LIBRARY 
 
 OF THF. 
 
 UNIVERSITY OF CALIFORNIA. 
 
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 Received (j2^f^ - 
 
 Accession No. d~<3 tf ^ > . Class No. 
 

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The World's Columbian Exposition 
 
 Chicago 1893. 
 
 German Exhibition. Group 21 
 
 Special Catalogue 
 
 of the 
 
 Collective Exhibition of Scientific Instruments and Appliances 
 
 exhibited by the 
 
 Deutsche Gesellschaft fur Mechanik und Optik 
 
 Berlin. 
 
 
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CONTENTS: 
 
 Page 
 
 Introduction 1 
 
 Group 21: 
 
 No. 2751. C. F. Betting, Wehlheiden nr. Kassel 11 
 
 .. 2752. Otto Bohne, Berlin S 11 
 
 .. 2753. Hilmar Bock, Oberweissbach nr. Blankenburg 14 
 
 .. 2750. Doerffel & Faerber, Berlin NW 14 
 
 .. 2754. Arth. Burkhardt, Glashiitte, Saxony 15 
 
 .. 2755. Georg Butenschoen, Bahrenfeld nr. Hamburg 10 
 
 .. 2700. Bernhard Halle, Steglitz nr. Berlin . . . : 17 
 
 .. 2701. A. Hasemann, Berlin C 1.7 
 
 .. 2705. W. A. Hirschmann, Berlin N . 19 
 
 .. 2703. Paul Bunge (Propr. A. T. Herzberg), Hamburg 21 
 
 .. 2700. R, Jung, Heidelberg 24 
 
 .. 2709. Max Kohl, Chemnitz, Saxony 35 
 
 ,. 2770. A. Krtiss (Principal Dr. Hugo Krtiss), Hamburg 42 
 
 ,. 2772. G. Lufft, Stuttgart (Wttrttemberg) 47 
 
 ,. 2773. Jacob Merz, Miinchen 49 
 
 ,. 2774. Oscar Moeller, Hamburg 51 
 
 .. 2770. W. Niehls, Berlin N 53 
 
 .. 2777. Albert Ott, Kempten (Bavaria) 54 
 
 .. 2778. A. Pessler, Freiberg (Saxony) 58 
 
 .. 2779. Reiniger, Gebbeft & Schdll, Erlangen (Bavaria) 58 
 
 .. 2780. Clemens Riefler, Miinchen and Nesselwang ; 01 
 
 .. 2782. F. W. Schieck, Berlin SW. 00 
 
 .. 2783. George Schmidt & v. d. Eltz, Schmiedefeld (Thuringia) . . GO 
 
 .. 2784. Franz Schmidt & Haensch, Berlin S 07 
 
 .. 2787. G. A. Schultze, Berlin S.O ' . 92 
 
 .. 2788. Schulze & Bartels, Rathenow 94 
 
 2780. Schott & Genossen, Jena 90 
 
 2790. Dr. Steeg & Renter, Homburg (Bath Hombtirg) ..... 97 
 
 ,. 2791. C. Staudinger & Co., Giessen 99 
 
Page 
 
 No. 2792. C. A. Steinheil Sohne, Miinchen 108 
 
 .. 2794. Emil Sydow, Berlin NW 120 
 
 2795. Ludwig Tesdorpf, Stuttgart 124 
 
 2796. Wilhelm Uebe, Zerbst-Anhalt 135 
 
 2797. Voigt & Hochgesang, Gottingen 1 37 
 
 2798. Yoigtlaender & Sohn, Braunschweig '. . 141 
 
 2801. Carl Zeiss, Jena 145 
 
 .. 2803. Paul Gebhardt, Berlin S 147 
 
 .. 2804. Grand-Ducal Standardizing Institute for Glass Instruments in 
 
 Ilmenau (Thuringia) 150 
 
 A. The Institute's own manufacture 150 
 
 B. Exhibited by the subjoined firms: 
 
 I. Alexander Ruchler & Sohne, Ilmenau . . . . 151 
 
 II. Alt, Eberhardt & Jaeger, Arlesberg . . '. . . 151 
 
 III. Ephraim G-reiner, Stutzerbacli 152 
 
 IV. Emil Gundelach, Gehlberg 153 
 
 V. Franz Schilling, Gehlberg 155 
 
 VI. H. R. Lindenlaub, Schmiedefeld 15(1 
 
 VII. Strasser & Rhode, Glashutte 150 
 
 2805. W. Dieckmann, Celle (Hannover) 157 
 
 ,. 2808. G. Kromschroder, Osnabrttck 158 
 
 2809. C. Bube, Hannover 15s 
 
 .. 2810. Imperial Physical and Technical Institute. Charlottenburg 
 
 nr. Berlin . . 159 
 
 Beside Group 21: 
 
 No. 1349. Group 123. 119. Hartmann & Braun, Bockenheim-Frankf. o/M. 1(50 
 
 R. Fuess. Steglitz nr. Berlin (German University Exhibition.) 181 
 
INTRODUCTION. 
 
 Deutsche Gesellschaft fur Mechanik und Optik. 
 
 Collective Exhibition of Scientiflc-Instruients and Appliances, 
 
 Group 21. 
 
 Group 21 comprises a collective exhibition of the ,,Deutsche Gesell- 
 schaft fUr Mechanik und Optik'', an association of German mechanicians and 
 opticians formed to encourage and support the manufacture of scientific instru- 
 ments and appliances in every direction. 
 
 The manufacture of scientific instruments and appliances implies a high 
 standard of technical skill and equally advanced scientific knowledge. The 
 progress of this department of applied art and science depends in a greater 
 measure than any other department of industry upon the national standard of 
 political and social requirements ; its development is, therefore, greatly influenced 
 by the political and social condition of a nation. In England the requirements 
 of navigation in the 17th and 18th centuries respecting improved astronomical, 
 nautic and chronometric instruments had reacted beneficially upon the scientific 
 instrument trade and given life to a number of prominent makers whose suc- 
 cessors profited by the traditional fame of their predecessors down to the 
 present day. The case was quite similar in France. Here the introduction of 
 the metric system, the construction of good astronomical and surveying instru- 
 ments and the manufacture of exact weights and measures resulted in a general 
 development of the scientific instrument trade. In Germany the manufacture 
 of scientific instruments has an old place in technical history, as such well- 
 known old names- as Brander of Nuremberg or Ludolph of Leipzic testify. 
 
 Mechanical art attained in Germany real importance only in the begin- 
 ning of this century when the inventions of Keichenbach, the optical discoveries 
 of Fraunhofer, the high skill and achievements of Kepsold, Pistor, Breit- 
 haupt and others obtained for it the universal appreciation of the scientific 
 world. During the years 1860 to 1865 the German instrument trade seemingly 
 degenerated. There was, it must be admitted, a race of able and clever mecha- 
 nicians and opticians who were producing excellent work, but they had not the 
 
 1 
 
2 Introduction. 
 
 power of hindering German scientists of 30 years ago from obtaining their 
 nstruments from French or Englisch rather than German makers. 
 
 The causes of this retrogression in so important a department of industry 
 were partly to be/ound in the unhappy political and commercial condition of 
 Germany, but still more so in the deficient correlation between theory and 
 practice. By a happy coincidence men began to recognize the fact that the 
 prosperity of the scientific instrument trade depended mainly upon the coope- 
 ration of scientific and practical men, just at a time when Germany began 
 to rise politically and commercially. German mechanical and optical industry 
 owes, indeed, its present prominent position, which it has attained within the 
 last 20 years, to the judicious manner in which both these coincident factors 
 were made use of. 
 
 The entire development of German mechanical art during this time has 
 emanated from the full appreciation of the principle that the practical maker 
 must know the intentions of .scientific men which are to be realized by the instru- 
 ments and also the limits of the required exactness, and, vice versa, that the 
 investigator must not be an entire stranger to the manufacture of his instruments, 
 but must know their theory and with critical knowledge only demand that 
 degree of exactness which is necessary for his work or which is attainable. 
 This amalgamation of theory and practice forms the basis of the activity of the 
 Deutsche Gesellschaft fiir Mechanik und Optik", which has now existed 
 for 15 years and whose members, composed of practical and theoretical men 
 from all parts of the empire, combine their efforts and give graphic expression 
 to the results thus obtained in the official organ of the Association, the ,,Zeit- 
 schrift fiir Instrument enkunde" (Journal of philosophical instruments), a jour- 
 nal which comprises the entire subject of scientific technique. The object of 
 the association being to maintain the scientific interest of its members, to solve 
 important technical problems, such as the adoptation of uniform screws and 
 tube-threads in the construction of instruments, and also to watch over the 
 social and political interests of the industry which it represents, it, naturally, 
 had to look upon the technical education of the rising generation of mechani- 
 cians and opticians as one of its prominent duties. Much, indeed, has been 
 done in this direction in Germany within the last 20 years. At the instigation 
 of the Association the Berlin School for Artisans (Handwerkerschule) formed the 
 first evening class for mechanicians, in which apprentices received tuition in 
 drawing, natural philosophy and other subjects which are of practical utility 
 to instrument-makers. This example was followed by numerous other towns 
 and, at the present time, every young mechanician has in most of the larger 
 towns an opportunity to acquire theoretical knowledge in his trade, in many 
 cases under the tutorship of prominent mechanicians ; a few of the larger works 
 have even gone so far as to appoint and maintain at their own expense special 
 teachers for their apprentices. 
 
 Means were also provided for more advanced studies. In Berlin a class 
 was founded for journeymen mechanists and more recently also for electrical 
 engineers in which journeymen in a course of six months had the opportu- 
 nity of advancing their theoretical knowledge so far as to become competent 
 of holding the posts of fore-men, adjusters and other preferred appointments. 
 
Introduction. 3 
 
 A similar school for electrical engineers has been founded some years ago in 
 Francfort-on-the-Main. Naturally, in all these cases the theoretical education 
 is adapted to the practical requirements of the learners. 
 
 Apart of this form of self-help German mechanical industry received a 
 great impetus through the encouragement of art and science afforded hy the 
 government during the last 25 years. The erection of numerous large chemical 
 .and physical laboratories, the exigencies of ordnance survey and geodesy with 
 respect to astronomical and surveying instruments, the influence of the adopt- 
 ion ^of the metric system upon the .manufacture of exact rules, weights and 
 sensitive balances and hydrometers, the reaction of the requirements of mete- 
 orology upon thermometry and barometry, the beneficial influence which the 
 development of the German navy exercised upon the nautical instrument trade 
 and many other influences have created important problems and thus given the 
 impulse to the development of the scientific instrument trade in Germany." 
 Their strongest support, however, the mechanical arts received when the fact 
 became recogniced that to permanently maintain the standard of their deve- 
 lopment it was necessary that there should exist a governmental institution 
 upon which devolved all those investigations and technical processes which 
 exceed the limits of individual means. This led to the foundation of the 
 ^Physikalisch-Technische Keichsanstalt in Berlin-Charlottenburg" (the Im- 
 perial Physical and Technical Institute in Charlottenburg nr. Berlin). The work 
 of the first or physical department of this institution consists in theoretical 
 investigations and the most intricate physical measurements, whilst the second 
 or technical department deals with all questions affecting the practical deve- 
 lopment of technical industry, such as the examination of substances respecting 
 their chemical and physical properties, the examination of new constructions, 
 the testing of optical or thermal glasses and determination of their constants, 
 photometric tests, the production and examination of standard screws for fixing 
 and adjusting (micrometer), very finely divided rules and circles, the examina- 
 tion and attestation of measuring appliances and so forth. It is evident that 
 such direct influence upon manufacture, relieving as it does, the individual, 
 must be of the greatest importance to industry. Indeed, during the 5 years 
 of its existence the Imperial Physical and Technical Institute has done very 
 great service to the mechanical arts, so much so that abroad it has become an 
 object of imitation, and in England and the United States the question of the 
 advisability of founding similar institutions is already being dealt with. 
 
