Catalog A. 1908. ASTRONOMICAL INSTRUMENTS... AND ... ACCESSORIES. [Illustration] WM. GAERTNER & CO. 5345-5349 Lake Ave. CHICAGO. Catalog A. 1908. ASTRONOMICAL INSTRUMENTS... AND ... ACCESSORIES. [Illustration] WM. GAERTNER & CO. 5345-5349 Lake Ave. CHICAGO. Notice. This catalogue supersedes former editions. The prices given in this catalogue are net and do not include packing whichwill be charged at cost. To avoid mistakes and delays when ordering please give catalogue number andshipping instructions. Most of the instruments listed in this catalogue are constructed to orderonly but the smaller sizes of telescopes with accessories, chronographs, simpler measuring machines, etc. , are usually kept in stock. The apparatus listed in this catalogue is of our own manufacture, exceptingthe astronomical regulator clocks, which we have listed for the convenienceof our customers. All orders will be filled as promptly as possible with due regard tothorough workmanship and efficient inspection. Everything that leaves our establishment is carefully tested and inspectedand we can guarantee our apparatus to be, in every respect, fully asrepresented. Any piece, which does not come up to the most exactingrequirements will always be promptly replaced within the shortest possibletime. We shall be glad to satisfy any special requirements of our customers andwill make any desired alterations and additions on the standard designs. Introduction. In the following pages we have endeavored to give to our customers an ideaof the line of astronomical instruments of the latest and most improvedtypes which we have constructed for some of the leading observatories asmentioned in the text. We feel that this series of illustrations may notonly be of general interest, but also of service in helping to determinefurther developments of modern astronomical and astrophysical equipment. Wehave not thought it advisable to describe in detail the various instrumentsof precision, which we have been called upon to construct from time to timefor the scientists in the astronomical as well as other branches of scienceduring the last ten years. As a rule every astronomer is interested in somespecial line of research, which for a successful investigation requires aspecial adaptation of the instrument he proposes to use, and in such caseswe are confident we can fill the requirements and shall be happy tocorrespond with interested parties. We are in position to undertake thedesign of special apparatus and can furnish sketches and estimates inaccordance with the suggestions of the customer on short notice in suchcases, where the importance of the prospective business will warrant it. Among the various instruments which we have built, but which are notincluded in this catalogue, we wish to mention, spectroheliographs, planetary cameras, photographic plate holders, domes for observatories, etc. The optical parts which we furnish are of the highest degree of excellenceand are made for us by several of the most reliable firms in this line. Mr. O. L. Petitdidier is closely located to our works, and during the lastten years has supplied most of our objectives, etc. It is and has been the aim of our firm to produce apparatus of the highestgrade and the constant growth of our business is a mute but eloquenttestimonial that our efforts have been appreciated by our customers. We are glad to acknowledge our indebtedness to many of the foremostastronomers, who have greatly assisted us by suggestions as to theirparticular requirements, and by supplying certain of the photographs herereproduced. We take this opportunity to thank our customers for the favors rendered usin the past, and trust that in the future these mutually pleasant relationsmay be renewed. [Illustration: A 101] #A101. Alt-Azimuth Mounting# on strong hardwood tripod. The vertical andhorizontal axis have large bearing surfaces, assuring stability andsteadiness of motion. All parts excepting the tripod head are made of brassand are nicely finished. The telescope is fitted with long rack and pinionmotion. Three celestial eye pieces are included. Price with 2½"telescope #$90. 00# #A102. # The same as above with 3" telescope. Price #$110. 00# #A103. # The same as above with 3½" telescope. Price #$140. 00# #A104. # The same as above with 4" telescope. Price #$200. 00# #Note. #--All our astronomical telescope have objectives of the standardfocal length (focus = to about 15 times diameter of aperture). Theobjective is mounted in the most approved manner and is provided withadjustment for collimation. #Note. #--For accessories to these telescopes see page 11. [Illustration: A 110] #A110. Universal Equatorial Mounting. # This form of mounting can be usedequally well for celestial and terrestrial observations. The mounting ismade to swivel on the tripod head, in order to set the instrument in themeridian. The polar axis can be set at any latitude and a graduated arcgives the exact position. The instrument is set level by means of two smalllevels attached to the tripod top. The polar axis is fitted with worm wheeland worm for slow motion. The handle with the universal joint can beclamped on either side of the worm shaft. Telescope of 3" aperture andthree eye pieces. Price #$165. 