,catalog ,a4 #aijh4 ,,astronomical ,,instruments 444 ,,and 444 ,,accessories4 ,illustration ,,wm4 ,,gaertner ,,co4 #ecde-ecdi ,lake ,ave4 ,,chicago4 ,catalog ,a4 #aijh4 ,,astronomical ,,instruments 444 ,,and 444 ,,accessories4 ,illustration ,,wm4 ,,gaertner ,,co4 #ecde-ecdi ,lake ,ave4 ,,chicago4 ,notice4 ,this catalogue supersedes former editions4 ,the prices given in this catalogue are net and do not include packing which will be charged at cost4 ,to avoid mistakes and delays when ordering please give catalogue number and shipping instructions4 ,most of the instruments listed in this catalogue are constructed to order only but the smaller sizes of telescopes with accessories1 chronographs1 simpler measuring machines1 etc41 are usually kept in stock4 ,the apparatus listed in this catalogue is of our own manufacture1 excepting the astronomical regulator clocks1 which we have listed for the convenience of our customers4 ,all orders will be filled as promptly as possible with due regard to thorough workmanship and efficient inspection4 ,everything that leaves our establishment is carefully tested and inspected and we can guarantee our apparatus to be1 in every respect1 fully as represented4 ,any piece1 which does not come up to the most exacting requirements will always be promptly replaced within the shortest possible time4 ,we shall be glad to satisfy any special requirements of our customers and will make any desired alterations and additions on the standard designs4 ,introduction4 ,in the following pages we have endeavored to give to our customers an idea of the line of astronomical instruments of the latest and most improved types which we have constructed for some of the leading observatories as mentioned in the text4 ,we feel that this series of illustrations may not only be of general interest1 but also of service in helping to determine further developments of modern astronomical and astrophysical equipment4 ,we have not thought it advisable to describe in detail the various instruments of precision1 which we have been called upon to construct from time to time for the scientists in the astronomical as well as other branches of science during the last ten years4 ,as a rule every astronomer is interested in some special line of research1 which for a successful investigation requires a special adaptation of the instrument he proposes to use1 and in such cases we are confident we can fill the requirements and shall be happy to correspond with interested parties4 ,we are in position to undertake the design of special apparatus and can furnish sketches and estimates in accordance with the suggestions of the customer on short notice in such cases1 where the importance of the prospective business will warrant it4 ,among the various instruments which we have built1 but which are not included in this catalogue1 we wish to mention1 spectroheliographs1 planetary cameras1 photographic plate holders1 domes for observatories1 etc4 ,the optical parts which we furnish are of the highest degree of excellence and are made for us by several of the most reliable firms in this line4 ,mr4 ,o4 ,l4 ,petitdidier is closely located to our works1 and during the last ten years has supplied most of our objectives1 etc4 ,it is and has been the aim of our firm to produce apparatus of the highest grade and the constant growth of our business is a mute but eloquent testimonial that our efforts have been appreciated by our customers4 ,we are glad to acknowledge our indebtedness to many of the foremost astronomers1 who have greatly assisted us by suggestions as to their particular requirements1 and by supplying certain of the photographs here reproduced4 ,we take this opportunity to thank our customers for the favors rendered us in the past1 and trust that in the future these mutually pleasant relations may be renewed4 ,illustration3 ,a #aja ,a#aja4 ,alt-,azimuth ,mounting on strong hardwood tripod4 ,the vertical and horizontal axis have large bearing surfaces1 assuring stability and steadiness of motion4 ,all parts excepting the tripod head are made of brass and are nicely finished4 ,the telescope is fitted with long rack and pinion motion4 ,three celestial eye pieces are included4 ,price with #b #a_/b telescope #ij4jj ,a#ajb4 ,the same as