultimate? Reason [Page252] out in a straight line. No definition of matter allows it tooriginate force; only mind can do that. Hence the ultimate force isalways mind. Carry your correlation as far as you please--throughplanets, suns, nebulæ, concretionary vortices, and revolvingfire-mist--there must always be mind and will beyond. Some of thatwillpower that works without exhaustion must take its own force andrender it static, apparent. It may do this in such correlatedrelation that that force shall go on year after year to a thousandchanging forms; but that force must originate in mind. Go out in the falling rain, stand under the thunderous Niagara, feel the immeasurable rush of life, see the hanging worlds, andtrace all this--the carried rain, the terrific thunder with God's bowof peace upon it, and the unfailing planets hung upon nothing--traceall this to the orb of day blazing in perpetual strength, but stopnot there. Who _made_ the sun? Contrivance fills all thought. _Who_made the sun? Nature says there is a mind, and that mind is Almighty. Then you have read the first syllables, viz. , being and power. What is the continuous relation of the universe to the mind fromwhich it derived its power? Some say that it is the relation ofa wound-up watch to the winder. It was dowered with sufficientpower to revolve its ceaseless changes, and its maker is henceforthan absentee God. Is it? Let us have courage to see. For twentyyears one devotes ten seconds every night to putting a little forceinto a watch. It is so arranged that it distributes that forceover twenty-four hours. In that twenty years more power has beenput into that watch than a horse could exert at once. But suppose[Page 253] one had tried to put all that force into the watch atonce: it would have pulverized it to atoms. But supposing theuniverse had been dowered with power at first to run its enormousrounds for twenty millions of years. It is inconceivable; steelwould be as friable as sand, and strengthless as smoke, in suchstrain. We have discovered some of the laws of the force we call gravitation. But what do we know of its essence? How it appears to act we know alittle, what it is we are profoundly ignorant. Few men ever discussthis question. All theories are sublimely ridiculous, and fail topass the most primary tests. How matter can act where it is not, and on that with which it has no connection, is inconceivable. Newton said that anyone who has in philosophical matters a competentfaculty of thinking, could not admit for a moment the possibilityof a sun reaching through millions of miles, and exercising therean attractive power. A watch may run if wound up, but how thewatch-spring in one pocket can run the watch in another is hardto see. A watch is a contrivance for distributing a force outsideof itself, and if the universe runs at all on that principle, itdistributes some force outside of itself. Le Sage's theory of gravitation by the infinitive hail of atomscannot stand a minute, hence we come back as a necessity of thoughtto Herschel's statement. "It is but reasonable to regard gravityas a result of a consciousness and a will existent somewhere. "Where? I read an old book speaking of these matters, and it saysof God, He hangeth the earth upon nothing; he upholdeth constantlyall things by the word of his power. [Page 254] By him all thingsconsist or hold together. It teaches an imminent mind; an almighty, constantly exerted power. Proof of this starts up on every side. There is a recognized tendency in all high-class energy todeteriorate to a lower class. There is steam in the boiler, but itwastes without fuel. There is electricity in the jar, but everyparticle of air steals away a little, unless our conscious force isexerted to regather it. There is light in the sun, but infinitespace waits to receive it, and takes it swift as light can leap. Wesaid that if the sun were pure coal, it would burn out in fivethousand years, but it blazes undimmed by the million. How can it?There have been various theories: chemical combustion, it hasfailed; meteoric impact, it is insufficient; condensation, it is notproved; and if it were, it is an intermediate step back to theoriginal cause of condensation. The far-seeing eyes see in the sunthe present active power of Him who first said, "Let there belight, " and who at any moment can meet a Saul in the way to Damascuswith a light above the brightness of the sun--another noon arisen onmid-day; and of whom it shall be said in the eternal state ofunclouded brightness, where sun and moon are no more, "The glory ofthe Lord shall lighten it, and the Lamb is the light thereof. " But suppose matter could be dowered, that worlds could have agravitation, one of two things must follow: It must have consciousknowledge of the position, exact weight, and distance of everyatom, mass, and world, in order to proportion the exact amount ofgravity, or it must fill infinity with an omnipresent attractivepower, pulling in myriads of places at nothing; in [Page 255] a fewplaces at worlds. Every world must exert an infinitely extendedpower, but myriads of infinities cannot be in the same space. Thesolution is, one infinite power and conscious will. To see the impossibility of every other solution, join in the longand microscopic hunt for the ultimate particle, the atom; and iffound, or if not found, to a consideration of its remarkable powers. Bring telescopes and microscopes, use all strategy, for that atomis difficult to catch. Make the first search with the microscope:we can count 112, 000 lines ruled on a glass plate inside of aninch. But we are here looking at mountain ridges and valleys, notatoms. Gold can be beaten to the 1/340000 of an inch. It can bedrawn as the coating of a wire a thousand times thinner, to the1/340000000 of an inch. But the atoms are still heaped one uponanother. Take some of the infusorial animals. Alonzo Gray says millionsof them would not equal in bulk a grain of sand. Yet each of themperforms the functions of respiration, circulation, digestion, and locomotion. Some of our blood-vessels are not a millionth ofour size. What must be the size of the ultimate particles thatfreely move about to nourish an animal whose totality is too smallto estimate? A grain of musk gives off atoms enough to scent everypart of the air of a room. You detect it above, below, on everyside. Then let the zephyrs of summer and the blasts of winter sweepthrough that room for forty years, bearing out into the wide worldmiles on miles of air, all perfumed from the atoms of that grainof musk, and at the end of the forty years the weight of musk hasnot appreciably diminished. [Page 256] Yet uncountable myriads onmyriads of atoms have gone. Our atom is not found yet. Many are the ways of searching for itwhich we cannot stop to consider. We will pass in review the propertieswith which materialists preposterously endow it. It is impenetrableand indivisible, though some atoms are a hundred times larger thanothers. Each has definite shape; some one shape, and some another. They differ in weight, in quantity of combining power, in qualityof combining power. They combine with different substances, incertain