 The outcome of these general and energetic efforts which were mainly 
 stimulated by the zeal and activity of the Director of Institute Dr. L. Loewen- 
 herz, who died but a few months hence in the prime of his life is the high 
 standard which the German manufacture of philosophical instruments has reached. 
 It can self-assuredly enter into competition with the industry of any other country, 
 in many respects it probably even occupies the foremost position. In its cha- 
 racter we distinctly recognize the product of the combined efforts of theory 
 and practice. This character becomes also externally apparent in the geogra- 
 phical distribution of the manufacturing centers of optical and mechanical in- 
 dustry. Owing to its great number of polytechnical colleges and scientific 
 institutions and also to its prominent political and commercial position the 
 capital of the empire has naturally become the center of mechanical industry. 
 
 1* 
 
4 Introduction. 
 
 Next to it come the university towns and the seats of polytechnical colleges, 
 in which, beside the instrument makers holding official appointments in univer- 
 sities and institutions, a number of other instrument-makers are established.. 
 This local association of practical manufacture and scientific research and the 
 daily intercourse of makers and scientists greatly favours, by mutual reaction,, 
 the growth of this branch of applied science. Beside in Berlin, important 
 centers of mechanical art are to be found in Munic, where the great achieve- 
 ments of Fraunhofer and Reichenbach are continued by their successors, and 
 in Hamburg, which, beside excelling in astronomical and surveying instruments- 
 and appliances for spectrum analysis, possesses, as a natural consequence of its 
 importance as a sea-port, prominent works for the manufacture of chronometric 
 and nautical instruments. In several manufacturing towns the construction of 
 electrical measuring instruments and electro-therapeutical appliances forms a 
 prominent feature, e. g. in Berlin, Frankfort-on-the-Main, Stuttgart and Er- 
 langen. Important branches of instrument manufacture are also found in many 
 other towns, where production is favoured by special local conditions. 
 
 It would be impossible to here define the entire extent of the German 
 scientific instrument trade; we must, therefore, limit ourselves to a short 
 sketch of its compass. 
 
 The general stamp of German astronomical instruments corresponds 
 to the intrinsic character of the German methods of astronomical research. 
 The intruments are not so much distinguished -for their size, to which much 
 importance is attached in America, as for their rigidity and greatest possible 
 exactness and highest finish of the constructive details; more importance than 
 to size is attached to ingenious arrangements calculated to minimise the effect 
 of instrumental errors. Important improvements have been made in this 
 direction in the construction of meridian circles of portable transit instruments- 
 and of zenith telescopes. Delicately accurate astronomical levels, whose exces- 
 sively laborious production implies the exercise 6f the greatest patience and care r 
 have at present reached the highest standard of perfection in Germany. -- The 
 reputation of German surveying instruments has gained still further ground 
 during the latter years. Recent ordnance survey and measurements of the earth 
 shape have led to many improvements in theodolites, levelling instruments and 
 tacheometers, and the wants of explorers have suggested particularly compact 
 constructions of these instruments. In the case of the instruments intended for 
 ordinary surveying special attention is paid to arrangements for conveniently 
 centering the instruments and to the stability and handiness of the stands. Also 
 instruments for geophysical research have in recent years undergone important 
 improvements; amongst others, registering mareographs are now made of a 
 degree of perfection which was hitherto unknown. In consequence, almost 
 exclusively German instruments are used in the ordnance surveying work of 
 many countries in all parts of the globe. The manufacture of nautical instru- 
 ments, sextants, octants, mariner's compasses and so forth, has, thanks to the 
 united efforts" of the Imperial Admiralty and the mechanical trade, made such 
 progress that now many instruments which formerly had to be obtained from 
 abroad are not only made in Germany in good quality but even of a superior 
 kind to those made abroad. Particularly noticeable progress originating in the 
 work of the Imperial Assize Commission, has been made in metrological 
 
Introduction. 5 
 
 appliances.' Accurately divided measures for most exact metronomical work 
 are supplied by German instrument makers to all parts of the world. Ger- 
 man balances for chemical, physical and metrological work occupy a fore- 
 most position; it need only be mentioned here that German manufacture of ba- 
 lances had a prominent share in the equipment of the ,,Bureau international 
 des poids et mesures"; great care is bestowed upon accurate sets of 
 weights, and porosity is carefully treated as a source of errors. Also the 
 manufacture of hydrometric instruments has made great strides In Germany; 
 the appliances for the examination of spirits recently constructed under the 
 cooperation of the Imperial Assize Commission realize the most critical exigen- 
 cies of modern applied science. In the department of meteorological instru- 
 ments Germany now occupies the first position. German makers are supplying 
 the leading meteorological stations at home and abroad with the finest register- 
 ing thermometers, barometers, rain gauges and hygrometers; in the first rank 
 among these are the ingenious instruments invented by Prof. Sprung, constructed 
 on the principle of the running-weight balance. Germany produces also a large number 
 of graduated meteorological instruments. Exact standard, travelling and marine 
 barometers, travelling and surveying aneroids are exported in large numbers. 
 Germany excels particularly in the manufacture of thermometers. Laborious 
 and costly experiments made during many years by the Imperial Assize Com- 
 mission , the Imperial Physical and Technical Institute and a number of 
 eminent scientists aided by prominent mechanicians have not only resulted 
 in the discovery of the best methods of constructing thermometers, e. g. of 
 fixing the scale, but above all in the production of a glass, the wellknown 
 Jena standard glass, which is so composed as to eliminate the most serious- 
 defect of the older thermometers, viz. the variability of the zero-point. These 
 achievements which have eventually become of critical importance for the ma- 
 nufacture of clinical thermometers, have brought the thermometer-trade of Ger- 
 many to a very high level. At present the Imperial Physical and Technical 
 Institute tests 10000 thermometers per annum; in the Standardizing and Test- 
 ing Institute at Ilmenau, which is under the controllership of the former, 
 30000 thermometers are tested annually, the greater part of which are for 
 export abroad. 
 
 The optical industry of Germany rules a large portion of the market. 
 This favoured position it owes partly to the continued assiduous efforts of many 
 practical opticians, in particular, however, to the work of Prof. Abbe of Jena, 
 who created the optical basis upon which rests the theory of the microscope 
 and who succeeded, in conjunction with Dr. Schott of Jena, in producing glasses 
 of better optical properties than those which had been previously available. 
 This advance in the production of optical glasses has resulted not only in the 
 improvement of the microscope but also in that of telescopes and photographic 
 lenses. Until 1886, the glass-smelting house founded by Fraunhofer having in 
 the mean time ceased, the entire optical industry of Germany was, with respect 
 to its raw-material, dependent opon the two resources at Paris and Birmingham; 
 but at the same time, it was limited to the few types of crowns and flints which 
 the glass-works at Paris and Birmingham were capable of supplying. The 
 establishment of the Jena glass-works in 1886 placed the opticians of Germany 
 upon their own feet as regards their raw-material for all their productions from 
 
6 Introduction. 
 
 microscope lenses to telescopic objectives. The scientific investigations on the 1 
 correlation of the optical properties of glass and its chemical constitution, which 
 formed the starting point of the smelting of glass in Jena, have at the same 
 time resulted in a considerable extension of the number of glasses which may 
 be applied for purposes of practical optics, and opticians have now a series of 
 new types at their command which vary considerably from the older crowns and 
 flints with respect to refractive and dispersive power. This extension of the 
 range of available material led in several provinces of practical optics to valuable 
 improvements, which naturally originated in Germany. Telescopical optics is 
 that department which hitherto has derived the least benefit from the new 
 glasses. Partly on account of the difficulties attending, with some of the new 
 glasses, the production of large discs sufficiently free from defects and partly 
 because of the aptitude of these fusions to yield to atmospheric influences it 
 has been deemed wiser to continue to employ the older types of crown and 
 flint glass for the manufacture of telescopic objectives. - - In the construction 
 of photographic lenses and of the microscope the greatly extended range in. 
 the refractive and dispersive powers of the glasses has, in the mean time, given 
 rise to many practical successes in valuable conbinations, which with the older 
 material could not possibly be produced. In the case of photographic lenses- 
 this success is mainly due to to the fact that with the new glasses achromatic 
 doublets may be constructed in which at will the positive or the negative member 
 may be made to have the higher refractive index, whilst with the older material 
 achromatization of a collective lens always assigned tt& higher refractive index 
 to the negative, in the case of a dispersive lens to the positive member. The 
 removal of this limitation, which was mainly effected by the introduction of the 
 Jena baryta-glasses, has resulted in a series of new photopraphic combinations. 
 In the case of the microscope the conditions for the utilization of the progress 
 made in glass-smelting were much more favourable; for in this case also such 
 fusions could be employed which are obtainable only in relatively small quantities r 
 and furthermore the material is in a much less degree required to resist external 
 influences. Consequently, even such glasses as the phosphate and baryta-glasses- 
 have been largely employed in microscopic lenses though, for those two con- 
 siderations, entirely out of place in other combinations. These new glass-types 
 have furnished the means for vast improvements in the chromatic and spherical 
 correction of microscope lenses and in the increase of the magnifying power of 
 the ocular (Apochromatic objectives and compensating oculars). Very important 
 is also the German manufacture of spectacles, opera-glasses, stereoscopes 
 and similar instruments. The extensiveness of this branch of industry is 
 perspicuously illustrated by the fact that in one single town, Rathenow, there 
 are 94 independent optical manufacturing concerns employing 1035 persons. - 
 It is not surprising that Germany, being the home of spectrum-analysis, holds 
 a prominent position in the manufacture of spectroscopic apparatus. A number 
 of large optical and mechanical firms are engaged in the manufacture of spec- 
 troscopes and many of these are exported 'to all parts of the world. They range 
 from the largest and finest instruments for astronomical and physical research 
 for chemical and photographic investigations down to the smallest hand spec- 
 troscopes. German Polarization appliances also are famous. We may here 
 mention, beside the apparatus used in chemical and physical examination, in 
 
Introduction. 7 
 
 particular the instruments constructed for the examination of sugar and wine, 
 which are as simple in construction as they are perfect in workmanship. The 
 competention between gas and electric light has, as in other countries so also 
 in Germany, occasioned important improvements in the province of photometric 
 apparatus. In this direction the influence of the Physical and Technical Institute 
 has been most marked, two of its members, Mssrs. Lummer and Brodhun, 
 having devised an ingenious combination of prisms which eliminate an 1 innate 
 defect of Bunsen's photometer and formed the basis of technically valuable 
 appliances. 
 
 The local distribution of optical manufacture in Germany is as follows: 
 
 1) Astronomical telescopes: Munic, Berlin; 
 
 2) Photographic objectives,: Munic, Jena, Brunswick, Berlin, Rathenow ; 
 
 3) Microscopes: Jena, Berlin, Wetzlar, Potsdam, Gottingen; 
 
 4) Binoculars and other terrestrial telescopes: Munic, Brunswick, 
 Berlin, Rathenow; 
 
 5) Spectroscopic Apparatus, Polarimeters , Photometers: Berlin, 
 .Munic, Hamburg, Jena; 
 
 6) Mineralogical preparations (Quartz andcalcite): Homburg, Berlin. 
 Not less important are the Measuring instruments for special purposes 
 
 in physical science made by German makers with that degree of precision 
 which modern physical research demands. We cannot here enter into detailed 
 enumeration of the numerous instruments of this class but will only remind our 
 readers of the crystallographic instruments for determining the geometrical and 
 physical constants of crystals. -- The manufacture of Chemical apparatus is 
 greatly supported by the highly developed glass-industry of Germany, which is 
 centralized in the Thuringian districts. 
 
 The glass industry of Thuringia embraces the manufacture of glass-house 
 and blow-pipe goods. Both these divisions envolve a series of incidental operations, 
 such as glass-grinding, polishing, etching, sandblasting, graduating, standardizing 
 and so forth. 
 
 The glass-house goods comprise mainly: 
 
 1) Glass-tubing for glass -instruments (thermometers, hydrometers, 
 barometers etc.). Glass-houses for these goods are in Gehlberg, 
 Stuetzerbach, Geyersthal, Frauenwald and Jena. The Jena glass- 
 house supplies the Jena standard thermometer glass, which is so 
 distinguished for its minimal thermal defects; it also makes glasses 
 for high temperature thermometers and compound glass tubes; 
 
 2) Glass tubing for the manufacture of artificial fruits, flowers, pearls, 
 toys etc. Glass-houses for these goods are e. g. in Schmalenbuche 
 and in Ernsthausen; 
 
 3) Hollow-glassware and glass-apparatus for chemical, physical, pharma- 
 ceutical, surgical and clinical, commercial and other purposes. This 
 division includes in particular: Boiling flasks, beakers, funnels, cy- 
 linders, air-pumps, incandescent lamps etc. The center 'of manu- 
 facture of these goods is Stuetzerbach ; but they are also made in many 
 other places, e. g. Gehlberg, Ilmenau, Graefenroda and Geyersthal. 
 