00# #A111. # Same as above with 3½" telescope. Price #$190. 00# #A112. # Same as above with 4" telescope. Price #$250. 00# For accessories see page 11. [Illustration: A 120] #A120. Portable Equatorial Mounting with Driving Clock. # This instrumentwas designed to meet the demand for portable low priced telescope suitablefor the study of astronomy in the college, high school or for the amateurastronomer. Every observer and teacher in astronomy will appreciate thegreat usefulness of a driving mechanism, which will keep the star in thefield during observation. After several years of experimenting we havesucceeded in constructing a reliable clock which can easily be attached toour portable telescope mounting. The instrument is mounted on strong hardwood tripod fitted with iron shoes. It is attached to the tripod top by a single screw which holds it firmlyand allows adjustment in azimuth. The clock case carrying the bearing forthe polar axis is made to swivel in the base casting, so that the polaraxis may be easily set and firmly clamped at an angle from horizontal tovertical. A level is fitted to the tripod top and a graduated arc isfastened to the clock case. If the polar axis is set vertical and the wormwheel unclamped, the instrument is transformed into an alt-azimuthmounting. This feature will be found to be a great convenience especiallyfor terrestrial observations. Both the polar and declination axes are carefully fitted to their bearingsand carry finding circles. The right ascension circle reads to 5 min. , thedeclination circle to single degrees. The declination axis is fitted withclamp screw which is within convenient reach. The clock has ample power and is enclosed in a heavy case which protects itfrom dust and injury. It is driven by two strong springs and will run about12 hours without rewinding. A lever for starting or stopping is provided. Motion from clock to polar axis is transmitted by means of a set of bevelgears and worm and worm wheel. The worm wheel is held by friction to thepolar axis so that the telescope can be moved without loosening any screwand without affecting the clock. The clock will give steady and accuratemotion to the telescope and with ordinary care it will keep in good repairfor years. A slow motion adjustment independent of the clock is fitted tothe polar axis. With the instrument are furnished three celestial eye pieces giving amagnifying power of about 50, 100 and 150 diameters respectively. The instrument is easily portable, the total weight of a 3" telescope beingabout 60 lbs. Yet it is made heavy enough, and the material welldistributed to insure strength and steadiness. Workmanship and finish ofthe instrument are the best. The brass parts are either lacquered yellow orbronzed. The iron parts are durably enameled and all exposed steel partsare nickel-plated. #A120. # Telescope of 3" aperture. Price #$190. 00# #A121. # Telescope of 3½" aperture, the same as above but the bearing partsmade proportionally heavier. Price #$240. 00# #A122. # Telescope of 4" aperture. Price #$320. 00# For accessories see page 11. #Note. #--An iron column can be provided for above telescopes in place of ofthe tripod, at an extra cost of $20. 00. [Illustration: A 130] EQUATORIAL MOUNTINGS ON IRON PILLAR WITH DRIVING CLOCK, ETC. On page 10 is shown an illustration of our standard high grade type of 6in. Equatorial. A description of the same will apply to practically alllarger and smaller sizes. The pillar is of rectangular cross section and well proportioned. The clockcase is securely fastened to the top of the pillar but with provision foradjustment in azimuth. The clock has ample driving power, is very carefullyconstructed and regulated by friction governor (Design Prof. Young. )Maintaining gears are provided on the main shaft which allows the windingof the clock without retarding motion. Worm wheel and worm are carefullycut, and protected by brass shields. Right ascension and declinationcircles have fine graduation on solid silver and coarse finding graduationon the edge. Electric illumination and magnifying glasses are fitted to theverniers. The handles for all clamps and slow motions are fastenedconveniently near the eye end of the telescope and are of different shapeso as to distinguish in the dark right ascension and declination. The axesare of tool steel carefully fitted to their bearings, and on the largerinstruments friction rollers are fitted to the polar axis. The telescopetube is made of steel, light but strongly constructed. The eye end has longand heavy rack and pinion motion and the whole can be easily removed. #Note. #--The fine divided circles are often omitted on smaller equatorials, as they are not essential, the electrical illumination for the circles isalso left off, and this will amount to a material saving. #A130. Equatorial Mounting with 5 in. Telescope. # According to abovedescription with first class objective, and five eye pieces. Price #$950. 