exact assignable quantities. Thus one atom of hydrogencombines with eighty of bromine, one hundred and sixty of mercury, two hundred and forty of boron, three hundred and twenty of silicon, etc. Hence our atom of hydrogen must have power to count, or atleast to measure, or be cognizant of bulk. Again, atoms are ofdifferent sorts, as positive or negative to electric currents. They have power to take different shapes with different atoms incrystallization; that is, there is a power in them, conscious orotherwise, that the same bricks shall make themselves into stablesor palaces, sewers or pavements, according as the mortar varies. "No, no, " you cry out; "it is only according as the builder varieshis plan. " There is no need to rehearse these powers much further;though not one-tenth of the supposed innate properties of thisinfinitesimal infinite have been recited--properties which areexpressed by the words atomicity, quantivilence, monad, dryad, univalent, perissad, quadrivalent, and twenty other terms, eachexpressing some endowment of power in this in visible atom. Referto one more presumed ability, an ability [Page 257] to keepthemselves in exact relation of distance and power to each other, without touching. It is well known that water does not fill the space it occupies. We can put eight or ten similar bulks of different substances intoa glass of water without greatly increasing its bulk, some actuallydiminishing it. A philosopher has said that the atoms of oxygenand hydrogen are probably not nearer to each other in water thanone hundred and fifty men would be if scattered over the surfaceof England, one man to four hundred square miles. The atoms of the luminiferous ether are infinitely more diffused, and yet its interactive atoms can give four hundred millions oflight-waves a second. And now, more preposterous than all, eachatom has an attractive power for every other atom of the universe. The little mote, visible only in a sunbeam streaming through adark room, and the atom, infinitely smaller, has a grasp upon thewhole world, the far-off sun, and the stars that people infinitespace. The Sage of Concord advises you to hitch your wagon to astar. But this is hitching all stars to an infinitesimal part ofa wagon. Such an atom, so dowered, so infinite, so conscious, isan impossible conception. But if matter could be so dowered as to produce such results bymechanism, could it be dowered to produce the results of intelligence?Could it be dowered with power of choice without becoming mind?If oxygen and hydrogen could be made able to combine into water, could the same unformed matter produce in one case a plant, inanother a bird, in a third a man; and in each of these put bone, brain, blood, and nerve in [Page 258] proper relations? Matter mustbe mind, or subject to a present working mind, to do this. Theremust be a present intelligence directing the process, laying thedead bricks, marble, and wood in an intelligent order for a livingtemple. If we do put God behind a single veil in dead matter, in allliving things he must be apparent and at work. If, then, such athing as an infinite atom is impossible, shall we not bestunderstand matter by saying it is a visible representation of God'spersonal will and power, of his personal force, and perhapsknowledge, set aside a little from himself, still possessed somewhatof his personal attributes, still responsive to his will. What wecall matter may be best understood as God's force, will, knowledge, rendered apparent, static, and unweariably operative. Unless matteris eternal, which is unthinkable, there was nothing out of which theworld could be made, but God himself; and, reverently be it said, matter seems to retain fit capabilities for such source. Is not thisthe teaching of the Bible? I come to the old Book. I come to thatman who was taken up into the arcana of the third heaven, the holyof holies, and heard things impossible to word. I find he makes aclear, unequivocal statement of this truth as God's revelation tohim. "By faith, " says the author of Hebrews, "we understand theworlds were framed by the word of God, so that things which are seenwere not made of things which do appear. " In Corinthians, Paulsays--But to us there is but one God, the Father, of whom [as asource] are all things; and one Lord Jesus Christ, by whom [as acreative worker] are all things. So in Romans he says--"For out ofhim, and through him, and to him are all things, to whom be gloryforever. Amen. " [Page 259]God's intimate relation to matter is explained. No wonder the forcesrespond to his will; no wonder pantheism--the idea that matter isGod--has had such a hold upon the minds of men. Matter, derivedfrom him, bears marks of its parentage, is sustained by him, andwhen the Divine will shall draw it nearer to himself the new powerand capabilities of a new creation shall appear. Let us pay a higherrespect to the attractions and affinities; to the plan and powerof growth; to the wisdom of the ant; the geometry of the bee; themigrating instinct that rises and stretches its wings toward aprovided South--for it is all God's present wisdom and power. Letus come to that true insight of the old prophets, who are fittinglycalled seers; whose eyes pierced the veil of matter, and saw Godclothing the grass of the field, feeding the sparrows, giving snowlike wool and scattering hoar-frost like ashes, and ever standing onthe bow of our wide-sailing world, and ever saying to all tumultuousforces, "Peace, be still. " Let us, with more reverent step, walkthe leafy solitudes, and say: "Father, thy hand Hath reared these venerable columns: Thou Did'st weave this verdant roof. Thou did'st look down Upon the naked earth, and forthwise rose All these fair ranks of trees. They in Thy sun Budded, and shook their green leaves in Thy breeze. "That delicate forest flower, With scented breath and looks so like a smile, Seems, as it issues from the shapeless mould, An emanation of the indwelling life, A visible token of the unfolding love That are the soul of this wide universe. "--BRYANT. [Page 260]Philosophy has seen the vast machine of the universe, wheel withinwheel, in countless numbers and hopeless intricacy. But it hasnot had the spiritual insight of Ezekiel to see that they wereeveryone of them full of eyes--God's own emblem of the omniscientsupervision. What if there are some sounds that do not seem to be musicallyrhythmic. I have seen where an avalanche broke from the mountain sideand buried a hapless city; have seen the face of a cliff shatteredto fragments by the weight of its superincumbent mass, or piercedby the fingers of the frost and torn away. All these thunder downthe valley and are pulverized to sand. Is this music? No, but itis a tuning of instruments. The rootlets seize the sand and turnit to soil, to woody fibre, leafy verdure, blooming flowers, anddelicious fruit. This asks life to come, partake, and be made strong. The grass gives itself to all flesh, the insect grows to feed thebird, the bird to nourish the animal, the animal to develop theman. Notwithstanding the tendency of all high-class energy to deteriorate, to find equilibrium, and so be strengthless and