8 Introduction. 
 
 The list of blow-pipe goods comprises: 
 
 1) Fine Glass Instruments, which are chiefly made in Ilmenau, Mane- 
 bach, Roda, Elgersburg, Arlesberg and Schmiedefeld ; 
 
 2) Glass Instruments for domestic use; chiefly house, window and 
 bath thermometers. Manufacturing centers: Oberweissbach. Neu- 
 haus, Mellenbach and Langewiesen; 
 
 3) Fruits, flowers, pearls, Christmas tree ornaments, toys and puzzles, 
 marbles etc. Manufacturing centers: Lauscha, Igelshieb, Neuhaus 
 and Ernstthal. 
 
 The social importance of the Thuringian glass-trade is mainly due to the 
 fact that in some places (Stuetzerbach, Gehlberg, Schmiedefeld, Lauscha, Neu- 
 haus) nearly the whole population takes part in the manufacture, while in other 
 localities, such as Ilmenau, Manebach, Elgersburg, Oberweissbach etc., a very 
 large part of the population derives its subsistence from this industry. With 
 the glass-industry is also intimately associated the manufacture of the frame- 
 work for glass-instruments. Thuringia supplies nearly the whole globe with its 
 glass-ware, whilst the philosophical glass -instruments are chiefly made in the 
 larger towns, e. g. Berlin, Bonn, Munic, Cologne etc. The extent and com- 
 mercial value of the Thuringian glass-trade may be gathered from the fact that 
 Thuringia produces annually about 1 million glass -instruments and at least 
 3 millions of glass -appliances. One single firm of glass -instrument makers, - 
 one of the largest concerns, however, it should be added, has an annual turn- 
 over of nearly 1 / 4 million Marks. 
 
 The manufacture of electrical measuring instruments is proportional to 
 the enormous development of electric engineering. Partly owing to the direct 
 participation of scientists in practical work, the manufacture of galvanometers 
 of all kinds, electrodynamometers , ammeters, voltmeters, electricity -counters, 
 resistance-coils and electrical apparatus of all kinds has made great strides. 
 A great number of notable firms devote themselves to this branch of industry 
 and export considerable quantities to foreign countries. 
 
 A large number of the hands employed in electrical engineering pursuits are 
 composed of skilled mechanicians, although owing to the whole sale system of 
 manufacture chiefly unskilled labour finds employment. An idea of the extent 
 of the German trade in electrical measuring instruments may be formed from 
 the following data: About 13000 amperemeters and voltmeters are made annually. 
 Most of these are sent abroad. Scientific instruments for electrical engineering 
 are made by 5 principal firms, which are distributed in Berlin, Munic and 
 Francfort o/M. There is, besides, a large number of smaller firms who, together 
 with instruments belonging to other departments of physical science, make 
 electrical measuring instruments. 
 
 No less importance must be claimed for the German manufacture of 
 electro -therapeutical apparatus. The growth of the manufacture of these 
 appliances during the last 5 or 10 years results probably from the continuously 
 increasing application of electricity : 1) as a curative agent for clinical purposes ; 
 2) as the best illuminant for local examination, in particular of bodily cavities, 
 by the employment of small incandescent lamps, and 3) in operative surgery for 
 
Introduction. 9 
 
 cauterizing. These three forms of application of the electric current were, 
 irrespective of constant improvements made in their own department, greatly 
 encouraged by the general progress of electrical engineering, in particular, 
 however, by the recent utilization of accumulators for therapeutical purposes; 
 quite recently it has even become possible to charge these comparatively small 
 accumulators by means of a thermo-pile, which greatly reduces the inconvenience 
 attending the use of other sources of electricity. Electro-therapeutical appliances 
 are chiefly made in Berlin, Francfort o/M. und Erlangen. 
 
 Physiological instruments also occupy a wide space. We may specially 
 allude to the ophthalmological instruments, in particular, to Helmholtz's. ophthal- 
 moscope, which since its invention has undergone many modifications. 
 
 The manufacture of didactic apparatus has reached a considerable 
 extension, owing to the stress which is laid by modern educational training 
 upon ocular demonstration; not only science colleges and advanced public 
 schools are, accordingly, provided with well equipped laboratories, but also in 
 elementary schools the possession of an adequate amount of apparatus for pur- 
 poses of demonstration is deemed imperative. The German educational appara- 
 tus, which are extensively used in all parts of the globe, satisfy three impor- 
 tant conditions: they are very cheap; they are so dimensioned that all their 
 parts may be easily demonstrated; they are made in their simplest possible 
 form all those details which are necessary only for exact measurements being 
 omitted. 
 
 The extensiveness of the German watch and clock manufacture is a 
 well-known fact. The manufacture of the so-called ,,Schwarzwald" clock gives, 
 in Wuerttemberg and Baden alone, employment to 101 firms. The manufacture 
 of regulators, watches, tower-clocks and watches and clocks for special pur- 
 poses gives work to 51 of the larger establishments; the finest astronomical 
 chronometers and thermometers are naturally only made by a few clock- 
 makers; the reputation of these, however, is far spread. 
 
 We will supplement this condensed sketch of the extent of the German 
 instrument manufacture by a few remarks on the technical means employed. 
 German makers utilize largely, by critical selection, numerous new, principally 
 American, inventions in tool-making, but, generally speaking, they prefer to 
 make their own tools according to their special requirements. German makers 
 require, therefore, perhaps rather more time for their productions than their 
 foreign competitors; the process of manufacture bears also little resemblance 
 to whole-sale manufacture and the system of division of labour is only imper- 
 fectly adopted; possibly we may find in these very facts the explanation of the 
 individuality of the German instruments. 
 
 The commercial value of the German scientific and optical instrument 
 trade is in correspondence with its scientific reputation. This fact will be 
 readily gathered from the following table showing the German export to 
 America, Australia, China and Japan during the last three years: 
 
10 
 
 Introduction. 
 
 Export to 
 
 18891891 
 
 Quantities 
 Hundred Kilos 
 
 Net* 
 
 Value 
 1000 Marks 
 
 Nett 
 
 United States of America 
 British North America 
 
 1849 
 99 
 100 
 25 
 38 
 25 
 21 
 309 
 80 
 39 
 25 
 325 
 411 
 49 
 276 
 207 
 
 3698 
 198 
 320 
 50 
 76 
 50 
 42 
 618 
 160 
 78 
 50 
 650 
 822 
 98 
 552 
 414 
 
 Mexico - 
 
 Central America 
 
 West Indies 
 
 Columbia 
 Venezuela 
 
 Brazil . 
 
 Uruguay 
 
 Ecuador 
 
 Peru . . 
 
 Chile . . 
 
 Argentine Republic 
 
 China 
 
 Japan . 
 
 Australia 
 
 
 The number of persons employed in the manufacture of scientific instruments 
 s considerable, as the following table schows: 
 
 Description of goods. 
 
 Number of 
 establishments. 
 
 Number of 
 
 persons 
 employed. 
 
 Mathematical, physical and chemical in- 
 struments 190 3136 
 
 Optical instruments 150 2408 
 
 Drawing instruments 52 613 
 
 Fine balances 47 443 
 
 Thermometers and barometers . . . '. . 87 1014 
 
 Here only those establishments are considered which employ more than 
 10 persons. The number of those employing less than 10 persons may be 
 roughly estimated at three times the above numbers. 
 
 The collective exhibition, Group 21, forms an elegant picture of the 
 German scientific instrument industry, it does not, however, represent its entire 
 extension. Visitors requiring information on instruments and their makers 
 not found represented in the Exhibition are requested to address the Committee 
 of the ^Deutsche Gesellschaft fiir Mechanik und Optik" in Berlin or 
 the Editor of the w Zeitschrift fiir Instrumentenkunde" in Berlin W. 
 
 Dr. A. Westphal. 
 
C. F. Betting, Kassel. Otto Bohne, Berlin. ,11 
 
 No. 2751. 
 
 C. F. Betting, Wehlheiden nr. Kassel. 
 
 Mechanical Workshops. 
 
 k 
 
 Exhibit: Analytical Balance for a charge of 200 grammes, 
 with mechanism for charging and discharging the weight pan without 
 opening the case. 
 
 By this mechanism substances may be- weighed quickly and accu- 
 rately and with ease. The substance which is to be weighed is placed 
 upon the pan on the left, the case is then closed and the weights are 
 placed upon the pan by simply turning the milled heads projecting on 
 the outside of the case. The latter remaining closed during the entire 
 operation of weighing, disturbances arising from changes of temperature 
 and currents of air are obviated. The weights, which range from 
 100 grammes to 1 centigramme, remain in the casing. Milligrammes 
 and fractional parts thereof are weighed by means of the riders. The 
 weight of the object having been determined by the mechanical weights 
 only a second set of weights is required for double weighing, the re- 
 spective weigths being introduced with opened case. The balance has 
 a sensibility of 0,1 milligramme. The beam is made of aluminium, the 
 other oscillating parts of thickly gilt brass. The planes are of carneol. 
 
 
 No. 2752. 
 
 Otto Bohne, Berlin S., 
 
 90 Prinzen-Strasse. 
 
 Aneroid -Barometers, Registering Barometers, 
 Thermometers and Hygrometers. 
 
 The Aneroid-Barograph which is shown in Fig. 1 at x / 4 full 
 size, is indisputably the most correct instrument for metereological ob- 
 servations. It indicates not only, like the ordinary barometer, the 
 height of the barometer at any particular moment, but also records 
 
12 
 
 Otto Bohne, Berlin S. 
 
 its movements continuously, noting, at the same time, day and hour. 
 These graphical records traced up.on a prepared strip of paper form 
 interesting material for future comparisons. 
 
 Fig. 1. 
 
 The new registering instruments, - - such as the barograph and 
 thermograph, which automatically record the position of the barometer 
 and thermometer with a degree of regularity and precision unattainable 
 by the most careful observer, render metereological observations very 
 little troublesome and thus also interesting to the lay public. The 
 low prices and simple manipulation of these instruments conduce to 
 increase their popularity and encourage the useful and interesting study 
 of weather prognostication. 
 
 Fig. 2 represents in Y 4 full size 
 of demonstration. 
 
 barometer for purposes 
 
Otto Bolmp. Berlin S. 
 
 13 
 
 The mechanism, which is exposed to view from all sides, is 
 isolated from the external atmosphere by a bell-jar. An india-rubber 
 tube is attached to the side and communicates with the interior of 
 the bell-jar. Barometric changes may be imitated by blowing into 
 the tube or withdrawing air through it, and the movements of the 
 mechanical parts produced by the rise and fall of the barometer may 
 be thus demonstrated and rendered intelligible to an audience. 
 
 Fig. 3 represents in 1 / 4 full size a holosteric barometer (Im- 
 proved Vidi-Barometer), which is specially adapted for metereological 
 observations. The Imperial German Navy has selected and adopted 
 exclusively this instrument from among the so-called metal-barometers. 
 The scale of this instrument is divided in l / 5 mm or Yio Engl. lines, as 
 preferred. By the mechanism the reading is magnified up to 23 times; 
 the fifth part of a millimeter of such a scale reads, therefore, as much 
 as 2 x / 3 mm. Accordingly, very fine measurements may even be made 
 with the naked eye. 
 
 The prices of the above instruments, also those of barometers 
 with altitude scale and metal - thermographs will be found in the 
 price-lists, which may be had gratis and post-free. 
 
14 Hilmar Bock, Oberwcissbach. Doerffel & Faerber, Berlin. 
 
 No. 2753. 
 
 Hilmar Bock, Oberweissbach m. Blankenburg 
 
 (Thuringia). 
 
 Gold Medal: Bruessels 1888. 
 
 Manufacturer of 
 
 Thermometers, Mercurial Barometers, Araeometers; Chemical, Physical 
 and Surgical Glass Instruments and Appliances, Artifical Eyes etc. etc. 
 
 No. 2756. 
 