above with #c telescope4 ,price #aaj4jj ,a#ajc4 ,the same as above with #c #a_/b telescope4 ,price #adj4jj ,a#ajd4 ,the same as above with #d telescope4 ,price #bjj4jj ,note4--,all our astronomical telescope have objectives of the standard focal length 7focus to about #ae times diameter of aperture74 ,the objective is mounted in the most approved manner and is provided with adjustment for collimation4 ,note4--,for accessories to these telescopes see page #aa4 ,illustration3 ,a #aaj ,a#aaj4 ,universal ,equatorial ,mounting4 ,this form of mounting can be used equally well for celestial and terrestrial observations4 ,the mounting is made to swivel on the tripod head1 in order to set the instrument in the meridian4 ,the polar axis can be set at any latitude and a graduated arc gives the exact position4 ,the instrument is set level by means of two small levels attached to the tripod top4 ,the polar axis is fitted with worm wheel and worm for slow motion4 ,the handle with the universal joint can be clamped on either side of the worm shaft4 ,telescope of #c aperture and three eye pieces4 ,price #afe4jj ,a#aaa4 ,same as above with #c #a_/b telescope4 ,price #aij4jj ,a#aab4 ,same as above with #d telescope4 ,price #bej4jj ,for accessories see page #aa4 ,illustration3 ,a #abj ,a#abj4 ,portable ,equatorial ,mounting with ,driving ,clock4 ,this instrument was designed to meet the demand for portable low priced telescope suitable for the study of astronomy in the college1 high school or for the amateur astronomer4 ,every observer and teacher in astronomy will appreciate the great usefulness of a driving mechanism1 which will keep the star in the field during observation4 ,after several years of experimenting we have succeeded in constructing a reliable clock which can easily be attached to our portable telescope mounting4 ,the instrument is mounted on strong hardwood tripod fitted with iron shoes4 ,it is attached to the tripod top by a single screw which holds it firmly and allows adjustment in azimuth4 ,the clock case carrying the bearing for the polar axis is made to swivel in the base casting1 so that the polar axis may be easily set and firmly clamped at an angle from horizontal to vertical4 ,a level is fitted to the tripod top and a graduated arc is fastened to the clock case4 ,if the polar axis is set vertical and the worm wheel unclamped1 the instrument is transformed into an alt-azimuth mounting4 ,this feature will be found to be a great convenience especially for terrestrial observations4 ,both the polar and declination axes are carefully fitted to their bearings and carry finding circles4 ,the right ascension circle reads to #e min41 the declination circle to single degrees4 ,the declination axis is fitted with clamp screw which is within convenient reach4 ,the clock has ample power and is enclosed in a heavy case which protects it from dust and injury4 ,it is driven by two strong springs and will run about #ab hours without rewinding4 ,a lever for starting or stopping is provided4 ,motion from clock to polar axis is transmitted by means of a set of bevel gears and worm and worm wheel4 ,the worm wheel is held by friction to the polar axis so that the telescope can be moved without loosening any screw and without affecting the clock4 ,the clock will give steady and accurate motion to the telescope and with ordinary care it will keep in good repair for years4 ,a slow motion adjustment independent of the clock is fitted to the polar axis4 ,with the instrument are furnished three celestial eye pieces giving a magnifying power of about #ej1 #ajj and #aej diameters respectively4 ,the instrument is easily portable1 the total weight of a #c telescope being about #fj lbs4 yet it is made heavy enough1 and the material well distributed to insure strength and steadiness4 ,workmanship and finish of the instrument are the best4 ,the brass parts are either lacquered yellow or bronzed4 ,the iron parts are durably enameled and all exposed steel parts are nickel-plated4 ,a#abj4 ,telescope of #c aperture4 ,price #aij4jj ,a#aba4 ,telescope of #c #a_/b aperture1 the same as above but the bearing parts made proportionally heavier4 ,price #bdj4jj ,a#abb4 ,telescope of #d aperture4 ,price #cbj4jj ,for accessories see page #aa4 ,note4--,an