dead, there is, somehow, in nature a tremendous push upward. Ask any philosopher, and he will tell you that the tendency of all endowed forces isto find their equilibrium and be at rest--that is, dead. He drawsa dismal picture of the time when the sun shall be burned out, and the world float like a charnel ship through the dark, coldvoids of space--the sun a burned-out char, a dead cinder, and theworld one dismal silence, cold beyond measure, and dead beyondconsciousness. The philosopher has wailed a dirge without [Page 261]hope, a requiem without grandeur, over the world's future. Butnature herself, to all ears attuned, sings pæans, and shouts to menthat the highest energy, that of life, does not deteriorate. Mere nature may deteriorate. The endowments of force must spendthemselves. Wound-up watches and worlds must run down. But naturesustained by unexpendable forces must abide. Nature filled withunexpendable forces continues in form. Nature impelled by a magnificentpush of life must ever rise. Study her history in the past. Sulphurous realms of deadly gasesbecome solid worlds; surplus sunlight becomes coal, which is reservedpower; surplus carbon becomes diamonds; sediments settle untilthe heavens are azure, the air pure, the water translucent. Ifthat is the progress of the past, why should it deteriorate in thefuture? There is a system of laws in the universe in which the higher havemastery over the lower. Lower powers are constitutionally arrangedto be overcome; higher powers are constitutionally arranged formastery. At one time the water lies in even layers near the ocean'sbed, in obedience to the law or power of gravitation. At anothertime it is heaved into mountain billows by the shoulders of thewind. Again it flies aloft in the rising mists of the morning, transfigured by a thousand rain bows by the higher powers of thesun. Again it develops the enormous force of steam by the power ofheat. Again it divides into two light flying airs by electricity. Again it stands upright as a heap by the power of some law in thespirit realm, whose mode of working we are not yet large enough[Page 262] to comprehend. The water is solid, liquid, gaseous onearth, and in air according to the grade of power operating upon it. The constant invention of man finds higher and higher powers. Oncehe throttled his game, and often perished in the desperate struggle;then he trapped it; then pierced it with the javelin; then shot itwith an arrow, or set the springy gases to hurl a rifle-ball atit. Sometime he may point at it an electric spark, and it shallbe his. Once he wearily trudged his twenty miles a day, then hetook the horse into service and made sixty; invoked the winds, and rode on their steady wings two hundred and forty; tamed thesteam, and made almost one thousand; and if he cannot yet send hisbody, he can his mind, one thousand miles a second. It all dependsupon the grade of power he uses. Now, hear the grand truth of nature:as the years progress the higher grades of power increase. Eitherby discovery or creation, there are still higher class forces tobe made available. Once there was no air, no usable electricity. There is no lack of those higher powers now. The higher we go themore of them we find. Mr. Lockyer says that the past ten years havebeen years of revelation concerning the sun. A man could not readin ten years the library of books created in that time concerningthe sun. But though we have solved certain problems and mysteries, the mysteries have increased tenfold. We do not know that any new and higher forces have been added tomatter since man's acquaintance with it. But it would be easy toadd any number of them, or change any lower into higher. That is the[Page 263] meaning of the falling granite that becomes soil, of thepulverized lava that decks the volcano's trembling sides withflowers; that is the meaning of the grass becoming flesh, and of allhigh forces constitutionally arranged for mastery over lower. Takethe ore from the mountain. It is loose, friable, worthless initself. Raise it in capacity to cast-iron, wrought-iron, steel, itbecomes a highway for the commerce of nations, over the mountainsand under them. It becomes bones, muscles, body for the inspiringsoul of steam. It holds up the airy bridge over the deep chasm. Itis obedient in your hand as blade, hammer, bar, or spring. It isinspirable by electricity, and bears human hopes, fears, and lovesin its own bosom. It has been raised from valueless ore. Change itagain to something as far above steel as that is above ore. Changeall earthly ores to highest possibility; string them to finesttissues, and the new result may fit God's hand as tools, and thrillwith his wisdom and creative processes, a body fitted for God'sspirit as well as the steel is fitted to your hand. From this worldtake opacity, gravity, darkness, bring in more mind, love, and God, and then we will have heaven. An immanent God makes a plastic world. When man shall have mastered the forces that now exist, the originalCreator and Sustainer will say, "Behold, I create all things new. "Nature shall be called nearer to God, be more full of his power. To the long-wandering Æneas, his divine mother sometimes came tocheer his heart and to direct his steps. But the goddess only showedherself divine by her departure; only when he stood in desolationdid the hero know he had [Page 264] stood face to face with divinepower, beauty, and love. Not so the Christian scholars, thewanderers in Nature's bowers to-day. In the first dawn of discovery, we see her full of beauty and strength; in closer communion, we findher full of wisdom; to our perfect knowledge, she reveals anindwelling God in her; to our ardent love, she reveals an indwellingGod in us. But the evidence of the progressive refinements of habitation is nomore clear than that of progressive refinement of the inhabitant:there must be some one to use these finer things. An empty house isnot God's ideal nor man's. The child may handle a toy, but a manmust mount a locomotive; and before there can be New Jerusalemswith golden streets, there must be men more avaricious of knowledgethan of gold, or they would dig them up; more zealous for lovethan jewels, or they would unhang the pearly gates. The upliftingrefinement of the material world has been kept back until thereshould appear masterful spirits able to handle the higher forces. Doors have opened on every side to new realms of power, when menhave been able to wield them. If men lose that ability they closeagain, and shut out the knowledge and light. Then ages, dark andfeeble, follow. Some explore prophecy for the date of the grand transformationof matter by the coming of the Son of Man, for a new creation. Alittle study of nature would show that the date cannot be fixed. A little study of Peter would show the same thing. He says, "Whatmanner of persons ought ye to be, in all holy conversation andgodliness, looking for and hastening the coming [Page 265] of theday of God, wherein the heavens being on fire shall be dissolved, and the elements shall melt with fervent heat? Nevertheless we, according to his promise, look for a new heaven and a new earth. " The idea is, that