00# The same instrument without fine circles and electrical illumination. Price #$825. 00# #A131. Equatorial Mounting with 6 in. Telescope. #Complete as A130. Price #$1500. 00# #A132. Equatorial Mounting with 8 in. Telescope. #Same as above. Price #$2500. 00# #A133. Equatorial Mounting with 9 in. Telescope. #Same as above. Price #$3300. 00# #A134. Equatorial Mounting with 10 in. Telescope. #Same as above. Price #$3700. 00# #A135. Equatorial Mounting with 12 in. Telescope. #Same as above. Price #$5500. 00# #Note. #--We are equipped to construct larger instruments and are glad togive prices on application. [Illustration: A 131] [Illustration] The above cut shows a driving clock for our standard 6 in. Telescope. We have constructed clocks for a number of larger telescopes among othersthe clock for the 24 in. Lowell Refractor. ACCESSORIES TO TELESCOPES A101 TO A135. #A140. Finder# fitted to 3" telescope. Price #$12. 00# #A141. Finder# fitted to 3½" telescope. Price #$15. 00# #A150. Positive Eye Pieces. # (Ramsden), focus 6 mm. To 25 mm. Price #$4. 50# #A151. Negative Eye Pieces. # (Huygenian), focus 5 mm. To 25 mm. Price #$4. 50# #A152. Diagonal Eye Piece. # The prism of the eye piece has guaranteedoptically plane surfaces and will not affect the definition of thetelescope. Price #$12. 00# #A153. Terrestrial Eye Piece#, focus 25 mm. Price #$12. 00# #A154. Sun Caps#, to fit above eye pieces. Price #$1. 50# The outside diameter of all our eye pieces is 1¼" excepting those used inour Micrometers. [Illustration: A 201] #A201. Position Micrometers for 6" to 8" Telescopes. # Circle 15 cm. Diameter, divisions on solid silver, verniers reading to 6 min. , slow gearmotion for rotating, electrical illumination, provided with different colorscreens. Screw guaranteed of highest accuracy. Price #$200. 00# #A202. Position Micrometers for 4" to 5" Telescopes. # Similar to above butrotation by hand and construction somewhat simpler. Price #$100. 00# [Illustration: A 203] #A203. Small Position Micrometer for 3" to 4" Telescopes. # Circle readsto single degrees. Electric illumination. Price #$75. 00# [Illustration: A 301] #Transit Instrument#, with reversing arrangement, illumination with oil orelectric lamp, Filar micrometer with two eye pieces. Weight of axisbalanced by springs and rollers. The circle has a diameter of 150 mm. , verniers read to 20 seconds. The instrument is mounted on an iron baseplate, which is fitted with azimuth adjustment (not shown in cut). #A301. Transit# with 2" Telescope. Price #$550. 00# #A302. Transit# with 3" Telescope. Price #$800. 00# [Illustration: A 401] #A401. Universal Instrument. # Telescope with objective prism. Verticalcircle has a diameter of 13 cm. Is divided to 10 min. And reads by means oftwo micrometer microscopes to 10 sec. The telescope is fitted with hardphosphor bronze bearing rings and is reversible. Aperture of objective is30 mm. Two eye pieces are furnished giving magnification of 20 and 30diameters. The prism has absolutely plane surfaces and will not affect thedefinition. Striding level reads to 2 sec. The horizontal circle isprotected and reads by means of two verniers to 1 min. The instrument ispacked in a light but strong case. Price complete with tripod #$420. 00# #Note. #--This instrument was first constructed for Mr. E. De K. Leffingwell, who has found it very satisfactory for his work in the polarregions. [Illustration: A 501] #A501. Zoellner Astrophotometer. # The instrument is made to attach to theeye end of the telescope and may be used with any size of refractor orreflector. An axis parallel to the telescope tube allows the instrument torotate as a whole. A clamp is provided to hold it in position. Theartificial star is formed by a small incandescent lamp which is adjustablein any direction, and in front of which is mounted a small diaphragm. Thecolor changing device, consisting of Nicol prism and quartz plate, isfitted with a divided circle reading to single degrees. The circlerevolving with the Nicol prism for changing the intensity of the star, hasa diameter of 14 cm. And reads by means of two verniers to 6 min. A concavelens is mounted in the path of the artificial star to make the lightdiverging at the proper angle and a plane parallel plate is adjustablyfixed in the center of the box in order to throw the light in the eyepiece. An achromatic objective in front of the eye piece brings the imagesof the real and artificial star to a focus in the same plane. Price #$150. 