 Doerffel & Faerber, Berlin NW., 
 
 44 Dorotheenstrasse. 
 
 Ophthalmological and Laryngological Instruments and 
 
 Appliances. Loring's, Knapp's, Keysets, Schweigger's, Hirsch- 
 
 berg's, Landolt's, Nachet's, Wecker's, Morton's 
 
 Ophthalmoscopes and others. 
 
 Trial spectacle cases, perimeter, Schweigger's hand peri- 
 meter, Horstmann's strabometer. 
 
 Laryngoscopes and Dentoscopes. 
 
 (The silver coating is protected by a galvanic deposit of copper 
 and is of special density.) 
 
 Illuminating Mirrors. 
 
 Illustrated catalogues may be had at the Exhibition or directly from the firm. 
 
Arth. Burkhardt, Glashtltte, Saxony. 
 
 15 
 
 No. 2754. 
 
 Arth. Burkhardt, Glashiitte, Saxony. 
 
 Civil Engineer. 
 First German Calculating Machine Works. 
 
 Established in 1878. 
 
 Silver Medal IX. Cincinnati Exhibition 1881. 
 
 Calculating machine with latest improvements and supplementary 
 types awarded several national prizes, gold and silver medals at home 
 and abroad, - - for addition , subtraction , multiplication , division 
 and calculation of powers, cubes and roots. 
 
 Absolute exactness and no mental fatigue! 
 
 Three sizes in most exact and elegant construction. 
 
 Size 1 
 
 factor N of 7 figures : Product M of 
 
 Size 2 
 Size 3 
 
 Factor of 6 figures 
 12 figures. 
 
 Factor, O of 8 figures X factor N of 9 figures: Product M of 
 
 16 figures. 
 
 Factor of 10 figures X factor N of 1 1 figures : Product M of 
 
 20 figures. 
 
 More than 500 machines have been supplied to all parts of the 
 world and given full satisfaction. 
 
 100 machines are being used in the principal offices of the U. S. A. 
 
 Representatives in the U. S. A.: 
 
 Keuffel & Esser Co., New York and Chicago. 
 
1(5 
 
 Georg Butenschoen, Bahrenfeld- Hamburg. 
 
 No. 2755. 
 
 Georg Butenschoen, Bahrenfeld m. Hamburg. 
 
 Mathematical and Mechanical Instrument Maker, 
 
 exhibits a Travelling Theodolite, an Inclinable Levelling Instrument 
 and a number of pocket instruments. It would lead too far were we 
 to attempt to give a detailed description of all the instruments made 
 by this firm. The Pocket Levelling Instruments, invented and patented 
 by the exhibitor, the speciality of the firm, may, however, be explain- 
 ed in a few words. 
 
 The instrument, which fits into a case and may be carried in the 
 pocket, is represented in the annexed illustration. It possesses the 
 special advantage that by its means, the spirit-level, cross-lines 
 and the object can be viewed simultaneously, the position of the 
 
 bubble of the spirit-level 
 not being, as is the case 
 with the usual instru- 
 ments, controlled exter- 
 nally, but, by means of 
 a mirror placed at an 
 angle of 45 between the 
 ocular and the cross- 
 lines, through the tele- 
 scope, where it is viewed 
 together with the object. 
 The image of the spirit- 
 level appears magnified 
 in the ocular, whereby 
 the exactness of the adjustment is greatly enhanced. The instrument,, 
 by this arrangement, attains, with due regard to its size, considerable 
 powers and greatly surpasses the water-level which is still extensively 
 used. The necessary manipulation is very simple, so that those, who 
 are not accustomed to work with the telescope level, will find no 
 difficulty in becoming familiarized with its use. 
 
 The business was begun on a small scale but rapidly worked 
 its way upwards. Mathematical and surveying instruments form the 
 principal objects of manufacture, but also nautical and astronomical 
 instruments are made. The instruments find a regular market in ail 
 European countries and meet also w y ith considerable demand in trans- 
 atlantic states. 
 
Bernhard Halle, Berlin. A. Hasemann, Berlin C. 17 
 
 No. 2760. 
 
 Bernhard Halle, Steglitz nr. Berlin. 
 
 Speciality: Optical appliances for polarization of light etc. 
 
 Preparations of Island double spar: Polarizing prisms. These 
 are made in numbers by a process invented by the exhibitor. By means 
 of a special sawing machine designed by Mr. Halle great accuracy of 
 the angle is obtained; by means of fine polishing appliances the surfaces 
 and angles are further reduced to absolute exactness; the prisms are of 
 the highest degree of perfection; nevertheless the prices are extremely 
 low and compete successfully with those of any other firm. 
 
 Beside these, quartz preparations of all kinds are made of the 
 highest perfection. Glass prisms without pyramidal errors, prisms 
 and plates of rock salt, alum, tourmaline etc., made in the most 
 accurate manner. 
 
 The trade supplied on liberal terms. 
 
 No. 2761. 
 
 A. Hasemann, Berlin C., 
 
 7 & 8 Nicolai Kirchhof 
 
 Maker of Balances. 
 
 This factory produces principally balances of best quality with 
 beams suspended in the center. 
 
 Exhibited balances: 
 1. A set of official assize balances Nos. i to 4. 
 
 Sensibility expressed according 
 
 No. Maximum charge to the directions of the German 
 
 Assize Department. 
 
 1 50 kilos 1/50000 
 
 2 5 1/20000 
 
 3 1 kilo 1/20000 
 
 4 20 grammes 1/4000 
 
 (These balances are among the instruments exhibited by 
 the Imperial Assize Commission.) 
 
 2 
 
18 
 
 A. Hasemann, Berlin C. 
 
 2. A machine for adjusting balances. Fig. 1. This machine 
 was invented in 1875 by H. Hasemann. It automatically adjusts the 
 parallelism of the knife-edges and the equidistance of the points of 
 
 suspension of the charges from the fulcrum. By means of a machine 
 of this description used in the factory since 1882 about 10000 balances 
 have been adjusted. 
 
 3. Drawing and description of: 
 ,,Oscillation of a cylinder upon another cylinder. " 
 
 (Knife-edge upon knife-edge). 
 'A new pendulum suspension by H. Hasemann. 
 The edge of a pendulum becomes, through pressure, reduced to 
 a surface. 
 
 The author has given this inevitably blunt edge a' cylindrical 
 
 form by a suitable grinding 
 machine and placed the 
 knife - edge thus protected 
 from further deterioration 
 upon a surface of similar 
 form. The horizontal pro- 
 jection a b of the travel of 
 C (the fulcrum) upon the 
 
 Fig. 2. 
 
 Fig. 3. 
 
 cylindrical surface of the pendulum is in the case of a plane = r sin a 
 
A. Hasemann, Berlin C. W. A. Hirschmann, Berlin N. 19 
 
 (fig. 2), in the case of a cylindrical surface = r (sin a sin- - j, (fig. 3). 
 
 - The section at the point of contact between a cylinder and a plane, 
 the line A B, (fig. 4), is, on account of the compressibilit}" of the 
 
 material, a curved line The existence of the components 
 
 shows that the fulcrum cannot be in A B. Rotation of the cylinder 
 
 Fig. 4. Fig. 5. 
 
 is, therefore, necessarily accompanied by a sliding movement along 
 A B and produces therefore friction. The forces, acting in the line 
 of contact of two similar cylindrical surfaces have, on the contrary, 
 no horizontal components, because, as fig. 5 shows, that path is a 
 straight line. A B represents therefore the fulcrum and rotation 
 takes place without friction. 
 
 No. 2765. 
 
 W. A. Hirschmann, Berlin, N. 
 
 1415 Johannisstrasse. 
 Manufacturer of Electro-Therapeutical Apparatus. 
 
 Established 1862. 
 
 1. Stationary Electro - Medical and Electrolytical Cabinet, 
 
 ^consisting of: 
 
 Galvanometer for absolute measurements, resistance box, induction 
 coil, pole reverser, cell numberer, commutator, influence machine and 
 all accessories for Franklinization. 
 
 2. Stationary Cabinet for electro-medical and electrolytical 
 purposes, illumination and galvanic cautery, arranged for connection 
 with an electric light installation of 110 volts. 
 
 The apparatus may be used simultaneously for illumination and 
 galvanic cautery, or for illumination and electrolysis etc., and is fitted 
 with all necessary appliances for connection with electric light installations. 
 
 3. Stationary Electro-Medical and Electrolytical Cabinet, 
 consisting of: 
 
 Galvanometer for absolute current measurements, pole reverser, 
 commutator, induction coil and cell numberer. 
 
 4. Stationary Cabinet for electro -medical and electrolytical 
 purposes, similar to No. 3, simple construction. 
 
20 W. A. Hirschmann, Berlin N. 
 
 5. Stationary Electro -Medical and Electrolytical Cabinet 
 designed for direct connection with an electric light installation of 
 110 volts. 
 
 6. Battery for Galvanic Cautery. 
 
 7. Apparatus for Illumination, for connection with an electric 
 light installation of not more than 110 volts. 
 
 8. Battery for Illumination. 
 
 9. Battery for Simultaneous Illumination and Galvanic Cautery. 
 
 10. Electro-Therapeutical Instruments: 
 
 Electrodes of all sizes, flexible electrodes for the ear, nose, larynx,, 
 stomach, rectum, bladder etc., electrodes for general faradization etc. 
 
 11. Portable Batteries for galvanic and faradic currents,, 
 with galvanometer for absolute measurements, cell numberer etc. 
 
 12. Portable Faradic Batteries in various sizes. 
 
 13. Portable Batteries for galvanic cautery. Portable batteries; 
 for illumination. 
 
 14. Galvanometers for absolute current measurements. These 
 galvanometers are perfectly aperiodical and conveniently portable. They 
 are equally well adapted for stationary and portable batteries. 
 
 15. Resistance Boxes, metallic and liquid resistances. 
 16. Electrolytical Instruments: 
 
 a) for the nose and larynx, 
 
 b) for the skin, 
 
 c) for gynaecological purposes. 
 
 17. Galvanic Cautery Instruments. 
 
 Snare Handles by Drs. Kuttner and Schech. Handles for 
 burners. Burners of any form. 
 
 18. Instruments for Illumination: 
 
 a) Head-band lamps for illuminating the nose, ear, larynx etc., 
 
 b) Prof. B. Fraenkel's stand for the same purpose, 
 
 c) Laryngoscope with mirrors, 
 
 d) Prof. Trautmann's lamp for the ear, 
 
 e) Translumination lamp for the frontal cavity, 
 
 f) Dr. L. Casper's urethral electroscope, also adapted for 
 the ear, nose and rectum, 
 
 g) Dr. Lohnstein's urethral translumination lamp, 
 h) Dr. Einhorn's stomachic translumination lamp, 
 
 i) Dr. Nitze's cystoscope for the illumination of the bladder^ 
 k) Dr. Nitze's irrigating cystoscope for the bladder, 
 1) Cystoscopic phantom. 
 
 Illustrated Price List. 
 
 Sole agents for the U. S. A. : 
 
 Messrs. Richard Kny & Co., 
 17 Park Place New York. 
 
Paul Bunge, Hamburg. 
 
 No. 2763. 
 
 Paul Bunge, (Propr. A. T. Herzberg) Hamburg. 
 
 13 Otto-Strasse. 
 Manufactory of analytical balances. 
 
 =: 
 
 Fig. 1. 
 
22 
 
 Paul Bunge, Hamburg. 
 
 1. Physical Balance for a Maximum load of 2 Kilos., 
 (Fig. 1) with Abbe collimator telescope, reflecting prism and concave 
 mirror fitted to the beam, which magnifies the oscillations of the latter 
 about 25 times. The beam is made of the finest argentan. In order to 
 reduce the effects of currents of air the pans are built up of 9 crosses. 
 By reason of the telescopic arrangement the oscillations are very ra- 
 pid and constant. All the knife-edges and planes of the beam and 
 pans are made of agate. 
 
 Length of beam 24 cm.; weighing space 17X32 cm. Degree 
 of sensibility: 5 degrees deflection in the telescope per milligramme., 
 or variable at will. The sensibility is constant for all charges. 
 Mounted on black glass or white marble plate. 
 
 Fig. 2. 
 