iron column can be provided for above telescopes in place of of the tripod1 at an extra cost of #bj4jj4 ,illustration3 ,a #acj ,,equatorial ,,mountings ,,on ,,iron ,,pillar ,,with ,,driving ,,clock1 ,,etc4 ,on page #aj is shown an illustration of our standard high grade type of #f in4 equatorial4 ,a description of the same will apply to practically all larger and smaller sizes4 ,the pillar is of rectangular cross section and well proportioned4 ,the clock case is securely fastened to the top of the pillar but with provision for adjustment in azimuth4 ,the clock has ample driving power1 is very carefully constructed and regulated by friction governor 7,design ,prof4 ,young47 ,maintaining gears are provided on the main shaft which allows the winding of the clock without retarding motion4 ,worm wheel and worm are carefully cut1 and protected by brass shields4 ,right ascension and declination circles have fine graduation on solid silver and coarse finding graduation on the edge4 ,electric illumination and magnifying glasses are fitted to the verniers4 ,the handles for all clamps and slow motions are fastened conveniently near the eye end of the telescope and are of different shape so as to distinguish in the dark right ascension and declination4 ,the axes are of tool steel carefully fitted to their bearings1 and on the larger instruments friction rollers are fitted to the polar axis4 ,the telescope tube is made of steel1 light but strongly constructed4 ,the eye end has long and heavy rack and pinion motion and the whole can be easily removed4 ,note4--,the fine divided circles are often omitted on smaller equatorials1 as they are not essential1 the electrical illumination for the circles is also left off1 and this will amount to a material saving4 ,a#acj4 ,equatorial ,mounting with #e in4 ,telescope4 ,according to above description with first class objective1 and five eye pieces4 ,price #iej4jj ,the same instrument without fine circles and electrical illumination4 ,price #hbe4jj ,a#aca4 ,equatorial ,mounting with #f in4 ,telescope4 ,complete as ,a#acj4 ,price #aejj4jj ,a#acb4 ,equatorial ,mounting with #h in4 ,telescope4 ,same as above4 ,price #bejj4jj ,a#acc4 ,equatorial ,mounting with #i in4 ,telescope4 ,same as above4 ,price #ccjj4jj ,a#acd4 ,equatorial ,mounting with #aj in4 ,telescope4 ,same as above4 ,price #cgjj4jj ,a#ace4 ,equatorial ,mounting with #ab in4 ,telescope4 ,same as above4 ,price #eejj4jj ,note4--,we are equipped to construct larger instruments and are glad to give prices on application4 ,illustration3 ,a #aca ,illustration ,the above cut shows a driving clock for our standard #f in4 telescope4 ,we have constructed clocks for a number of larger telescopes among others the clock for the #bd in4 ,lowell ,refractor4 ,,accessories ,,to ,,telescopes ,a#aja ,,to ,a#ace4 ,a#adj4 ,finder fitted to #c telescope4 ,price #ab4jj ,a#ada4 ,finder fitted to #c #a_/b telescope4 ,price #ae4jj ,a#aej4 ,positive ,eye ,pieces4 7,ramsden71 focus #f mm4 to #be mm4 ,price #d4ej ,a#aea4 ,negative ,eye ,pieces4 7,huygenian71 focus #e mm4 to #be mm4 ,price #d4ej ,a#aeb4 ,diagonal ,eye ,piece4 ,the prism of the eye piece has guaranteed optically plane surfaces and will not affect the definition of the telescope4 ,price #ab4jj ,a#aec4 ,terrestrial ,eye ,piece1 focus #be mm4 ,price #ab4jj ,a#aed4 ,sun ,caps1 to fit above eye pieces4 ,price #a4ej ,the outside diameter of all our eye pieces is #a #a_/d excepting those used in our ,micrometers4 ,illustration3 ,a #bja ,a#bja4 ,position ,micrometers for #f to #h ,telescopes4 ,circle #ae cm4 diameter1 divisions on solid silver1 verniers reading to #f min41 slow gear motion for rotating1 electrical illumination1 provided with different color screens4 ,screw guaranteed of highest accuracy4 ,price #bjj4jj ,a#bjb4 ,position ,micrometers for #d to #e ,telescopes4 ,similar to above but rotation by hand and construction somewhat simpler4 ,price #ajj4jj ,illustration3 ,a #bjc ,a#bjc4 ,small ,position ,micrometer for #c to #d ,telescopes4 ,circle reads to single degrees4 ,electric illumination4 ,price #ge4jj ,illustration3 ,a #cja ,transit ,instrument1 with reversing arrangement1 illumination with oil or electric lamp1 ,filar micrometer with two eye pieces4 ,weight of axis balanced by springs and