00# [Illustration: A 601] [Illustration: A 602] #A601. Small Spectroscope. # Suitable for telescope from 3 to 6 in. Aperture. The collimator and observing telescope have an aperture of 25mm. , focus of 200 mm. Both are fitted with rack and pinion. Thespectroscope may be used with a grating or a 60 degree prism, and for thispurpose has openings for the telescopes at the proper angles. A positioncircle of 75 mm. Diameter, reading to degrees, is fitted to the instrument. The slit has micrometer head. Price, without grating, but including 60 degree prism #$75. 00# #Note. #--This spectroscope can also be used on a support for laboratorywork. #Support# for above spectroscope. Price #$4. 50# #A602. Spectroscope# for telescopes from 6 in. To 18 in. Aperture anddetailed description on application. [Illustration: A 701] #A701. Chronograph# for physical and astronomical work. This chronograph isdesigned to meet the demand for a medium sized, well-made and accurateinstrument of this kind and has given very good satisfaction. The cylinderis 15 cm. In diameter 25 cm. Long, driven by strong, carefully made clockwork, fitted with friction governor. Two different speeds for the cylindercan be obtained by means of change gears. The slow speed of the drum is onerevolution per minute, and at this speed the drum will run for a full hour. The fast speed is 30 seconds per revolution. The carriage is driven bymeans of a screw, the nut of which is made to disengage easily. Price of the instrument complete with two pens and glass cover #$225. 00# #A701a. Chronograph#, the same as A701 but with only one pen. The carriageis so constructed that a second pen can easily be added later. Price withglass cover #$195. 00# #Note. #--Every instrument is carefully tested before being sent out and wecan guarantee the speed not to vary over 1-20 second during the full run ofone hour. Large temperature changes will not affect the speed of the clock. A large number of the chronographs are in use and have given excellentsatisfaction. [Illustration: A 702] #A702. Prof. G. W. Hough's Printing Chronograph. # The instrument consistsof two carefully and accurately constructed clock movements, which aredriven by gravity and controlled electrically by the sidereal clock. Themovements revolve three type wheels. One of these turns once per second, its edge is divided in 50 parts and it is driven by a separate movement. The second wheel turns once per minute and the third once per hour and theywill print the seconds and minutes, while the first will give thehundredths of seconds. A strip of paper is carried over these wheels andmoved forward by the same electro-magnet, which operates the printinghammers. The paper is sufficiently long for 1200 observations includingspacing between records. The operation of the printing hammers is such thatthe uniform motion of the type wheel is not disturbed in the act ofprinting. The whole instrument is mounted on a heavy slate plate 45 cm. By60 cm. , and protected by a glass cover. The manipulation of the apparatus is extremely simple and convenient andthe records obtained are perfectly reliable and accurate within about 0. 01of a second. The saving of time and labor by the printing chronograph isvery considerable and the filing of the records very convenient. This printing chronograph has been in use at the Dearborn Observatory forabout twenty years and during the last five years the followingobservatories have been equipped with the instrument: Amherst CollegeObservatory; Case School of Applied Science, Cleveland; PhiladelphiaObservatory; Durham Observatory, Durham, England; Observatory of LaPlatta, Argentine; and Dominion Observatory, Ottawa, Canada. Prof. Hough has kindly consented to inspect every chronograph before itleaves our shop. Price, complete on stand, glass cover, etc. #$500. 00# [Illustration: A 801] [Illustration: A 802] #A801. Laboratory Clock. # This is an eight-day clock; has a movement of thebest workmanship, is driven by two strong springs, and keeps accurate time. The dial is 12 inches in diameter and has hour, minute and second hands. Pendulum beats seconds and makes electric contact by means of an adjustablemercury cup. It is mounted in a hardwood case with glass door. Price #$27. 00# #A802. Laboratory Clock. # The same as preceding one, but with better clockmovement, gravity driven. Price #$35. 00# #A803. Regulator Clock. # This clock has a first-class eight day movementwith cut steel pinions. It is fitted with mercury compensation pendulum andelectrical seconds contact. Price #$200. 