 2. Analytical Balance for a Maximum ^charge of 200 
 grammes (Fig. 2) with arrangement for mechanically charging or dis- 
 charging the weight-pan without opening the casing; with reading- 
 telescope. By means of sliding carriers having the values of the 
 respective weights marked on them each weight may be placed exactly 
 in the center of the pan, which consists of 17 concentric brackets 
 arranged one above the other; the mechanism is such that no vibra- 
 tion, friction or accidental dropping of weights can take place. By 
 turning a crank forward the frame supporting the carriers descends, 
 the carrier is liberated and may be withdrawn from under the weight. 
 The balance is thrown into action by turning the crank in the opposite 
 direction. As in this case the pointer swings out only one degree per 
 milligramme, the tenths of a milligramme may be read off in the tele- 
 scope directly and the hundredths may be estimated. The rapidity of 
 the oscillations has, therefore, in this balance been reduced in such 
 a way that it is to that of an equally sensible short beam balance 
 in the ratio of 1 : 1^10. The pan for the weighing charge is made 
 of rock-crystal. The rider slide is accurately notched on the dividing 
 engine. The pointer is of a triangular form to obviate vibration. 
 
 Length of beam: 13 cm. Sensibility: 0.05 mg. 
 
 Mounted on a clamped ma'hogony board or black glass plate. 
 
Paul JBunge, Hamburg. 
 
 23 
 
 Fig. 3. 
 
 3. Analytical Balance for a Maximum charge of 200 
 grammes. (Fig. -3.) Beam of finest argentan. All knife-edges of the 
 beam, suspensions and pans are made of agate. The rider-slide is 
 accurately notched by the dividing-engine, which precludes accidental 
 shifting of the rider. The pointer is triangular to obviate vibration. 
 The pans are made of rock-crystal and about 60 mm. (2 2 /V) in 
 diameter. Length of beam 13 cm; weighing space 9 X 20 cm. 
 
 Y 10 mg. deflects the pointer 1 degree with all charges. 
 
 Mounted on light or black glass or white marble plate. 
 
 Illustrated and descriptive catalogues (French and English) of 
 finest analytical, assay, vacuum and bullion balances etc. Gratis. 
 
 Gold Medals and Diplomas of Honour: 
 Vienna 1873. Hamburg 1876. Brussels 1888. Hamburg 1889. 
 
Jung, Heidelberg. 
 
 No. 2766. 
 
 R. Jung in Heidelberg, 
 
 12 Landhausstrasse. 
 Mechanician. 
 
 Gold Medals: Heidelberg 1870. Karlsruhe 1877." 
 
 Silver Medals: Mannheim 1880. Brussels 1888. 
 
 Diploma of Honour: Antwerp 1891. 
 
 Gold Medal. 
 
 Exhibits: 
 I. Micrological Apparatus. 
 
 1. Microtome for cutting large sections. New Model. 
 Mechanical knife motion and automatic vertical movement of object. 
 Appliances for cutting under liquid. 
 
 2. Thoma's Microtome No. I, length of bed 40 cm; object holder 
 fitted with two movable axes and with rack and pinion for vertical 
 adjustment of object; freezing apparatus; micrometer screw with 
 audible and adjustable catch; spirit irrigating apparatus (new pattern); 
 the necessary knives, knive supports etc. (Fig. 1). 
 
R. Jung-, Heidelberg. 
 
 25 
 
 W U V 
 
 Fig. 2. 
 
26 
 
 E. Jung, Heidelberg. 
 
 3. Thoma's Microtome No. II, length of bed 27 cm, with simple 
 object holder, simple micrometer screw, freezing apparatus, knives etc. 
 
 4. Thoma's Microtome No. II, equipped according to the directions 
 of the Zoological Station of Naples (Fig. 2). 
 
 5. Thoma's Microtome No. Ill, simple equipment, with movable 
 object holder, micrometer screw and knives. 
 
 6. Automatic Microtome for objects embedded in paraffine, with 
 endless transporting band for sections; capable of cutting sections 
 of 0.001 mm thickness (Fig. 3). 
 
 7. Small Microtome with mechanical knife motion, arranged as a 
 freezing and paraffine embedding microtome. (An extra-ordinarily 
 cheap instrument which commends itself for many purposes; (Fig. 4.) 
 Registered ! 
 
 8. Small microtome, similar to No. 7, with automatic feed. 
 
 9. A set of microtome knives and Instruments of nickelin and 
 platino-iridium for micrological purposes. 
 
 10. Microtome knife with longitudinal bore for cooling by water or 
 air (Fig. 5). 
 
K. Jung. Heidelberg. 
 
 27 
 
 11. Drying Oven, Heidelberg 
 pattern, large size, for sus- 
 pension from wall (Fig 6). 
 
 12. Water Bath for paraffine 
 embedding, Model of the Zoo- 
 logical Station at Naples 
 (Fig. 7). 
 
 , Fig. 7. 
 
28 R. Jung, Heidelberg. 
 
 13. Water Bath for paraffine embedding, similar to No. 12 but smaller. 
 
 14. Thermo-regulator, new design. 
 
 . Fig . 9. 
 
 Registered! (Fig. 8). 
 
 15. Dissecting stand with three low powers, with large bright and 
 black reflector. 
 
 16. Hones for setting microtome knives. 
 
 II. Physiological and Ophthalmologieal Instruments. 
 
 17. Foerster's Perimeter, new model (Fig. 9). 
 
 18. Pristley Smith's Perimeter (Fig. 10). 
 
 19. New Perimeter on adjustable stand (Fig. 11). 
 
 20. Helmholtz's Phacoscope for studying the changes of accomodation 
 in the eye. 
 
 21. Clock work for coloured discs, with set of discs, with speed 
 regulator and oscillating prism. New Model (Fig. 12). 
 
 22. Rotating Apparatus for three colour discs or for one disc of 
 30 cm diameter. New model. 
 
 23. Coloured papers and colour books. 
 
 24. Coloured transparent letters. 
 
 25. Rock crystal lenses. 
 
R. Jung, Heidelberg. 
 
 29 
 
 Fig. 11. 
 
 Fig. 12. 
 
R. Jung. Heidelberg. 
 
 Fig. 13. 
 
 26. Kuehne's Optical Eye (Fig. 13). 
 
 27. 
 28. 
 29. 
 
 30. 
 
 31. 
 32. 
 33. 
 3-4. 
 
 Knapp's Ophthalmotrope. (Fig. 14.) 
 Knapp's skeleton model. 
 
 O. Becker's Lens Models. A contribution to the history of the 
 development of the lens in the eyes of vertebrates and to the mor- 
 phology of the tissues in the lens of the human eye, with illustrated 
 description. 
 
 Model of the cornea and iris according to Weiss, with plano- 
 concave glass to reproduce the effect of the former and thus to 
 show its influence upon the apparent size and position of the pupil 
 (orthoscope). 
 
 Weiss's Gauge for measuring the distance of the pupils. 
 Sattler's and Nieden's galvano-cauterizer. 
 
 Electrodes for destroying the roots of troublesome hairs on the eyelids. 
 Pick's Ophthalmotonometer. 
 
11. Jung, Heidelberg. 31 
 
 35. Pristley Smith's lamp, improved by Leber, for lateral illumination 
 of the eye and for ophthalmoscopic examination, in particular, suitable 
 for use at the bed side. 
 
 36. Dr. Rindfleisch's Sciascope. 
 
 37. Dr. Weiss's Exophthalmometer. 
 
 Fig. 15. 
 
 38. Hering's small apparatus for testing binocular vision (Fig. 15). 
 
 Fig. 16. 
 
 39. Thoma's plates for studying the circulation of blood 
 
 a) in the mesentery and omentum of rabbits, dogs etc. (Fig. -16), 
 
 b) in the frog's tongue, (Fig. 17), 
 
 c) in the mesentery of the frog, 
 
 d) in the web of the frog, 
 
 e) in the lung of the frog. 
 
32 
 
 R. Jung, Heidelberg. 
 
 40. Thoma's drawing 
 apparatus, for low 
 magnifications and 
 reductions (1 to 10 
 diameters) , with 
 large field, drawing 
 paper on horizontal 
 plane (Fig. 18). 
 
 Fig. 17. 
 
 Fig. 18. Fig. 19. 
 
 41. Illuminating lens on stand, 10 cm diameter, with fitting for 
 placing coloured glasses before the lens. 
 
 42. Rotating double acting air pump for laboratory purposes, in- 
 jecting, air compressing, transmission of gases etc. Quick working 
 up to 125 cm of the mercury pressure gauge. (Fig. 19.) 
 
R. Jung', Heidelberg 1 . 
 
 Fig. 20. 
 
 48. Large Centrifuge, new design, 
 with 4 cylinders for hand or 
 engine power: in the latter case 
 a fly wheel mounted on tripod 
 stand is supplied with the ma- 
 chine. (Fig. 20.) 
 
 44. Small centrifuge, new design, 
 for high speeds (4000 to 6000 
 revolutions per minute) with co- 
 vered gearing and guard placed 
 over the cylinders, of which 
 there are 2 or 4 (Fig. 21, guard 
 not shown). 
 
 45. Helmholtz's model of the 
 mechanism of the auditory 
 organs (Fig. 22). 
 
 Fig. 21. 
 
R. Jung-, Heidelberg. 
 
 46. Model of the upper spinal cord and the oblongata, according 
 to the directions of Dr. Ludw. Edinger of Frankfort o/Main. This 
 model was completed in the spring of 1892 and agrees in all 
 
 Fig. 23. 
 
 particulars with the third edition of Edinger 's ,,12 Lectures on 
 the central nervous system". (Fig. 23.) 
 
 Illustrated Catalogue on application. Gratis. 
 
Max Kohl, Chemnitz. 
 
 35 
 
 No. 2769. 
 
 Max Kohl, Chemnitz, Saxony. 
 
 Scientific Instrument Maker. 
 Speciality: Physical Apparatus. 
 
 Trice list of 3000 Instruments and Appliances, in German, English? and French, 
 containing 1000 Illustrations to be had free on application. 
 
 Fig. 1. Bianchi Air Pump. 
 
36 Max Kohl, Chemnitz. 
 
 1. Bianchi Air Pump. (Fig. 1.) 
 This pump is double acting and fitted with Babinet cock. 
 
 The 
 
 cylinder being made of glass the piston is protected from oxydation,, 
 which cannot be avoided with metal cylinders. The valves are, in 
 contradistinction to older types, placed outside the barrel and are thus 
 easily accessible for the purpose of cleaning the pump. The air pump 
 is capable of producing an exhaustion of 2 mm mercurial pressure gauge. 
 The plate is fitted with electrodes communicating with the interior of 
 the recipient. 
 
 Fig. 2. 
 
 2. Deleuil Air Pump. (Fig. 2.) 
 
 The metal piston works very easily in the glass barrel. The pump 
 is double acting and may be used both as an exhausting and com- 
 pressing pump. It is capable of producing exhaustion of 2 mm mercurial 
 pressure gauge. 
 
Max Kohl. Chemnitz. 
 
 37 
 
 
 3. Helmholtz's Double Syren. 
 
 (Fig. 3.) 
 
 The double syren is particularly 
 adapted for ascertaining the number 
 of vibrations producing certain notes 
 and for experiments on harmonics, 
 beats and combination notes. The 
 ratch of the train of wheels is fitted 
 with electrical contact which con- 
 nects it with an electrical second 
 pendulum clock. 
 
 4. Timing Apparatus for 
 producing Lissajous' Curves. 
 
 (Fig. 4.) 
 
 r ^ The tuning forks have excellently 
 ground and polished steel mirrors 
 attached to their limbs and one of 
 the forks is intoned by electro-mag- 
 netic means. The following acces- 
 sories are supplied with the apparatus. 
 2 tuning forks in C = 256 oscilla- 
 tions, 
 
 1 F = 170 2 / 3 
 1 = 512 
 
 The apparatus is very suitable 
 for demonstration on the screen. 
 