the grand transformation of matter waits thereadiness of man. The kingdom waits the king. The scattered cantonsof Italy were only prostrate provinces till Victor Emanuel came, then they were developed into united Italy. The prostrate provincesof matter are not developed until the man is victor, able to rulethere a realm equal to ten cities here. Every good man hastens thecoming of the day of God and nature's renovation. Not only doesinference teach that there must be finer men, but fact affirmsthat transformation has already taken place. Life is meant to havepower over chemical forces. It separates carbon from its compoundsand builds a tree, separates the elements and builds the body, holds them separate until life withdraws. More life means higherbeing. Certainly men can be refined and recapacitated as well asore. In Ovid's "Metamorphoses" he represents the lion in process offormation from earth, hind quarters still clay, but fore quarters, head, erect mane, and blazing eye--live lion--and pawing to getfree. We have seen winged spirits yet linked to forms of clay, but beating the celestial air, endeavoring to be free; and we haveseen them, dowered with new sight, filled with new love, breakloose and rise to higher being. In this grand apotheosis of man which nature teaches, progresslias already been made. Man has already outgrown his harmony withthe environment of mere matter. He has given his hand to science, andbeen lifted up above the earth into the voids of infinite space. He[Page 266] has gone on and on, till thought, wearied amidst theinfinities of velocity and distance, has ceased to note them. But heis not content; all his faculties are not filled. He feels that hisfuture self is in danger of not being satisfied with space, andworlds, and all mental delights, even as his manhood fails to besatisfied with the materiel toys of his babyhood. He asks for anAuthor and Maker of things, infinitely above them. He has seenwisdom unsearchable, power illimitable; but he asks for personalsympathy and love. Paul expresses his feeling: every creature--notthe whole creation--groaneth and travaileth in pain together untilnow, waiting for the adoption--the uplifting from orphanage toparentage--a translation out of darkness into the kingdom of God'sdear Son. He hears that a man in Christ is a new creation: oldthings pass away, all things become new. There is then a possibilityof finding the Author of nature, and the Father of man. He beginshis studies anew. Now he sees that all lines of knowledge convergeas they go out toward the infinite mystery; sees that theseconverging lines are the reins of government in this world; sees theconverging lines grasped by an almighty hand; sees a loving face andform behind; sees that these lines of knowledge and power are hispersonal nerves, along which flashes his will, and every force inthe universe answers like a perfect muscle. Then he asks if this Personality is as full of love as of power. He is told of a tenderness too deep for tears, a love that has theCross for its symbol, and a dying cry for its expression: seekingit, he is a new creation. He sees more wondrous things in the Wordthan in the [Page 267] world. He comes to know God with his heart, better than he knows God's works by his mind. Every song closes with the key-note with which it began, and thebrief cadence at the close hints the realms of sound through whichit has tried its wings. The brief cadence at the close is this:All force runs back into mind for its source, constant support, and uplifts into higher grades. Mr. Grove says, "Causation is the will, creation is the act, of God. "Creation is planned and inspired for the attainment of constantlyrising results. The order is chaos, light, worlds, vegetable forms, animal life, then man. There is no reason to pause here. This isnot perfection, not even perpetuity. Original plans are notaccomplished, nor original force exhausted. In another world, freefrom sickness, sorrow, pain, and death, perfection of abode isoffered. Perfection of inhabitant is necessary; and as the creativepower is everywhere present for the various uplifts and refinementsof matter, it is everywhere present with appropriate power forthe uplifting and refinement of mind and spirit. [Page 269]SUMMARY OF LATEST DISCOVERIES AND CONCLUSIONS. _Movements on the Sun. _--The discovery and measurement of the up-rush, down-rush, and whirl of currents about the sunspots, also of thedetermination of the velocity of rotation by means of the spectroscope, as described (page 53), is one of the most delicate and difficultachievements of modern science. _Movement of Stars in Line of Sight_ (page 51). --The followingtable shows this movement of stars, so far as at present known: ---------------------------------------------------------------| APROACHING. || RECEDING. ||------------------------------||-------------------------------|| Map. | Name. | Rate || Map. | Name. | Rate || | | per sec. || | | per sec. ||-------|-----------|----------||--------|-----------|----------||Fig. 71|Arcturus | 55 miles ||Fig. 69 |Sirius | 20 miles || " 72|Vega | 50 " ||Fr'piece|Betelguese | 22 " || " 73|a Cygni | 39 " || " |Rigel | 15 " || " 69|Pollux | 49 " ||Fig. 69 |Castor | 25 " || " 67|Dubhe | 46 " || " 70 |Regulus | 15 " | --------------------------------------------------------------- _Sun's Appearance. _--This was formerly supposed to be an even, regular, dazzling brightness, except where the spots appeared. But the sun's surface is now known to be mottled with what arecalled rice grains or willow leaves. But the rice grains are aslarge as the continent of America. The spaces between are calledpores. They constitute an innumerable number of small spots. Thisappearance of the general surface is well portrayed in the cuton page 92. _Close Relation between Sun and Earth. _-Men always knew that theearth received light from the sun. They subsequently discoveredthat the earth was momentarily held by the power [Page 270] ofgravitation. But it is a recent discovery that the light is one ofthe principal agents in chemical changes, in molecular grouping andworld-building, thus making all kinds of life possible (p. 30-36). The close connection of the sun and the earth will be still farthershown in the relation of sun-spots and auroras. One of the mostsignificant instances is related on page 19, when the earth felt thefall of bolides upon the sun. Members of the body no more answer tothe heart than the planets do to the sun. _Hydrogen Flames. _--It has been demonstrated that the sun flames200, 000 miles high are hydrogen in a state of flaming incandescence(page 85). _Sun's Distance. _--The former estimate, 95, 513, 794 miles, has beenreduced by nearly one-thirtieth. Lockyer has stated it as low as89, 895, 000 miles, and Proctor, in "Encyclopædia Britannica, " at91, 430, 000 miles, but discovered errors show that these estimatesare too small. Newcomb gives 92, 400, 000 as within 200, 000 milesof the correct distance. The data for a new determination of thisdistance, obtained from the transit of Venus, December 8th, 1874, have not yet been deciphered; a fact that shows the difficultyand laboriousness of