00# #Note. #--We can furnish free of duty to educational institutionsastronomical precision clocks made by C. Riefler, Germany, and will bepleased to quote prices to interested parties. [Illustration: A 1200] #A1200. Simple Comparator. # (Fig. A1200. ) Built up of #Micrometer Slide#M301 and #Microscope# M101, #with support# M310 #Fitted with Stage#. Thestage is 150 mm. Long and provided with clips for holding objects, such asspectrum photographs, scales, etc. , and is fitted with illuminating mirror. Price #$45. 00# #A1201. Small Comparator. # The instrument is intended for measuring spectraphotographs, gratings, divided scales, or such objects which can be focusedby the microscope and will allow rapid measurements of the highest possibleaccuracy. The measurement depends on the accuracy of the micrometer screw, which is cut and corrected with great care. The screw has a pitch of . 5 mm. And diameter of 15 mm. The index head attached to the screw is ofconsiderable diameter so as to allow the direct reading of . 001 mm. Thehead is divided on solid silver in 500 parts, and carries two rows offigures indicating the first and second half of the mm. The full mm. Areread by means of a scale in front of the instrument. The bed plate isheavy, of cast iron, and the guides are carefully scraped true within 0. 001mm. The carriage has a movement of 80 mm. , is made of gun metal and fittedexactly to the guides; it is also provided with a second or top carriagewith 40 mm. Motion. The top carriage can be moved by hand and accuratelyset by means of a micrometer screw. The microscope is of variablemagnifying power, focused by rack and pinion. Illumination for transparentobjects is given from below by means of a plane mirror. The instrument ismounted on heavy supports, under an angle to make it convenient for theobserver. The instrument is finished in first-class manner, and the ironbed plate heavily copper and nickel plated. The design of this machine was suggested by Prof. Edwin Frost of the YerkesObservatory, where a number of these machines have been in constant useduring the last five years. Careful tests have shown the screw accuratewithin . 0003 of a mm. Throughout the full length. Price #$175. 00# #Note. #--The micrometer on microscope as shown in cut is not furnished withinstrument. A tangent screw for revolving the eye piece with the spider thread can beattached at a cost of $5. 00. [Illustration: A 1201] [Illustration: A 1202] #A1202. Comparator for Measuring Spectra Photographs, Scales, Etc. # Range50 cm. The microscope travels on carefully straightened ways, and is movedby a screw of 1 mm. Pitch. The screw head is faced with a silver band andis divided in 1000 parts. The handle for turning the screw is placed on theleft side of the instrument so as to have the right hand free for recordingreadings. A set of change gears can easily be engaged to give a fast motion to thecarriage. The stage will hold plates from 3 to 8 cm. In width and of 60 cm. In length. It can be shifted lengthwise for a distance of 25 cm. And isprovided with adjustment for aligning the plates. The whole stage can beeasily removed from the instrument. The microscope is fitted with variable magnifying power and is of standardsize. Price #$450. 00# #Note. #--The design of this comparator was suggested by Prof. Humphries, Director Laboratory of the U. S. Weather Bureau, for whom the first one wasbuilt. [Illustration: A 1203] #A1203. Comparator for Star Photographs#, measures in one direction 80 mm. And under right angle 60 mm. The lower part is constructed similar to ourComparator A1201. The top slide carries a divided circle for measuringposition angles. The circle is arranged similar to a position micrometer. It is fitted with quick gear motion and tangent screw and the two verniersread to 1-100 degree. The microscope has variable magnifying power and isprovided with reversing eye piece. This machine has been furnished for andis in use at Yerkes, Lick and Kirkwood Observatories. Price #$365. 00# [Illustration: A 1204] #A1204. Comparator. # For Plates 8×10 inches. This machine was constructedin accordance with suggestions given by Dr. Frank Schlesinger, Director ofAllegheny Observatory. The ways are carefully straightened to within 0. 