 5. Portable Reflecting Galvanometer with Ocular Scale according 
 to Prof. Weinhold. (Fig. 5.) 
 
 The ocular of the telescope attached to this instrument is provided 
 with a transparent scale. A small mirror placed at the side of the 
 ocular throws a pencil of light upon a reflecting prism fixed to the 
 scale whence it passes to the telescope objective. The telescope is 
 
38 
 
 Max Kohl, Chemnitz. 
 
 made up of two parts which are at right angles to each other, a rectan- 
 gular reflecting prism being placed between ocular and objective 
 
 at the point of intersection of the 
 axes. The light reflected by the small 
 prism in the oculnr parses through the ob- 
 jective and meets the mirror attached to 
 a semicircular or annular magnet : it is- 
 then reflected by this mirror and returns 
 to the ocular. The image of a cross line 
 placed below the small reflecting prism 
 is in this manner thrown upon the ocular 
 scale and the slightest movement of the 
 mirror rendered visible. The sensibility 
 of this instrument is exceedingly great 
 and may be regulated to a certain extent 
 according to the requirements of the case 
 by means of two controlling magnets. 
 When adjusted for maximum sensibility 
 a deflection of one division of the scale 
 represents about 0.00000018 Amp. r 
 when adjusted for its minimum sensibility 
 0.0000013 Amp. The galvanometer is 
 exceedingly portable, being provided 
 with a most effective disengaging catch 
 and having all its sensitive parts well encased 
 and protected. The galvanometer is, therefore, 
 principally used for testing cables and insu- 
 lations, and is unquestionably the best existing 
 instrument for this purpose. 
 
 6. Beetz's Lecture 
 Galvanometer. (Fig. 6.) 
 
 This galvanometer is made in 
 a most convenient form for lecture 
 demonstrations. It is provided 
 with a controlling magnet so as 
 to render it possible to always 
 direct the scale towards the au- 
 dience and its scale is divided so 
 as to be distinctly visible from 
 the distance. A special feature 
 of the instrument is the facility 
 with which the coils can be inter- 
 changed. Two differently wound 
 coils are supplied with the in- 
 strument. 
 
 Fie;. 6. 
 
Max Kohl, Chenmitz. 
 
 39 
 
 7. Wiedemann's Reflecting Galvanometer. (Fig. 7.) 
 
 This galvanometer lias been designed to meet the requirements 
 of laboratories. It is provided with bell and ring magnet, spherical 
 
 Fier. 
 
 copper damper and adjustable damping plates. The coils may be jt ined 
 
 up according to requirement. 
 
 Accessories : 
 
 2 coils of 4 X 500 = 2000 convolutions of thin wire, 
 2 2X250= 500 , stout 
 
40 
 
 Max Kohl. Chemnitz. 
 
 8. Biihmkorff 
 Induction Coil giving 
 500 millimeter 
 sparks. (Fig. 8.) 
 The insulation in the 
 secondary coil consists 
 of a soft material which 
 obviates the risk of de- 
 struction during trans- 
 port. The length of the 
 secondary wire is about 
 75000 meters. The 
 apparatus is provided 
 with a Foucault contact 
 breaker and 2 spark 
 electrode stands fitted 
 with wire clamps for 
 spectroscopic experi- 
 ments. 
 
 9. Electromagnet 
 for Diamagnetic and 
 
 Paramagnetic 
 Experiments. (Fig. 9) 
 
 Accessories : 
 
 Suspension apparatus 
 for light paramagnetic 
 and diamagnetic bodies, 
 in glass .box. 
 
 Apparatus for de- 
 monstrating the dia- 
 magnetism of flames. 
 
 Apparatus for de- 
 monstrating the damp- 
 ing effect of induction. 
 
 Polarimeter showing 
 the rotation of the po- 
 larization plane. 
 
 Copper disc for Fou- 
 cault's currents. 
 
 Apparatus for sepa- 
 rating aureole and 
 sparks. 
 
 10. Miniature Steam Engine and Boiler encased in a nut shell. 
 
 (Fig. 10.) 
 
 The annexed figure is a full sized illustration of the engine. 
 The model has been made in the workshops of the firm and forms 
 
Max Kohl, Chemnitz. 
 
 41 
 
 skill. The following are the di- 
 
 iff. 9. 
 
 an interesting example of delicate 
 mensions of the engine: 
 
 Length of cylinder 
 
 Internal diameter of cylinder 
 
 Diameter of fly wheel . 
 
 AVidth of fly wheel 
 
 Length of boiler 
 
 Diameter of boiler 
 
 Bore of steam inlet pipe 
 
 Length of slide valve .... 
 
 Width of slide valve 
 
 Length and width of steam ports respectively: 1.3 and _ 
 
 Yet this engine is fitted with safety valve, water inlet and outlet 
 Watt regulator and water gauge. 
 
 o.o mm 
 
 2 
 
 10 .. 
 
 1.5 
 
 20 
 
 8.5 
 
 0.4 
 
 1.8 
 
 1.7 
 0.2 
 
42 
 
 A. Kruss. Hamburg. 
 
 No. 2770. 
 A. KrilSS (Principal Dr. Hugo Kriiss). Hamburg. 
 
 7 Adolphsbrucke. 
 Optical Works. 
 
 Large Automatic Spectroscope with 6 Prisms ; with dispersion 
 of 32 degrees; with fixed telescope. Original Construction. (Fig. 1.) 
 
 In spite of the movement of the prisms, which is necessary to obtain 
 the minimum of deviation for the various rays of the spectrum, the dispersion 
 between the red and violet rays being 82 degrees, the telescope remains fixed 
 and, therefore, also the eye of the observer. This is attained by an ingenious 
 mechanism, and the use of a central mirror. The spectrum may be made to 
 traverse the field, either quickly by hand or slowly by means of a micrometer- 
 screw, which also serves for measuring the distances between the spectrum lines. 
 
 Automatic Spectroscope with 6 Prisms, with dispersion of 
 32 degrees. Original Construction. (Fig. 2.) 
 
 The automatic adjustment of the prisms is effected by a new ingenious 
 mechanism, which acts with greater ease and precision than those hitherto used. 
 The vertical axis a, which is fixed in the center of the prism stage, bears six 
 sliding and rotating rings, each of which is connected to one of the six prisms. 
 The collimator 8 and the telescope B have reflecting prisms placed before 
 
A. Kriiss, Hamburg. 43 
 
 their objectives, both tubes being thus directed to the axis of the instrument. 
 By means of the rod s the telescope may be connected with the mechanism 
 
 Fig. 2. 
 
 behind any of the prisms and thus any number of the latter may be put into 
 action. The apparatus admits, therefore, of working with different dispersive 
 powers.- 
 
 Universal Spectroscope of Original Construction, for Spec- 
 trum Photometry, Qualitative and Quantitative Analysis. (Fig. 3.) 
 
 This universal spectroscope is most suitable for physical and chemical 
 laboratories and can be applied for all purposes of physiological chemistry. 
 For qualitative analysis it is fitted with scale tube and simple micrometer slit. 
 With divided drum, platinum lips, comparison prism- and lamp for illumination 
 of scale. For quantitative analysis and photometry of the absorption spectra it 
 is fitted with a micrometer double slit with two divided drums (one of these 
 with vernier) and Yierordt's symmetrical ocular slit, absorption vessel with 
 parallel sides and Schulz's glass body, stand with micrometer adjustment for 
 the latter and lamp for observation. 
 
 The Universal Spectroscope is fitted with a flint glass prism of 60 and 
 a triple Rutherford prism; these being interchangeable the apparatus may be 
 worked with low or high dispersion. 
 
44 
 
 A. Kriiss, Hamburg. 
 
 The telescope is moved by means of a micrometer screw and the amount 
 of movement is read off a divided drum; also the width of the ocular slit and 
 the travel of the cross lines can be measured bv means of a divided drum. 
 
 Fig. 3. 
 
 The slit, by a very simple arrangement, opens symmetrically with respect 
 to the optical axis. 
 
 C. H. Wolff's Colorimeter. (Fig. 4.) 
 
 This instrument is intended for colorimetric 
 determination of the concentration of coloured 
 liquids by comparison with a standard solution. 
 The light is, by means of a mirror placed below 
 the measuring cylinders, reflected through the 
 latter, and, by means of two reflecting prisms, 
 the two pencils are made to illuminate the two 
 halves of the field of a lens. From the darker 
 liquid as much is allowed to flow off as is ne- 
 cessary to render both halves of the field equally 
 bright. The respective concentrations of the li- 
 quids are than in the inverted ratio of the heights 
 of the liquid columns. 
 
 This colorimeter may be used for all colo- 
 rimetric tests in analytical chemistry, e. g. for 
 determining the percentage of ammonia in water, 
 for examination of nitrous acid, for selecting 
 colours or salicilic acid, for quantitative deter- 
 mination of slight admixtures of copper, zinc, 
 chlorine compounds etc. 
 
A. Kriiss, Hamburg. 
 
 45 
 
 Polarization Colorimeter. Original 
 
 construction. (Fig. 5.) 
 
 A peculiar combination of polarizing prisms with 
 a double quartz plate greatly increases the exactness 
 which is attainable with the colorimeter as ordinarily 
 constructed. For in this case not only the brightness 
 but also the colour of the illuminated halves of the 
 field have to be equalized. 
 
 Browning's Pocket - Spectroscope with 
 A triple prisms. 
 
 Browning's Pocket -Spectroscope, with 
 quintuple prisms. 
 
 H. W. Vogel's Pocket - Spectroscope,. 
 
 with mirror arrangement for comparison-spec- 
 trum, and with tube holder. 
 
 H. W. Vogel's Pocket - Spectroscope, 
 
 with universal stand, burner, bottles etc.; in case. 
 
 Lummer and Brodhun's Photometer. (Fig. 6.) 
 
 Fipr. 6. 
 
46 A. Kriiss. Hamburg. 
 
 The Scale has a length of 3 meters (9' 10"), it is divided in half 
 centimeters. If desired also a scale of intensity measures may be added. 
 
 By the arrangement of Luminer and Brodhim's photometer the images 
 of the two sides of the screen, which are perfectly similar, are reflected 
 in such a manner that the image of one side appears as a disc completely 
 encircled by the image of the other disc. These differences in the intensity 
 are indicated by a distinct line: with equal intensities this line must disappear. 
 
 Bunsen's Photometer revolving on a divided circle, for 
 measuring the intensities corresponding to different angles of emission. 
 
 Photometer Mirror with divided circle. 
 
 It is inclined at 45 to a horizontal axis and is intended for photometric 
 evaluation of the intensities of light emitted in different directions by fixed lights. 
 
 Fig. 7. Fiff. 8. 
 
 Photometric Stand for Incandescent Lamps. (Fig. 7.) 
 The incandescent lamp revolves on two axes at right angles to 
 one another and its position may be read off. 
 
 Optical Flame Gauge. Original Construction, for accurately 
 measuring the length of a flame of a candle or other light. (Fig. 8.) 
 
 (Hefner's) Amyl-acetate lamp with optical flame gauge. 
 Beside these instruments the following instruments made by this firm are 
 being exhibited in other departments: 
 
 Spectroscope and Colorimeter, which will be found among the 
 apparatus composing the Hygienic Laboratory exhibited by the Hygienic 
 Institute of the University of Berlin. 
 
 Projection Apparatus and Lantern Slides forming part of the 
 Educational Appliances, exhibited by the Prussian Ministry of Public Instruction. 
 
G. Lufft, Stuttgart. 
 
 47 
 
 No. 2772. 
 G. Lufft, Stuttgart (Germany). 
 
 Metal Barometer Works. 
 
 Largest Establishment for the manufacture of Metal Barometers. 
 
 These works were founded in 1880 and are exclusively engaged 
 in the manufacture of metal barometers, of which many thousands are 
 exported annually to all parts of the world. The firm exercises its 
 utmost endeavours in adapting the barometers with greatest possible 
 exactness to each particular purpose. The exhibits are intended to 
 show to what extent these endeavours have been attended by success; 
 nearly all the different kinds of these barometers are represented in 
 two groups. 
 
 Ornamental Barometers. 
 
 These are made in any size and style, for hanging and standing, 
 in metal cases and wood frames, with and without thermometers, and 
 form in these days a most important item in domestic decoration. 
 
 To satisfy all requirements they are made in all sizes varying 
 from the smallest suspending barometers of 3 / 4 inch diameter dial to 
 large barometers of 3 feet diameter for public places, railway stations, 
 shop windows etc. 
 
 The mechanism yields very large and exact indications. 
 
48 G. Lufft, Stuttgart. 
 
 Scientific Barometers, 
 
 These barometers ,are made in three sizes, viz. with dials of 45 mm 
 (l a / 4 inch), 80 mm (3 inch) and 130 mm (5 inch) diameter. The latter 
 are fitted with fine leather sling cases. 
 