the work. Meanwhile it begins to be evidentthat observations of the transit of Venus do not afford the bestbasis for the most perfect determination of the sun's distance. Since the earth's distance is our astronomical unit of measure, itfollows that all other distances will be changed, when expressedin miles, by this ascertained change of the value of the standard. _Oxygen in the Sun. _--In 1877 Professor Draper announced the discoveryof oxygen lines in the spectrum of the sun. The discovery was doubted, and the methods used were criticised by Lockyer and others, butlater and more delicate experiments substantiate Professor Draper'sclaim to the discovery. The elements known to exist in the sunare salt, iron, hydrogen, [Page 271] magnesium, barium, copper, zinc, cromium, and nickel. Some elements in the sun are scarcely, ifat all, discoverable on the earth, and some on the earth not yetdiscernible in the sun. _Substance of Stars. _--Aldebaran (_Frontispiece_) shows salt, magnesium, hydrogen, calcium, iron, bismuth, tellurium, antimony, and mercury. Some of the sun's metals do not appear. Stars differ in their verysubstance, and will, no doubt, introduce new elements to us unknownbefore. The theory that all nebulæ are very distant clusters of stars isutterly disproved by the clearest proof that some of them are onlyincandescent gases of one or two kinds. _Discoveries of New Bodies. _--Vulcan, the planet nearest the sun(page 138). The two satellites of Mars were discovered by Mr. Hall, U. S. Naval Observatory, August 11th, 1877 (page 161). "The outerone is called Diemas; the inner, Phobus. Sir William Herschel thought he discovered six satellites of Uranus. The existence of four of them has been disproved by the researches ofmen with larger telescopes. Two new ones, however, were discoveredby Mr. Lassell in 1846. _Saturn's Rings_ are proved to be in a state of fluidity and contraction(page 171). _Meteors and Comets. _--The orbits of over one hundred swarms ofmeteoric bodies are fixed: their relation to, and in some casesindentity with, comets determined. Some comets are proved to bemasses of great weight and solidity (page 133). _Aerolites. _-Some have a texture like our lowest strata of rocks. There is a geology of stars and meteors as well as of the earth. M. Meunier has just received the Lalande Medal from the Paris Academyfor his treatise showing that, so far as our present knowledge candetermine, some of these meteors once belonged to a globe developedin true geological epochs, and which has been separated into fragmentsby agencies with which we are not acquainted. [Illustration: Fig. 82. --Horizontal Pendulum. ] _The Horizontal Pendulum. _--This delicate instrument is [Page 272]represented in Fig. 82. It consists of an upright standard, stronglybraced; a weight, _m_, suspended by the hair-spring of a watch, B D, and held in a horizontal position by another watch-spring, A C. Theweight is deflected from side to side by the slightest influence. The least change in the level of a base thirty-nine inches long thatcould be detected by a spirit-level is 0". 1 of an arc--equal toraising one end 1/2068 of an inch. But the pendulum detects araising of one end 1/36000000 of an inch. To observe the movementsof the pendulum, it is kept in a dark room, and a ray of light isdirected to the mirror, _m_, and thence reflected upon a screen. Thus the least movement may be enormously magnified, and read andmeasured by the moving spot on the screen. It has been discoveredthat when the sun rises it has sufficient attraction to incline thisinstrument to the east; when it sets, to incline it to the west. Thesame is true of the moon. When either is exactly overhead orunderfoot, of course there is no deflection. The mean deflectioncaused by the moon at rising or setting is 0". 0174; by the sun, 0". 008. Great results are expected from this instrument hardly knownas yet: among others, whether gravitation acts instantly or consumestime in coming from the sun. This will be shown by the time of thechange of the pendulum from east to west when the sun reaches thezenith, and _vice versa_ when it crosses the nadir. The sun will bebest studied without light, in the quiet and darkness of some deepmine. [Page 273]_Light of Unseen Stars. _--From careful examination, it appearsthat three-fourths of the light on a fine starlight night comesfrom stars that cannot be discerned by the naked eye. The wholeamount of star light is about one-eightieth of that of the fullmoon. _Lateral Movements of Stars_, page 226-28. _Future Discoveries_--_A Trans-Neptunian Planet. _--Professor AsaphHall says: "It is known to me that at least two American astronomers, armed with powerful telescopes, have been searching quite recently fora trans-Neptunian planet. These searches have been caused by the factthat Professor Newcomb's tables of Uranus and Neptune already beginto differ from observation. But are we to infer from these errors ofthe planetary tables the existence of a trans-Neptunian planet? Itis possible that such a planet may exist, but the probability is, Ithink, that the differences are caused by errors in the theories ofthese planets. * * * A few years ago the remark was frequently madethat the labors of astronomers on the solar system were finished, andthat henceforth they could turn their whole attention to siderealastronomy. But to-day we have the lunar theory in a very discouragingcondition, and the theories of Mercury, Jupiter, Saturn, Uranus, and Neptune all in need of revision; unless, indeed, Leverrier'stheories of the last two planets shall stand the test of observation. But, after all, such a condition of things is only the naturalresult of long and accurate series of observations, which makeevident the small inequalities in the motions, and bring to lightthe errors of theory. " Future discoveries will mostly reveal the laws and conditions ofthe higher and finer forces. Already Professor Loomis telegraphstwenty miles without wire, by the electric currents between mountains. We begin to use electricity for light, and feel after it for amotor. Comets and Auroras show its presence between worlds, andin the interstellar spaces. Let another Newton arise. [Page 274] SOME ELEMENTS OF THE SOLAR SYSTEM ------------------------------------------------------------------------| | | | Mean Dist. | | || | | | from Sun. | | || | | |-------------------| Mean |Density. || | | | Earth's| |Diameter |[Earth] || Name. | Sign. | Masses. | Dist. | Millions |in Miles. | = 1. || | | | as 1. | of Miles. | | ||-----------|--------|------------|--------|----------|---------|--------|| Sun |[Symbol]| Unity | | | 860, 000 | 0. 255 || Mercury |[Symbol]|1/5000000(?)| 0. 387 | 35-3/4| 2, 992 | 1. 21 || Venus |[Symbol]| 1/425000 | 0. 723 | 66-3/4| 7, 660 | 0. 85 || Earth |[Symbol]| 1/326800 | 1. | 92-1/3| 7, 918 | 1. || Mars |[Symbol]| 1/2950000 | 1. 523 | 141 | 4, 211 | 0. 737 || Asteroids | (No. ) | | | | | || Jupiter |[Symbol]| 1/1047 | 5. 203 | 480 | 86, 000 | 0. 243 || Saturn |[Symbol]| 1/3501 | 9. 538 | 881 | 70, 500 | 0. 133 || Uranus |[Symbol]| 1/22600 | 19. 183 | 1771 | 31, 700 | 0. 226 || Neptune |[Symbol]| 1/19380 | 30. 054 | 2775 | 34, 500 | 0. 