002millimeter. The carriage is moved by two racks and pinions and has a largehandle on each side. Two concentric circles are fitted to the carriage, theinner circle carries the plate with the film in a fixed plane, no matterwhat the thickness of the glass may be. Both circles are provided withclamps and tangent screws, so that each one may be clamped and adjustedindependently. The outside circle carries four index points 90 degreesapart. One of these marks is made adjustable. These four marks serve toturn the plate exactly 90 degrees so as to measure rectangularcoordinates. The guide carrying the measuring microscope is adjustedexactly at right angles to the ways of the bed plate. The carriagesupporting the microscope is moved by rack and pinion. The microscope isarranged to tilt, so as to view either the plate or the scale above. Theeye piece is provided with a reversing prism. Measurements are made on thescale divided in millimeters. The smaller measurements, to 1-4000 of a mm. , are made by the micrometer. The micrometer is fitted with sliding eye pieceand counter for full revolutions. The scale is not marked in the usual waywith single lines, but each millimeter is marked with a double line. Thisdouble line allows the use of one single spider thread, which is preferableto use for bisecting the star, and the double line on the scale allows aclear setting with the single spider thread. The stage is fitted with anadaptor for holding plates 4×5 inches. Price #$450. 00# This machine has been in use during the last years at the YerkesObservatory and has been found very convenient and satisfactory in everyway. A graduated circle can be provided if desirable. Such division on solidsilver, with verniers reading to 1-100 of a degree will increase the cost$50. 00. #A1205. Comparator#, for plates 4×5 in. Of the same design as A1204. Price #$300. 00# [Illustration: A 1206] #A1206. Comparator. # A larger machine of the same design as A1204 withscale of 45 cm. Length, divided in double lines to 0. 25 mm. , and with twocarriages, one for spectrum plates of 18 in. Length and the other withdivided circles for star photographs 12"×14". This instrument wasconstructed for the Solar Observatory of the Carnegie Institution at MountWilson, California. [Illustration: COELOSTAT. As built for the United States Naval Observatory after design furnished byMr. W. W. Dinwiddie. ] [Illustration: ARMILLARY SPHERE. Built after design of Prof. J. F. Lanneau, Wake Forest College, N. C. ] _NOVEMBER, 1905_ Wm. Gaertner & Co. Astronomical, physical and physiological Apparatus 5347-5349 LAKE AVENUE CHICAGO [Illustration] Spectrometers and Accessories #Cat. No. L4020 LABORATORY SPECTROMETER. # This instrument is very rigid andaccurate in construction and every part of its design has been carefullyconsidered. The circle has a diameter of 15 cm. And the two verniers readto 20 sec. It is fitted with protecting plate which adds greatly to thevalue of the instrument if put in the hands of students. The graduation ison solid silver. The verniers are fitted with adjustable magnifyingglasses, the telescopes have an aperture of 25 mm. , focal length of 200 mm. A horizontal adjustment for the telescope is provided. No provision ismade for radial adjustment, which correction is made before the instrumentis sent out. The slit is accurately constructed; the jaws are of Germansilver and it is provided with comparison prism. The eye end of theobserving telescope is of standard size so as to receive our micrometersM201 or M202, or the Auto Collimating eye piece (Lamont & Abbe) M540. Gauzeeye piece is fitted to the instrument. The prism table and observingtelescope have independent movements and each is provided with clamp andtangent screw. The prism table can be clamped to any part of the vernierplate. The prism holder has convenient leveling arrangement and will holdprism up to 35 mm. In height. The instrument is arranged to receive Fuesscentering apparatus and crystal holder. A 60 degree heavy flint glass prismof best optical quality is included. Price $75. 00 #L4020b CAMERA ATTACHMENT# will fit in place of the observing telescope. Itis fitted with long focus objective and standard plate holder 2½"×2½". Theplate holder is provided with swivel for proper focusing of the spectrum. The slit is so arranged that four exposures can be made on one plate. Price $20. 00 #Cat. No. L4020c SCALE TUBE. # The third arm of the instrument can be easilyattached and rotated and clamped in any position. It may also be used forholding a second Collimator. Price $20. 00 #Cat. No. L4021 STUDENT'S SPECTROMETER. # This instrument is in everyrespect similar to our L4020, but some of the higher finish has beenomitted. All the essentials are carefully constructed and the optical partsare of the best quality. The circle is protected but only one vernierreading to 30 sec. Is fitted to the instrument. The magnifying glass isomitted. Price, including prism $60. 00 [Illustration] [Illustration] TRANSCRIBERS' NOTES General: Corrections to punctuation have not been individually noted. General: Inconsistent spelling of catalog/catalogue preserved as inoriginal. Page 7: magnifiing corrected to magnifying and celestrial corrected tocelestial. Page 17: intensisy corrected to intensity. Page 18: hundreths corrected to hundredths. LaPlatta as in original. NB The final two pages of the book, on Astronomical, physical andphysiological Apparatus, are in a slightly different format in theoriginal. Particularly, prices are not in bold. That has been preserved inthis version.