 These instruments are made with the greatest care and accurately 
 compensated , so as to render their indications independent of changes 
 of temperature. 
 
 In order, however, that they may in this respect be tested at any 
 time, each barometer is provided with a thermometer, which is fitted 
 inside the casing upon the dial; the leather case also is fitted with a 
 thermometer for determining the temperature of the external atmosphere 
 surrounding the instrument. 
 
 The dials of these barometers are silvered and are, according to 
 the purpose which the instrument is to serve, graduated in l / 2 , Vi anc ^ 
 2 /i millimeter or Y 60 , 1 / 24 and Yi2 inch: if desired they are also pro- 
 vided with so-called ,,orometric'' divisions, i. e. divisions for directly 
 reading altitudes of 1800 m (5300 feet), 2600 m (9000 feet), 5000 m 
 (16500 feet) and 8500 m (28200 feet). 
 
 These instruments may in the simplest manner be used for sur- 
 veying purposes, by engineers, explorers and aeronauts. 
 
 Self -registering Barometers, 
 
 which save meteorologists the time wasting trouble of having to read 
 the barometric indications, so that he has to insert the prepared strip 
 of paper into the instruments and to wind up the clock work once a week. 
 These instruments are compensated, extremely solid and made 
 with great precision. They accurately mark the position of the baro- 
 meter every 15 or 20 minutes within Yio millimeter. 
 
 25 different kinds of 
 
(i. Lufft, Stuttgart. Jacob Merz, Miinchen. 49 
 
 Watch Form Barometers 
 
 are made to supply the "wants of tourists. They are made in a great 
 variety of forms and prices. 
 
 The best proof of the excellence and popularity of these instru- 
 ments is furnished by the increasing 'demand for them and the repeated 
 extensions of the works thereby occasioned. To these proofs of excellence 
 may be added numerous testimonials from universities, meteorological 
 institutes, engineers and others. 
 
 The ornamental barometers are only supplied to dealers and export 
 merchants: the scientific barometers are also sold, according to special 
 price lists, to private users. 
 
 Each barometer is marked with the trade mark shown above. 
 
 No. 2773. 
 
 Jacob Merz, Miinchen, 
 
 31 Blumenstrasse. 
 Optical Works. 
 
 Description of the Exhibits: 
 
 1. Equatorial (Refractor) having an objective of 6 inches effect- 
 ive aperture and a focal length of 65 3 /4 inches. Provided with a 
 rotating finder having an aperture of 19 lines and 11 inches focus; 
 fitted with erecting ocular; magnifj'ing 8*/a times. 
 
 The instrument rests upon an iron tripod and is fitted with base 
 screw r s and wheels. It is adapted for low and high positions; it can 
 be levelled and has adjustable polar altitude of to 60. Rectascen- 
 sion and declination circles divided on silver. The former divided, in 
 Vi minutes and reading by verniers to 2 seconds. The latter divided 
 in 15 /i minutes and reading by verniers and lenses to 30 seconds. 
 
 The instrument is also provided with azimuth adjustment the 
 circle being divided on brass in 1 /.-> degrees. 
 
 4 
 
50 Jacob Merz, Miiuchen. 
 
 The instrument is fitted with clock work (which may be correct- 
 ed for stellar and solar time). It is supplied with 7 astronomical 
 oculars (5 Huyghenian, 2 erecting) magnifying 26, 39, 88, 99, 132, 
 198, 330 times. The magnification is capable of increase beyond 
 these figures. Cross line micrometer with fine measuring screw and 
 position circle divided on silver in 1 / i degrees, reading to minutes, 
 with field and cross line illumination, supplied with 6 micrometer 
 oculars magnifying 66 to 330 times. With the instrument are sup- 
 plied a helioscope and an universal spectroscope. 
 
 The instrument being adjustable for either hemisphere and being 
 very portable is adapted for scientific purposes. 
 
 2. Equatorial (Refractor) having an objective of 5 inches 
 diameter and a focus of 70 inches', provided with a finder having an 
 objective of iVa inch diameter and 11 inches focus, with erecting 
 ocular, magnifying 8 l /2 times. The instrument rests upon an iron 
 tripod fitted w r ith levelling screws and wheels and is adapted for a 
 high or low position and has also adjustable polar altitude of to 
 60. Eectascension and declination circles with divisions on brass, 
 the former reading to 10 minutes and reading by verniers 1 minute; 
 the latter divided in Vi degrees and reading by verniers to 5 minutes. 
 The instrument is provided with all coarse and fine adjustments and 
 also with azimuth adjustment without circle. The instrument is sup- 
 plied with 1 terrestrial ocular, magnifying 80 times and 6 astrono- 
 mical oculars (5 Huyghenian and 1 erecting ocular) magnifying 41, 
 93, 105, 140, 210, 350 times and capable of higher magnifications. 
 
 If desired the following may be added: Micrometer with double 
 and single steel ring, helioscope and spectroscope. 
 
 3. The following ten Objectives: 
 
 1 objective of 11 inches effective aperture and 120 inches focus. 
 
 1 9V 2 * , H7 
 
 1 , 7 98 
 
 4 ,,6 91,83,76,66 
 
 3 ,,5 64, 60, 59 
 
 Refractors and objectives of larger dimensions than those named 
 are made in the most exact manner to order. Beside these the esta- 
 blishment produces various other optical instruments. It exports to 
 all parts of the globe. 
 
Oscar Moeller, Hamburg. 
 
 51 
 
 No. 2774. 
 
 Oscar Moeller in Hamburg, 
 
 73 Vale 11 tin skamp. 
 Steam Factory of Holosteric and New Patent Metallic Barometers. 
 
 Lapp manufacture 
 
 Holosterie 
 
 and 
 
 New Patent Baroieters. 
 
 New Patent Compensation 
 Plate Thermometers 
 
 (metal-index) 
 and 
 
 Contact-Thermometers. 
 
 of 
 
 Surgical Instruments. 
 
 U.S.A. No. 459977. 
 
 German Empire No. 59774. 
 
 England No. 18300. 
 Silver Medal, Hamburg 1889. 
 
 France No. 213561. 
 Silver Medal, Melbourne 1880. 
 
 _.f8 89 
 
 Highest Award. 
 
 Highest Award. 
 
 Established 
 1877- 
 
 20000 Metall. Barometers and Thermometers manufactured annually. 
 
 Telegraphic afltes: 
 
 Oscar Moeller, Hamburg, 
 
f>2 Oscar Moellor, Hamburg. 
 
 Barometers at all prices, of any desired finish and style 
 of framing from the very plainest up to the most elegant master- 
 pieces of wood carving. 
 
 The Patent Barometers, manufactured exclusively by Oscar 
 Moeller, are cheaper than any other type and, besides, excel in the 
 following points: 
 
 1. Accurate working and great sensibility, the slightest variation 
 of atmospheric pressure being at once rendered apparent, there 
 being no dead movement to absorb it as is the case with com- 
 plicated lever work;' 
 
 2. absence of so called ,,back lash", which is inavoidable in a 
 complicated mechanism ; 
 
 3. but very little occasion for repairs, none of the parts being 
 exposed to breakage; the instruments are thus capable of re- 
 sisting shocks and falls and are, in particular, suitable for 
 shipment abroad; 
 
 4. absence of back or forward movement of the index, which is 
 a common feature with the more complicated instruments: 
 
 5. elegant appearance of the entire visible mechanism: 
 
 6. great lightness in weight effecting great saving of freight 
 and postage. 
 
 Dials engraved in the following languages: German, English, 
 French , Italian , Spanish , Portuguese , Dutch , Danish , Norwegian, 
 Swedish, Bohemian, Polish, Croatian and Russian. 
 
 Sizes of Dials: 80, 95, 115, 130, 180, 260 mm diameter; 
 sizes 95, 115, 130, 180, 260 mm diameter may also be had fitted 
 with adjustable glass scales. Glass scale barometers are provided 
 w r ith silvered or finely enamelled insides. 
 
 Paper Dials, adjustable, are supplied gratis on application. 
 Firms' names on paper dials supplied gratis; if on glass dials 40 Pf. each. 
 
 Price lists in German and English and Book of illustrations 
 free of charge on application. 
 
 Patent Compensation Plate Thermometers (metal - index), 
 in which, after the manner of barometers, the pointer indicates the 
 temperature, in lieu of atmospheric pressure, on a graduated dial, 
 are supplied mounted in all kinds of frames forming elegant orna- 
 ments and useful companions to barometers. They are also supplied 
 in the form of contact thermometers adjusted to sound a bell so as 
 to indicate rise or fall of temperature beyond certain given limits, 
 e. g. the thermometer may at will be set to signal 10 as the lower 
 limit of fall and 20 as the upper limit of rise of temperature. 
 
 The barometers manufactured by this firm are of the greatest 
 sensibility and are warranted to indicate correctly. The exhibits in- 
 clude barometers of a great variety of prices and styles of frames 
 from the plainest wood to artistic wood carving, also barometers with 
 
Oscar Moeller, Hamburg. W. Niehls, Berlin N. 53 
 
 coloured dials of paper and glass, nickel plated mechanism and silver 
 plated or enamelled insides. Barometers in metal cases. New 
 Patent Compensation Plate Thermometer (metal-index), by which read- 
 ings of the temperature may be taken at a distance, a great advan- 
 tage as compared with mercurial thermometers. Contact thermometers 
 of similar construction with one or two indices which may be adjusted 
 to sound a bell at any desired temperature. And a large Maximum 
 and Minimum Compensation Plate Thermometer. 
 
 Particular attention is drawn to the Pocket Altitude Barometers. 
 
 The great cheapness of these instruments is mainly due to the 
 employment of about 50 machines specially constructed for their ma- 
 nufacture. 
 
 No. 2776. 
 
 W. Niehls, Berlin N., 
 
 160 Schimhauser- Alice. 
 Maker of Meteorological and Physical Instruments. 
 
 Glass Fusion Scale. Registered. For determining the degree 
 of fusibility of different glasses; with directions for using, in case with 
 test rods. Suitable for glass works, chemical and physical laboratories 
 and for teaching purposes etc. 
 
 High Temperature Thermometers, /Jena glass 59 m , indicating 
 to 550 C. Graduation burnt into glass by patent process. This pro- 
 cess not only adds to the permanency of the colour of the division 
 lines but also increases the durability of the thermometers. 
 
 Rod Thermometers with graduation burnt in or first etched 
 and subsequently burnt in, by the above process. 
 
 Thermometers for clinical purposes. Mineral Oil Tester, 
 according to the directions of the Imperial German Standard 
 Assize Commission. 
 
 Breguet's Metallic Thermometer, for class demonstration. 
 
54 
 
 Albert Ott, Kempten. 
 
 No. 2777. 
 
 Albert Ott, Kempten, Bavaria. 
 
 Mathematical and Mechanical Instrument Works. 
 
 Established in 1873. 
 
 Awards: Melbourne 1880; Madrid 1883; Graz 1890; Brunswick 
 Nuremberg 1882; Augsburgh 1886. 
 
 The whole of the * exhibits have originated in these works. 
 
 1881; 
 
 1 . 1 Pantograph (Fig. 1) with limbs 84 cm long of nickel-plated brass- 
 tubing, adapted for reductions and enlargements of all ratios from 1 : 20 
 to 1:1. With lead pencil, puncturing pins and glass-marker with lens. 
 Shown in the illustration with pole in the center; ratio 1:1. Set up 
 with pole at end; ratio 1 : 2 or 2 : 1. 
 
 Fig. 1. 
 
 (In the German University Exhibition a similar pantograph will 
 be found which has been set up with its pole in the center; ratio 1 : 1) 
 
 Of these pantographs, which excel in exactness and handiness, 
 over 600 have been supplied to all parts of the world. 
 
Albert Ott, Kempten. 
 
 55 
 
 2. 1 Planimeter, arranged for a fixed ratio of 1 : 1000 (metric 
 system) only. 
 
 3. 1 Planimeter (Fig. 2) with adjustable tracing-lever and needle- 
 pole, with guide-ruler, adjustable for any measure or any ratio, also suitable 
 for computing indicator-diagrams. The wheel has a circumference of exactly 
 66 mm; the tracing-pin and the pole-axis have at their ends points 
 for fixing the basis of the diagram. Each division read off by vernier 
 on the wheel represents 0,15 m (mean ordinate of the diagram). 
 