204 | ------------------------------------------------------------------------ -------------------------------------------------------------| | | Gravity | | || | Axial | at | | Orbital || | Revolu- | Surface. | Periodic | Velocity || Name. | tion | [Earth] | Time. | in Miles || | | = 1 | | per sec. ||-----------|---------------|----------|-----------|----------|| Sun | 25 to 26d | 27. 71 | | || Mercury | 24h 5m(?) | 0. 46 | 87. 97d | 29. 55 || Venus | 23h 21m(?) | 0. 82 | 224. 70d | 21. 61 || Earth | 23h 56m 4s | 1. | 365. 26d | 18. 38 || Mars | 24h 37m 22. 7s | 0. 39 | 686. 98d | 14. 99 || Asteroids | | | | || Jupiter | 9h 55m 20s | 2. 64 | 11. 86yrs | 8. 06 || Saturn | 10h 14m | 1. 18 | 29. 46yrs | 5. 95 || Uranus | Unknown. | 0. 90 | 84. 02yrs | 4. 20 || Neptune | Unknown. | 0. 89 | 164. 78yrs | 3. 36 | ------------------------------------------------------------- [Page 275] EXPLANATION OF ASTRONOMICAL SYMBOLS. SIGNS OF THE ZODIAC 0. [Symbol] Aries 0° | VI. [Symbol] Libra 180° I. [Symbol] Taurus 30 | VII. [Symbol] Scorpio 210 II. [Symbol] Gemini 60 | VIII. [Symbol] Sagittarius 240 III. [Symbol] Cancer 90 | IX. [Symbol] Capricornus 270 IV. [Symbol] Leo 120 | X. [Symbol] Aquarius 300 V. [Symbol] Virgo 150 | XI. [Symbol] Pisces 330 * * * * * [Symbol] Conjunction. | S. Seconds of Time. [Symbol] Quadrature. | ° Degrees. [Symbol] Opposition. | ' Minutes of Arc. [Symbol] Ascending Node. | " Seconds of Arc. [Symbol] Descending Node. | R. A. Right Ascension. H. Hours. | Decl. Or D. Declination. M. Minutes of Time. | N. P. D. Dist. From North Pole. OTHER ABBREVIATIONS USED IN THE ALMANAC. S. , South, _i. E. _, crosses the meridian; M. , morning; A, Afternoon;Gr. H. L. N. , greatest heliocentric latitude north, _i. E. _, greatestdistance north of the ecliptic, as seen from the sun. [Symbols]Inf. , inferior conjunction; Sup. , superior conjunction. GREEK ALPHABET USED INDICATING THE STARS. a, alpha. | ae, eta. | n, nu. | t, tau. B, beta. | th, theta. | x, xi. | u, upsilon. G, gamma. | i, iota. | o, omicron. | ph, phi. D, delta. | k, kappa. | p, pi. | ch, chi. E, epsilon. | l, lambda. | r, rho. | ps, psi. Z, zeta. | m, mu. | s, sigma. | o, omega. [Page 276]CHAUTAUQUA OUTLINE FOR STUDENTS. As an aid to comprehension, every student should draw illustrativefigures of the various circles, planes, and situations described. (For example, see Fig. 45, page 112. ) As an aid to memory, theportion of this outline referring to each chapter should be examinedat the close of the reading, and this mere sketch filled up to aperfect picture from recollection. I. _Creative Processes. _--The dial-plate of the sky. Cause or differentweights--on sun, moon. Two laws of gravity. Inertia. Fall of earthto sun per second. Forward motion. Elastic attraction. Perturbationof moon; of Jupiter and Saturn. Oscillations of planets. II. _Light. _--From condensation. Number of vibrations of red; violet. Thermometer against air. Aerolite against earth. Two bolides againstthe sun. Large eye. Velocity of light. Prism. Color means differentvibrations. Music of light. Light reports substance of stars. Forceof; bridge, rain, dispersion, intensities, reflection, refraction, decomposition. III. _Astronomical Instruments. _--Refracting telescope. Reflecting;largest. Spectroscope. Spectra of sun, hydrogen, sodium, etc. Emade G by approach; C by departure. Stars approach and recede. IV. _Celestial Measurements. _-Place and time by stars. Degrees, minutes, seconds. Mapping stars. Mural circle. Slow watch. HoosacTunnel. Fine measurements. Sidereal time. Spider-lines. Personalequation. Measure distance--height. Ten-inch base line. Parallaxof sun, stars. Longitude at sea. Distance of Polaris, a Centauri, 61 Cygni. Orbits of asteroids. V. _The Sun. _--World on fire. Apparent size from planets. Zodiacallight. Corona. Hydrogen--how high? Size. How many earths? Spots:1. Motion; 2. Edges; 3. Variable; 4. Periodic; 5. Cyclonic; 6. Size; 7. Velocities. What the sun does. Experiments. VI. _The Planets from Space. _--North Pole. Speed. Sizes. Axialrevolution. Man's weight on. Seasons. Parallelism of axis. Earthnear [Page 277] sun in winter. Plane of ecliptic. Orbits inclinedto. Earth rotates. Proof. Sun's path among stars. Position ofplanets. Motion--direct, retrograde. Experiments. VII. _Meteors. _--Size; number; cause of; above earth; velocity;colors; number in space; telescopic view of. Aerolites: Systemsof; how many known. Comets: Orbits; number of comets; Halley's;Biela's lost; Encke's. Resisting medium. Whence come comets? Composedof what? Amount of matter in. [Symbol]. VIII. _The Planets. _--How many? Uranus discovered? Neptune? Asteroids?Vulcan? Distance from sun. Periodic time. Mercury: Elements; shapes, as seen from earth; transits. Venus: Elements; seen by day; hownear earth? how far from? phases; Galileo. Earth: Elements; inspace; Aurora; balance of forces. Tides: Main and subsidiary causes;eastern shores; Mediterranean Sea. Moon: Elements; hoax; moves east;see one side; three causes help to see more than half. Revolution:Why twenty-nine and a half days: heat--cold; how much light? Cratersand peaks lighted; measured. Eclipses--Why not every new and fullmoon? Periodicity. Mars: Elements; how near earth? How far from?Apparent size; ice-fields; which end most? Satellites--Asteroids:How found? When? By whom? How many? Jupiter: Elements; trade-winds;how much light received? Own heat. Satellites: How many? Colors. Saturn: Elements; habitability; rings; flux; satellites. Uranus:Elements; discoverer; seen by; moon's motion. Neptune: Elements;discovered by; how? Review system. IX. _The Nebular Hypothesis. _--State it; facts confirmatory. Objections--1. Heat; 2. Rotation; 3. Retrograde; 4. Martial moons;5. Star of 1876. Evolution: Gaps in; conclusion. X. _The Stellar System. _-Motto. Man among stars; open page; starrypoem; stars located; named. Thuban. Etanin. Constellations: Knowthem; number of stars; double; e Lyræ, Sirius, Procyon, Castor, 61 Cygni, g Virginis. Colored stars; change color. Clusters: Twotheories. Nebulæ: Two visible; composed of; shapes; where? Variablestars. Sun. B Lyræ, Mira, Betelguese, Algol; cause. Temporary;1572. New star of 1866: Two theories. Star of 1876. Movements ofstars; Sirius; sun; 1830 Groombridge. Stars near Pleiades: Orion, Great Dipper, Southern Cross. Centre of gravity. XI. _The Worlds and the Word. _--Rich. Number. Erroneous allusions. Truth before discovery: 1. A beginning; 2. Creation before arrangement;3. Light before sun; 4. Mountains under water; 5. Order ofdevelopment; [Page 278] 6. Sphere of earth; 7. How upheld; 8. Numberof stars; 9. Weight of air; 10. Meteorology; 11. Queries to Job; 12. Sun to end of heaven; 13. View of Mitchell; 14. Herschel. What ismatter? Force? End of earth. Way to knowledge. Work of light. Transfiguration of matter. Uniformitarianism. A whisper of Him. Manfor mastery. Each a type of higher. Survival of fittest. Uranus. Worlds and Word one language. XII. _The Ultimate Force. _--Universe shows power: 1. Rain; Niagara;2. Vegetable growth; 3. Worlds carried; 4. Sun; fill dome with worlds;5. Double suns; 6. Galaxies. Correlation. What ultimate? Mind andwill. What