rollers4 ,the circle has a diameter of #aej mm41 verniers read to #bj seconds4 ,the instrument is mounted on an iron base plate1 which is fitted with azimuth adjustment 7not shown in cut74 ,a#cja4 ,transit with #b ,telescope4 ,price #eej4jj ,a#cjb4 ,transit with #c ,telescope4 ,price #hjj4jj ,illustration3 ,a #dja ,a#dja4 ,universal ,instrument4 ,telescope with objective prism4 ,vertical circle has a diameter of #ac cm4 is divided to #aj min4 and reads by means of two micrometer microscopes to #aj sec4 ,the telescope is fitted with hard phosphor bronze bearing rings and is reversible4 ,aperture of objective is #cj mm4 ,two eye pieces are furnished giving magnification of #bj and #cj diameters4 ,the prism has absolutely plane surfaces and will not affect the definition4 ,striding level reads to #b sec4 ,the horizontal circle is protected and reads by means of two verniers to #a min4 ,the instrument is packed in a light but strong case4 ,price complete with tripod #dbj4jj ,note4--,this instrument was first constructed for ,mr4 ,e4 de ,k4 ,leffingwell1 who has found it very satisfactory for his work in the polar regions4 ,illustration3 ,a #eja ,a#eja4 ,zoellner ,astrophotometer4 ,the instrument is made to attach to the eye end of the telescope and may be used with any size of refractor or reflector4 ,an axis parallel to the telescope tube allows the instrument to rotate as a whole4 ,a clamp is provided to hold it in position4 ,the artificial star is formed by a small incandescent lamp which is adjustable in any direction1 and in front of which is mounted a small diaphragm4 ,the color changing device1 consisting of ,nicol prism and quartz plate1 is fitted with a divided circle reading to single degrees4 ,the circle revolving with the ,nicol prism for changing the intensity of the star1 has a diameter of #ad cm4 and reads by means of two verniers to #f min4 ,a concave lens is mounted in the path of the artificial star to make the light diverging at the proper angle and a plane parallel plate is adjustably fixed in the center of the box in order to throw the light in the eye piece4 ,an achromatic objective in front of the eye piece brings the images of the real and artificial star to a focus in the same plane4 ,price #aej4jj ,illustration3 ,a #fja ,illustration3 ,a #fjb ,a#fja4 ,small ,spectroscope4 ,suitable for telescope from #c to #f in4 aperture4 ,the collimator and observing telescope have an aperture of #be mm41 focus of #bjj mm4 ,both are fitted with rack and pinion4 ,the spectroscope may be used with a grating or a #fj degree prism1 and for this purpose has openings for the telescopes at the proper angles4 ,a position circle of #ge mm4 diameter1 reading to degrees1 is fitted to the instrument4 ,the slit has micrometer head4 ,price1 without grating1 but including #fj degree prism #ge4jj ,note4--,this spectroscope can also be used on a support for laboratory work4 ,support for above spectroscope4 ,price #d4ej ,a#fjb4 ,spectroscope for telescopes from #f in4 to #ah in4 aperture and detailed description on application4 ,illustration3 ,a #gja ,a#gja4 ,chronograph for physical and astronomical work4 ,this chronograph is designed to meet the demand for a medium sized1 well-made and accurate instrument of this kind and has given very good satisfaction4 ,the cylinder is #ae cm4 in diameter #be cm4 long1 driven by strong1 carefully made clock work1 fitted with friction governor4 ,two different speeds for the cylinder can be obtained by means of change gears4 ,the slow speed of the drum is one revolution per minute1 and at this speed the drum will run for a full hour4 ,the fast speed is #cj seconds per revolution4 ,the carriage is driven by means of a screw1 the nut of which is made to disengage easily4 ,price of the instrument complete with two pens and glass cover #bbe4jj ,a#gja;a4 ,chronograph1 the same as ,a#gja but with only one pen4 ,the carriage is so constructed that a second pen can easily be added later4 ,price with glass cover #aie4jj ,note4--,every instrument is carefully tested before being sent out and we can guarantee the speed not to vary over #a-bj second during the full run of one hour4 ,large temperature changes will not affect the speed of the clock4 ,a large number of the chronographs are in use and