continuous relation? Watch. Theories of gravitation:Newton's, Le Sage's, Bible's. High-class energy deteriorates. Searchfor atoms: 1. Microscope; 2. Gold; 3. Infusoria; 4. Musk. Propertiesof atoms: 1. Impenetrable; 2. Indivisible; 3. Shape; 4. Quality; 5. Crystallization; 6. Not touch each other; 7. Active; 8. Attractive;9. Intelligent. Whose? Relation of matter to God; rock to soil. Push upward. Highest has mastery. Man advances by highest. Matterrecapacitated. Refined habitations. Inhabitants. All force leadsback to mind. Personal and infinite. [Page 279]GLOSSARY OF ASTRONOMICAL TERMS AND INDEX. ABBREVIATIONS used in astronomies, 275. ABERRATION OF LIGHT (_a wandering away_), an apparent displacement of a star, owing to the progressive motion of light combined with that of the earth and its orbit, 199. AEROLITE (_air-stone_), 122. AIR, refraction of the, 40. ALGOL, the variable star, 222. ALMANAC, Nautical, 71; explanation of signs used, 275. ALPHABET, Greek, 275. ALTITUDE, angular elevation of a body above the horizon. ANGLE, difference in directions of two straight lines that meet. ANNULAR (_ring-shaped_) ECLIPSES, 158; nebulæ, 218, 220. APHELION, the point in an orbit farthest from the sun. APOGEE, the point of an orbit which is farthest from the earth. APSIS, plural _apsides_, the line joining the aphelion and perihelion points; or the major axis of elliptical orbits. ARC, a part of a circle. ASCENSION, RIGHT, the angular distance of a heavenly body from the first point of Aries, measured on the equator. ASTEROIDS (_star-like_), 162; orbits of interlaced, 74. ASTRONOMICAL INSTRUMENTS, 43. ASTRONOMY, use of, 57. ATOM, size of, 255; power of, 256. AURORA BOREALIS, 143. AXIS, the line about which a body rotates. AZIMUTH, the angular distance of any point or body in the horizon from the north or south points. BAILEY'S BEADS, dots of light on the edge of the moon seen in a solar eclipse, caused by the moon's inequalities of surface. BASE LINE, 68. BIELA'S COMET, 129. BINARY SYSTEM, a double star, the component parts of which revolve around their centre of gravity. BODE'S LAW of planetary distances is no law at all, but a study of coincidences. BOLIDES, small masses of matter in space. They are usually called meteors when luminous by contact with air, 120. [Page 280]CELESTIAL SPHERE, the apparent dome in which the heavenly bodies seem to be set; appears to revolve, 3. CENTRE OF GRAVITY, the point on which a body, or two or more related bodies, balances. CENTRIFUGAL FORCE (_centre fleeing_). CHROMOLITHIC PLATE of spectra of metals, to face 50. CIRCUMPOLAR STARS, map of north, 201. COLORS OF STARS, 214. COLURES, the four principal meridians of the celestial sphere passing from the pole, one through each equinox, and one through each solstice. COMETS, 126; Halley's, 128; Biela's lost, 129; Encke's, 130; constitution of, 131; will they strike the earth? 133. CONJUNCTION. Two or more bodies are in conjunction when they are in a straight line (disregarding inclination of orbit) with the sun. Planets nearer the sun than the earth are in inferior conjunction when they are between the earth and the sun; superior conjunction when they are beyond the sun. CONSTELLATION, a group of stars supposed to represent some figure: circumpolar, 201; equatorial, for December, 202; for January, 203; April, 204; June, 205; September, 206; November, 207; southern circumpolar, 208. CULMINATION, the passage of a heavenly body across the meridian or south point of a place; it is the highest point reached in its path. CUSP, the extremities of the crescent form of the moon or an interior planet. DECLINATION, the angular distance of a celestial body north or south from the celestial equator. DEGREE, the 1/360 part of a circle. DIRECT MOTION, a motion from west to east among stars. DISK, the visible surface of sun, moon, or planets. DISTANCE OF STARS, 70. DOUBLE STARS, 210. EARTH, revolution of, 109; in space, 142; irregular figure, 145. ECCENTRICITY OF AN ELLIPSE, the distance of either focus from centre divided by half the major axis. ECLIPSE (_a disappearance_), 157. ECLIPTIC, the apparent annual path of the sun among the stars; plane of, 106. EGRESS, the passing of one body off the disk of another. ELEMENTS, the quantities which determine the motion of a planet: data for predicting astronomical phenomena; table of solar, 274. ELEMENTS, chemical, present in the sun, 270. ELONGATION, the angular distance of a planet from the sun. EMERSION, the reappearance of a body after it has been eclipsed or occulted by another. [Page 281]EQUATOR, terrestrial, the great circle half-way between the poles of the earth. When the plane of this is extended to the heavens, the line of contact is called the celestial equator. EQUINOX, either of the points in which the sun, in its apparent annual course among the stars, crosses the equator, making days and nights of equal length. EVOLUTION, materialistic, 182; insufficient, 189. FIZEAU determines the velocity of light, 23. FORCES, delicate balance of, 144. GALILEO, construction of his telescope, 43. GEOCENTRIC, a position of a heavenly body as seen or measured from the earth's centre. GEODESY, the art of measuring the earth without reference to the heavenly bodies. GOD, relation of, to the universe, 258. GRAVITATION, laws of, 6; extends to the stars, 13; theories of, 253. GRAVITY on different bodies, 6, 274. HELICAL, rising or setting of a star, as near to sunrise or sunset as it can be seen. HELIOCENTRIC, as seen from the centre of the sun. HOOSAC TUNNEL, example of accuracy, 62. HORIZONTAL PENDULUM, 272. IMMERSION, the disappearance of one body behind another, or in its shadow. INCLINATION OF AN ORBIT, the angle between its plane and the plane of the ecliptic. INFERIOR CONJUNCTION, when an interior planet is between the earth and the sun. JUPITER, apparent path of, in 1866, 112; elements of, 164; satellites of, 165; positions of satellites, 166; elements of satellites, 166; the Jovian system, 167. KEPLER'S LAWS--1st, that the orbits of planets are ellipses, having the sun or central body in one of the foci; 2d, the radius-vector passes over equal spaces in equal times; 3d, the squares of the periodic times of the planets are in proportion to the cubes of their mean distances from the sun. LATITUDE, the angular distance of a heavenly body from the ecliptic. LIGHT, the child of force, 17; number of vibrations of, 18, 25; velocity of, 22; undulatory and musical, 26; chemical force of, 30; experiments with, 37; approach and departure of a light-giving body measured, 51; aberration of, 199. LIMB, the edge of the disk of the moon, sun, or a planet. LONGITUDE. If a perpendicular be dropped from a body to the ecliptic, its celestial longitude is the distance of the foot of the perpendicular from the vertical equinox, counted toward the east; mode of ascertaining terrestrial, 72. MAGELLANIC CLOUDS, 208. [Page 282]MARS, 159; snow spots of, 160; satellites of, 161. MASS, the quantity of matter a body contains. MEAN DISTANCE OF A PLANET, half the sum of the aphelion and perihelion distances. MEASUREMENTS, celestial, 57. MERCURY, 138. MERIDIAN, terrestrial, of a place, a great circle of the