have given excellent satisfaction4 ,illustration3 ,a #gjb ,a#gjb4 ,prof4 ,g4 ,w4 ,hough's ,printing ,chronograph4 ,the instrument consists of two carefully and accurately constructed clock movements1 which are driven by gravity and controlled electrically by the sidereal clock4 ,the movements revolve three type wheels4 ,one of these turns once per second1 its edge is divided in #ej parts and it is driven by a separate movement4 ,the second wheel turns once per minute and the third once per hour and they will print the seconds and minutes1 while the first will give the hundredths of seconds4 ,a strip of paper is carried over these wheels and moved forward by the same electro-magnet1 which operates the printing hammers4 ,the paper is sufficiently long for #abjj observations including spacing between records4 ,the operation of the printing hammers is such that the uniform motion of the type wheel is not disturbed in the act of printing4 ,the whole instrument is mounted on a heavy slate plate #de cm4 by #fj cm41 and protected by a glass cover4 ,the manipulation of the apparatus is extremely simple and convenient and the records obtained are perfectly reliable and accurate within about #j4ja of a second4 ,the saving of time and labor by the printing chronograph is very considerable and the filing of the records very convenient4 ,this printing chronograph has been in use at the ,dearborn ,observatory for about twenty years and during the last five years the following observatories have been equipped with the instrument3 ,amherst ,college ,observatory2 ,case ,school of ,applied ,science1 ,cleveland2 ,philadelphia ,observatory2 ,durham ,observatory1 ,durham1 ,england2 ,observatory of ,la,platta1 ,argentine2 and ,dominion ,observatory1 ,ottawa1 ,canada4 ,prof4 ,hough has kindly consented to inspect every chronograph before it leaves our shop4 ,price1 complete on stand1 glass cover1 etc4 #ejj4jj ,illustration3 ,a #hja ,illustration3 ,a #hjb ,a#hja4 ,laboratory ,clock4 ,this is an eight-day clock2 has a movement of the best workmanship1 is driven by two strong springs1 and keeps accurate time4 ,the dial is #ab inches in diameter and has hour1 minute and second hands4 ,pendulum beats seconds and makes electric contact by means of an adjustable mercury cup4 ,it is mounted in a hardwood case with glass door4 ,price #bg4jj ,a#hjb4 ,laboratory ,clock4 ,the same as preceding one1 but with better clock movement1 gravity driven4 ,price #ce4jj ,a#hjc4 ,regulator ,clock4 ,this clock has a first-class eight day movement with cut steel pinions4 ,it is fitted with mercury compensation pendulum and electrical seconds contact4 ,price #bjj4jj ,note4--,we can furnish free of duty to educational institutions astronomical precision clocks made by ,c4 ,riefler1 ,germany1 and will be pleased to quote prices to interested parties4 ,illustration3 ,a #abjj ,a#abjj4 ,simple ,comparator4 7,fig4 ,a#abjj47 ,built up of ,micrometer ,slide ,m#cja and ,microscope ,m#aja1 with support ,m#caj ,fitted with ,stage4 ,the stage is #aej mm4 long and provided with clips for holding objects1 such as spectrum photographs1 scales1 etc41 and is fitted with illuminating mirror4 ,price #de4jj ,a#abja4 ,small ,comparator4 ,the instrument is intended for measuring spectra photographs1 gratings1 divided scales1 or such objects which can be focused by the microscope and will allow rapid measurements of the highest possible accuracy4 ,the measurement depends on the accuracy of the micrometer screw1 which is cut and corrected with great care4 ,the screw has a pitch of 4#e mm4 and diameter of #ae mm4 ,the index head attached to the screw is of considerable diameter so as to allow the direct reading of 4#jja mm4 ,the head is divided on solid silver in #ejj parts1 and carries two rows of figures indicating the first and second half of the mm4 ,the full mm4 are read by means of a scale in front of the instrument4 ,the bed plate is heavy1 of cast iron1 and the guides are carefully scraped true within #j4jja mm4 ,the carriage has a movement of #hj mm41 is made of gun metal and fitted exactly to the guides2 it is also provided with a second or top carriage with #dj mm4 motion4 ,the top carriage can be moved by hand and accurately set by means of a micrometer screw4 ,the microscope is