heavens passing through the poles, the zenith, and the north and south points of the horizon; celestial, any great circle passing from one pole to the other. METEORS, 119; swarm of, meeting the earth, 118; explosion of, 120; systems of, 123; relation of, to comets, 124. MICROMETER, any instrument for the accurate measurement of very small distances or angles. MIND, origin of force, 252; continuous relation of, to the universe, 252. MILKY WAY, 210, 215. MIRA, the Wonderful, 221. MOON, the, 151; greatest and least distance from the earth, 10; telescopic appearance of, 155. MURAL CIRCLE, 61. NADIR, the point in the celestial sphere directly beneath our feet, opposite to zenith. NEBULÆ, 217. NEBULAR HYPOTHESIS, not atheistic, 182; stated, 182; confirmatory facts, 183; objections to, 185. NEPTUNE, elements of, 175. NODE, the point in which an orbit intersects the ecliptic, or other plane of reference; ascending, descending, line of, 107. OCCULTATION, the hiding of a star, planet, or satellite by the interposition of a nearer body of greater angular magnitude. OPPOSITION. A superior planet is in opposition when the sun, earth, and the planet are in a line, the earth being in the middle. ORBIT, the path of a planet, comet, or meteor around the sun, or of a satellite around a primary; inclination of, 106; earth's, seen from the stars, 70. OUTLINE FOR STUDENTS, 276. PARALLAX, the difference of direction of a heavenly body as seen from two points, as the centre of the earth and some point of its surface, 69. PARALLELS, imaginary circles on the earth or in the heavens parallel to the equator, having the poles for their centre. PERIGEE, nearest the earth; said of a point in an orbit. PERIHELION, the point of an orbit nearest the sun. PERIODIC TIME, time of a planet's, comet's, or satellite's revolution. PERSONAL EQUATION, 65. PERTURBATION, the effect of the attractions of the planets or other[Page 283] bodies upon each other, disturbing their regular motion; of Saturn and Jupiter, 11; of asteroids, 13; of Uranus and Neptune, 176. PHASES, the portions of the illuminated half of the moon or interior planet, as seen from the earth, called crescent, full, and gibbous. PHOTOSPHERE of the sun, 89. PLANET (_a wanderer_), as seen from space, 99; speed of, 101; size of, 102; movements retrograde and direct, 112. POINTERS, the, 197. POLE, NORTH, movement of, 198. POLES, the extremities of an imaginary line on which a celestial body rotates. QUADRANT, the fourth part of the circumference of a circle, or 90°. QUADRATURE, a position of the moon or other body when 90° from the sun. RADIANT POINT, that point of the heavens from which meteors seem to diverge, 118. RADIUS-VECTOR, an imaginary line joining the sun and a planet or comet in any part of its orbit. RAIN, weight of, 249. REFLECTING TELESCOPE, 44. REFRACTING TELESCOPE, 43. REFRACTION, a bending of light by passing through any medium, as air, water, prism. RETROGRADE MOTION, the apparent movement of a planet from east to west among the stars. REVOLUTION, the movement of bodies about their centre of gravity. ROTATION, the motion of a body around its axis. SATELLITES, smaller bodies revolving around planets and stars. SATURN, elements of, 167; revolution of, 168; rings of, 169; decreasing, 171; nature of, 171; satellites of, 172. SEASONS, of the earth, 102; of other planets, 105. SELENOGRAPHY (_lunography_), a description of the moon's surface. SIGNS OF THE ZODIAC, the twelve equal parts, of 30° each, into which the zodiac is divided. SOLAR SYSTEM, view of, 100, 177. SOLSTICES, those points of the ecliptic which are most distant from the equator. The sun passes one about June 21st, and the other about December 21st, giving the longest days and nights. SPECTROSCOPE, 46. SPECTRUM OF SUN AND METALS, 50. STARS, chemistry of, 28; distance of, 70-73; mode of naming, 196; number of, 210; double and multiple, 210; colored, 214; clusters of, 215; variable, 220; temporary, new, and lost, 223; movements of lateral, 226; in line of sight, 269. STATIONARY POINTS, places in a planet's orbit at which it has no motion among the stars. [Page 284]STELLAR SYSTEM, the, 195. SUMMARY OF RECENT DISCOVERIES, 269. SUN, fall of two meteoric bodies into, 19; light from contraction of, 20; as seen from planets, 79; corona, 81; hydrogen flames of, 84; condition of, 89; spots, 90; experiments, 95; apparent path among the stars, 111; power of, 250. SYMBOLS USED IN ASTRONOMY, 275. TELESCOPE, refracting, 43; reflecting, 44; Cambridge equatorial, 46. TELESCOPIC WORK, clusters, 210; double stars, 212. TEMPORARY STARS, 223. TERMINATOR, the boundary-line between light and darkness on the moon or a planet. TIDES, 146. TRANSIT, the passage of an object across some fixed line, as the meridian, or between the eye of an observer and an apparently larger object, as that of Mercury or Venus over the disk of the sun, and the satellites of Jupiter over its disk; of a star, 65. ULTIMATE FORCE, the, 249. URANUS, elements of, 173; moons of, retrograde, 174; perturbed by Neptune, 176. VARIABLE STARS, 220. VENUS, 139. VERNIER, a scale to measure very minute distances. VERTICAL CIRCLE, one that passes through the zenith and nadir of the celestial sphere. The prime vertical circle passes through the east and west points of the horizon. VULCAN, discovery of, 137. WORLDS, THE, AND THE WORD, teach the same truth, 231-245. YEAR, the, length of, on any planet, is determined by the periodic time. ZENITH, the point in the celestial sphere directly overhead. ZODIAC, a belt 18° wide encircling the heavens, the ecliptic being the middle. In this belt the larger planets always appear. In the older astronomy it was divided into twelve parts of 30° each, called signs of the zodiac. ZODIACAL LIGHT, 80. TO FIND THE STARS IN THE SKY. Detach any of the following maps, appropriate to the time of year, hold it between you and a lantern out-of-doors, and you have anexact miniature of the sky. Or, better, cut squares of suitablesizes from the four sides of a box; put a map over each aperture;provide for ventilation, and turn the box over a lamp or candleout-of-doors. Use an opera glass to find the smaller stars, ifone is accessible. [Illustration: Circumpolar Constellations. Always visible. In thisposition. --January 20th, at 10 o'clock; February 4th, at 9 o'clock;and February 19th, at 8 o'clock. ] [Illustration: Algol is on the Meridian, 51° South of Pole. --At 10o'clock, December 7th; 9 o'clock, December 22d; 8 o'clock, January5th. ] [Illustration: Capella (45° from Pole) and Rigel (100°) are onthe Meridian at 8 o'clock February 7th, 9 o'clock January 22d, andat 10 o'clock January 7th. ] [Illustration: Regulus comes on the Meridian, 79° south from thePole, at 10 o'clock March 23d, 9 o'clock April 8th, and at 8 o'clockApril 23d. ] [Illustration: Arcturus comes to the Meridian, 70° from the Pole, at 10 o'clock May 25th, 9 o'clock June 9th, and at 8 o'clock June25th. ] [Illustration: Altair comes to the Meridian, 82° from the Pole, at 10 o'clock P. M. August 18th, at 9 o'clock September 2d, andat 8 o'clock September 18th. ] [Illustration: Fomalhaut comes to the Meridian, only 17° from thehorizon, at 8 o'clock November 4th. ]