of variable magnifying power1 focused by rack and pinion4 ,illumination for transparent objects is given from below by means of a plane mirror4 ,the instrument is mounted on heavy supports1 under an angle to make it convenient for the observer4 ,the instrument is finished in first-class manner1 and the iron bed plate heavily copper and nickel plated4 ,the design of this machine was suggested by ,prof4 ,edwin ,frost of the ,yerkes ,observatory1 where a number of these machines have been in constant use during the last five years4 ,careful tests have shown the screw accurate within 4#jjjc of a mm4 throughout the full length4 ,price #age4jj ,note4--,the micrometer on microscope as shown in cut is not furnished with instrument4 ,a tangent screw for revolving the eye piece with the spider thread can be attached at a cost of #e4jj4 ,illustration3 ,a #abja ,illustration3 ,a #abjb ,a#abjb4 ,comparator for ,measuring ,spectra ,photographs1 ,scales1 ,etc4 ,range #ej cm4 ,the microscope travels on carefully straightened ways1 and is moved by a screw of #a mm4 pitch4 ,the screw head is faced with a silver band and is divided in #ajjj parts4 ,the handle for turning the screw is placed on the left side of the instrument so as to have the right hand free for recording readings4 ,a set of change gears can easily be engaged to give a fast motion to the carriage4 ,the stage will hold plates from #c to #h cm4 in width and of #fj cm4 in length4 ,it can be shifted lengthwise for a distance of #be cm4 and is provided with adjustment for aligning the plates4 ,the whole stage can be easily removed from the instrument4 ,the microscope is fitted with variable magnifying power and is of standard size4 ,price #dej4jj ,note4--,the design of this comparator was suggested by ,prof4 ,humphries1 ,director ,laboratory of the ,u4 ,s4 ,weather ,bureau1 for whom the first one was built4 ,illustration3 ,a #abjc ,a#abjc4 ,comparator for ,star ,photographs1 measures in one direction #hj mm4 and under right angle #fj mm4 ,the lower part is constructed similar to our ,comparator ,a#abja4 ,the top slide carries a divided circle for measuring position angles4 ,the circle is arranged similar to a position micrometer4 ,it is fitted with quick gear motion and tangent screw and the two verniers read to #a-ajj degree4 ,the microscope has variable magnifying power and is provided with reversing eye piece4 ,this machine has been furnished for and is in use at ,yerkes1 ,lick and ,kirkwood ,observatories4 ,price #cfe4jj ,illustration3 ,a #abjd ,a#abjd4 ,comparator4 ,for ,plates #hx#aj inches4 ,this machine was constructed in accordance with suggestions given by ,dr4 ,frank ,schlesinger1 ,director of ,allegheny ,observatory4 ,the ways are carefully straightened to within #j4jjb millimeter4 ,the carriage is moved by two racks and pinions and has a large handle on each side4 ,two concentric circles are fitted to the carriage1 the inner circle carries the plate with the film in a fixed plane1 no matter what the thickness of the glass may be4 ,both circles are provided with clamps and tangent screws1 so that each one may be clamped and adjusted independently4 ,the outside circle carries four index points #ij degrees apart4 ,one of these marks is made adjustable4 ,these four marks serve to turn the plate exactly #ij degrees so as to measure rectangular coordinates4 ,the guide carrying the measuring microscope is adjusted exactly at right angles to the ways of the bed plate4 ,the carriage supporting the microscope is moved by rack and pinion4 ,the microscope is arranged to tilt1 so as to view either the plate or the scale above4 ,the eye piece is provided with a reversing prism4 ,measurements are made on the scale divided in millimeters4 ,the smaller measurements1 to #a-djjj of a mm41 are made by the micrometer4 ,the micrometer is fitted with sliding eye piece and counter for full revolutions4 ,the scale is not marked in the usual way with single lines1 but each millimeter is marked with a double line4 ,this double line allows the use of one single spider thread1 which is preferable to use for bisecting the star1 and the double line on the scale allows a clear setting with the single spider thread4 ,the stage is fitted with an adaptor for holding plates #dx#e inches4 ,price #dej4jj ,this machine has been in use during the last years at the ,yerkes ,observatory and has been found very convenient and satisfactory in every way4 ,a graduated circle can be provided if desirable4 ,such division on solid silver1 with verniers reading to #a-ajj of a degree will increase the cost #ej4jj4 ,a#abje4 ,comparator1 for plates #dx#e in4 of the same design as ,a#abjd4 ,price #cjj4jj ,illustration3 ,a #abjf ,a#abjf4 ,comparator4 ,a larger machine of the same design as ,a#abjd with scale of #de cm4 length1 divided in double lines to #j4be mm41 and with two carriages1 one for spectrum plates of #ah in4 length and the other with divided circles for star photographs #abx#ad4 ,this instrument was constructed for the ,solar ,observatory of the ,carnegie ,institution at ,mount ,wilson1 ,california4 ,illustration3 ,,coelostat4 ,as built for the ,united ,states ,naval ,observatory after design furnished by ,mr4 ,w4 ,w4 ,dinwiddie4 ,illustration3 ,,armillary ,,sphere4 ,built after design of ,prof4 ,j4 ,f4 ,lanneau1 ,wake ,forest ,college1 ,n4 ,c4 ,,november1 #aije ,wm4 ,gaertner ,co4 ,astronomical1 physical and physiological ,apparatus #ecdg-ecdi ,,lake ,,avenue ,,chicago ,illustration ,spectrometers and ,accessories ,cat4 ,no4 ,l#djbj ,,laboratory ,,spectrometer4 ,this instrument is very rigid and accurate in construction and every part of its design has been carefully considered4 ,the circle has a diameter of #ae cm4 and the two verniers read to #bj sec4 ,it is fitted with protecting plate which adds greatly to the value of the instrument if put in the hands of students4 ,the graduation is on solid silver4 ,the verniers are fitted with adjustable magnifying glasses1 the telescopes have an aperture of #be mm41 focal length of #bjj mm4 ,a horizontal adjustment for the telescope is provided4 ,no provision is made for radial adjustment1 which correction is made before the instrument is sent out4 ,the slit is accurately constructed2 the jaws are of ,german silver and it is provided with comparison prism4 ,the eye end of the observing telescope is of standard size so as to receive our micrometers ,m#bja or ,m#bjb1 or the ,auto ,collimating eye piece 7,lamont ,abbe7 ,m#edj4 ,gauze eye piece is fitted to the instrument4 ,the prism table and observing telescope have independent movements and each is provided with clamp and tangent screw4 ,the prism table can be clamped to any part of the vernier plate4 ,the prism holder has convenient leveling arrangement and will hold prism up to #ce mm4 in height4 ,the instrument is arranged to receive ,fuess centering apparatus and crystal holder4 ,a #fj degree heavy flint glass prism of best optical quality is included4 ,price #ge4jj ,l#djbj;b ,,camera ,,attachment will fit in place of the observing telescope4 ,it is fitted with long focus objective and standard plate holder #b #a_/bx #b #a_/b4 ,the plate holder is provided with swivel for proper focusing of the spectrum4 ,the slit is so arranged that four exposures can be made on one plate4 ,price #bj4jj ,cat4 ,no4 ,l#djbj;c ,,scale ,,tube4 ,the third arm of the instrument can be easily attached and rotated and clamped in any position4 ,it may also be used for holding a second ,collimator4 ,price #bj4jj ,cat4 ,no4 ,l#djba ,,student',s ,,spectrometer4 ,this instrument is in every respect similar to our ,l#djbj1 but some of the higher finish has been omitted4 ,all the essentials are carefully constructed and the optical parts are of the best quality4 ,the circle is protected but only one vernier reading to #cj sec4 is fitted to the instrument4 ,the magnifying glass is omitted4 ,price1 including prism #fj4jj ,illustration ,illustration ,,transcribers' ,,notes ,general3 ,corrections to punctuation have not been individually noted4 ,general3 ,inconsistent spelling of catalog_/catalogue preserved as in original4 ,page #g3 magnifiing corrected to magnifying and celestrial corrected to celestial4 ,page #ag3 intensisy corrected to intensity4 ,page #ah3 hundreths corrected to hundredths4 ,la,platta as in original4 ,,nb ,the final two pages of the book1 on ,astronomical1 physical and physiological ,apparatus1 are in a slightly different format in the original4 ,particularly1 prices are not in bold4 ,that has been preserved in this version4