 4. 1 Planimeter with adjustable tracing-lever, suitable for all 
 measures and ratios. With pole weight and controlling surface; with 
 glass wheel. 
 
 AVith all these planimeters the wheel has for the last 10 years 
 been supplied with the divisions marked on celluloid; the adjustable 
 tracing-lever is provided with scale, vernier and pointer for adjusting 
 the required ratio. The wheels are usually made of steel, only if 
 specially desired they are made of glass. Over 1000 of these instruments 
 have been supplied. 
 
 Fig. 3. 
 
 5. 1 Current meter (Fig. 3), smallest size, with counting wheels 
 for 800 revolutions; attachable to a wood plank; dissectable; in pocket 
 folding case; pitch of vanes 0,15 m. 
 
 6. Current meter, medium size, with counting wheels for 2000 
 semi-revolutions. The propeller spindle runs in agate bearings; the 
 instrument is provided with mechanical releasing and fixing gear, with 
 pulley and clamp for vertical movement along an iron slotted tube. 
 Pitch af vanes 0,3 m. 
 
 7. Current meter, large size, with electrical transmission of the 
 revolutions to bell and speed indicator may be raised and lowered along 
 a fixed vertical rod; suitable also as a floating vane for showing rate of 
 flow of surface-water. Pitch of vanes 0,50 and 1 -m. 
 
 (The instruments Nos. 6 and 7 have been constructed according to 
 the directions of Prof. A. R. Harlacher of Prague.) 
 
56 
 
 Albert Ott, Kempt on. 
 
 8. 1 Hanging Circumferenter for geological and mining purposes, 
 collapsible; in leather sling-case. 
 
 9. 1 Compass Instrument with telescope for measuring distances, 
 level, azimuth and altitude circles reading to 1'; stand with ad- 
 justable legs. 
 
 10. A small Theodolite (Universal instrument) with brass ., tele- 
 scope" stand; packing in small case. 
 
 11. 1 Universal Levelling Instrument. 
 
 Fii?. 4. 
 
Albert Ott, Kempten. > 57 
 
 12. A Theodolite (Tacheometer) (Fig. 4), latest construction, 
 Patented in Germany to the inventors, Messrs.Tichy and Ott; particu- 
 lary suitable for accurate and speedy work in land-surveying. 
 
 The circles are divided on the 360 degrees system, but do not read 
 to minutes and seconds, but to -y^y degrees. Distances are measured, 
 by a new method, by means of a staff divided in logarithmic progression, 
 which has to be set up strictly vertical, two supports and crossed levels 
 being appended for this purpose. 
 
 By this method distances are measured much more exact!}* than 
 is possible with other optical distance measuring instruments. 
 
 In order to find from the slanting distance the horizontal distance 
 the altitude arc has, beside the ordinary graduation, logarithmic divisions. 
 By subtracting the altitude reading from the height on the staff the 
 reduced distance is directly obtained from ordinary tables of logarithms, 
 .and from this and the altitude the difference of elevation .between the 
 instrument and the stand-point of the staff can be found. 
 
 13. A Theodolite similar to No. 11, but with rotating azimuth 
 and altitude circles, either reading by micrometer and lens, to Viooo de- 
 .gree on the 360 circles. 
 
 A noticeable feature of the theodolites Nos. 11 and 12 is the form 
 of the stands supplied with them and the manner of packing the instruments 
 in the case. 
 
 14. A logarithmic staff for Nos. 11 and 12. These staves are 
 made of lengths of 2.05, 2.55 and 3.05 meter for distances of 200, 250 
 and 300 meters respectively. 
 
 15. A Surveyor's Drawing Board with table, Patented in 
 Germany to the inventors, Messrs. Tichy and Ott, for drawing with 
 accuracy and despatch tacheometric measurements made with the theodolite. 
 The angles may be drawn either to sexagesimal minutes or centesimals 
 of the 360 degree or 400 grade system. The distances are marked by 
 means of a puncturing-needle which slides along the divided ruler and 
 the points are encircled by means of a rotating lead pencil. 
 
 (A detailed description of this apparatus will be found in the 
 catalogue of the Exhibition of the German Universities.) 
 
58 
 
 A. Pessler, Freiberg. Reiniger, Gebbert & Schall, Erlangen. 
 
 Xo. 277S. 
 
 A. Pessler, Freiberg (Saxony). 
 
 Mechanician. 
 
 Four levels, 275 mm long, with air-chamber and double row of 
 numbers. The degree of sensibility (1 2 sec.) will be found marked at 
 the side of each level. 
 
 Four reversible levels, one with air-chamber (5 8 sec). 
 
 The whole of these levels are made of the best hard-glass suitable 
 for this purpose; they are filled with purest sulphuric aether and tested 
 on an apparatus with exact screw. 
 
 Over 20000 ground levels (1 GO sec.) have been supplied. 
 
 Price-lists to be had of the Agent in the Collective Exhibition. 
 
 'No. 2779. 
 
 Reiniger, Gebbert & Schall, Erlangen (Bavaria). 
 
 Manufacturers of Electro -thefapeutical Appliances. 
 
 30 Ziegelstrasse, 
 Berlin. 
 
 Awarded 12 first 
 and Commendations 
 
 Established 
 
 BRANCHES: 
 
 43 Alserstrasse, 
 
 Vienna VIII. 
 
 55 AVigmore Street. 
 London W. 
 
 Medals, Diplomas 
 at various exhibitions. 
 
 in 1876. 
 
 Represented at the Exhibition by the Electrical Engineer to the 
 firm, Mr. Ottomar Carliczek, Chicago. (Mr. Carliczek's business and 
 private address is notified at the Exhibition stand). 
 
 The works include: Mechanical fitting shops, screw turning, milling, joiner's 
 polishing and nickel plating shops, with steam power supply. 
 
 Exhibits: 1. A Stationary Apparatus for Galvano-Faradisation, 
 in elegant walnut case with glass cover and desk shaped top, with 40 
 
Reiniger, Gebbert & Schall, Erlangen. 59 
 
 Leclanche cells, Barbier's type, fitted with Patent Double Crank 
 Commutator and Dr. Brenner's horizontal pole reverser with variable 
 periodicity. Horizontal galvanometer with fibre suspension reading up to 
 5 milliamperes, with two shunt circuits, Dr. Ziemssen's rheostat of 
 nickelin wire up to 5000 ohms; Prof. Du Bois-Reymond's Induction 
 apparatus with Meyer's adjustable current breaker, switch for induction 
 battery of 4 cells, commutator for primary and secondary current, with 
 accessories. 
 
 2. A Leclanche Medical Battery with stopper connections, con- 
 sisting of 24 hermetically sealed cells, in oak box with leather handle 
 (simplest design). 
 
 3. A Leclanche Medical Battery, consisting of 30 hermetically 
 sealed cells, simple crank commutator and pole reverser, in oak box. 
 
 4. A Leclanche Double Apparatus, consisting of 24 hermeti- 
 cally sealed cells, simple crank commutator, pole reverser and 
 Spamer's induction apparatus in oak box. 
 
 5. A Leclanche Battery, consisting of 30 hermetically sealed 
 cells, simple crank commutator, pole reverser and horizontal galvanometer 
 with pivoted needle, Watteville, Du Bois-Reymond's sliding induction 
 apparatus with adjustable current breaker, in oak box. 
 
 6. A Leclanche Double Apparatus consisting of 40 hermeti- 
 cally sealed cells (Model B), Patent double collector, pole reverser, 
 horizontal galvanometer with pivoted needle, Watteville, Du Bois- 
 Reymond's sliding induction apparatus with adjustable interrupter, in 
 oak box. 
 
 7. A Chromic Acid Battery of 24 cells, Patent double collec- 
 tor, commutator, vertical galvanometer and arrangement for raising and 
 lowering the carbons and zinks; in polished mahogany box. 
 
 8. An induction apparatus on polished wood base. 
 
 9. An induction apparatus on polished walnut base, with switch 
 for 1 or 2 cells. 
 
 10. 2 Induction coils in polished walnut case, 2 dry cells, nickel 
 plated. 
 
 11. 2 Spamer induction coils, simple form in polished mahogany 
 case, nickel plated. 
 
 12. 2 Spamer's Original Induction Coils, nickel plated in maho- 
 gany and walnut case respectively. 
 
 13. i Grenet Induction Apparatus, nickel plated, in polished 
 mahogany case. 
 
 14. i Taube's Induction Apparatus, nickel plated, with inter- 
 changeable secondary coil, in polished case. 
 
 15. i Du Bois-Reymond's Sliding Induction Apparatus, with 
 simple current breaker. 
 
 16. i Du Bois-Reymond's Sliding Induction Apparatus, with 
 Meyer's adjustable current breaker. 
 
 17. i Wimshurst Induction Electrical Machine, with 4 rotating 
 discs of 52 centimeter diameter. 
 
60 Reiniger, Gcbbert & Schall. Erlangen. 
 
 18. Various electrodes for Franklinisation. 
 
 19. i Portable Battery for Galvanic cautery and electric light- 
 ing of 4 cells, crank switch for parallel and series coupling 1 and rheostat. 
 
 20. 1 Portable battery for galvanic cautery and electric lighting of 
 6 cells, commutator and rheostat. 
 
 21. i Portable Accumulator of 4 cells, commutator for 
 cautery and lighting and 2 rheostats. 
 
 22. i Schech's Galvanic Cautery case, small size. 
 
 23. i Schech's Galvanic Cautery case. 
 
 24. 1 Plate showing Galvanic Cautery Instruments. 
 
 25. 1 Electrical Laryngoscope. 
 
 26. 1 Electrical Aluminium Lamp with head band. 
 
 27. 1 Dental Mouth Illuminator. 
 
 28. 1 Electrical Tongue forceps. 
 
 29. 1 Electrical Vaginoscope. 
 
 30. 5 different Conducting Cords for cautery and lighting. 
 
 31. 1 set of Rheophores for galvanisation, faradisation and electrol}*sis. 
 
 32. i Patent Graphite Rheostat in form of an electrode holder. 
 
 33. i Patent Graphite Rheostat in wood frame. 
 
 34. 1 Patent Graphite Rheostat in wood frame with rack and pinion 
 movement for the contact slides. 
 
 35. 2 Patent Graphite Rheostats with 2 ledges. 
 
 36. 1 Patent Graphite Rheostat with 3 ledges. 
 
 37. 1 Crank Rheostat with nickelin wire resistance coils, up to 
 500 ohms, in 60 grades- 
 
 38. 1 Crank Rheostat with nickelin wire resistance coils, up to 
 5000 ohms, 27 grades. 
 
 39. 2 Portable horizontal galvanometers with pivoted needle, reading 
 from 0.1 to 50 milliamperes. 
 
 40. 2 Portable horizontal galvanometers with fibre suspension, 
 reading from 0.1 to 500 milliamperes. 
 
 41. 2 Mueller and Edelmann's Horizontal Galvanometers with 
 fibre suspension and scale reading at a great distance, large and small 
 size, reading from 1 to 500 amperes. 
 
 42. 1 Alternating Current Transformer on switch board for cautery 
 and lighting. 
 
 43. 1 Stationary Switch Board for cautery and lighting, with 
 water cooler. 
 
 44. i Stationary Switch Board for galvanic faradisation, 
 consisting of oak frame, fitted with large Mueller and Edelmann 
 horizontal galvanometer with scale reading at a great distance, 2 crank 
 rheostats for resistances up to 1000 and 5000 ohms respectively in 
 60 grades, graphite rheostat with 4 ledges, pole reverser, Watteville, 
 Du Bois-Reymond's Sliding induction apparatus with adjustable Meyer's 
 interrupter, controlling lamp and 2 instantaneous switches. 
 
Clemens Riefler, Mimchen and Nesselwang. 61 
 
 ]N T 0. 2780. 
 
 Clemens Riefler, Miinchen and Nesselwang. 
 
 (Bavaria.) 
 Manufactory of Mathematical Instruments. 
 
 This firm is exhibiting: 
 
 1. In two show cases: 
 
 Drawing and Measuring Instruments, in particular 
 original drawing instruments (German Patent No. 2907.) 
 
 2. In a third case: 
 
 a.) An absolutely Free Pendulum Escapement with 
 impelling action in the axis of oscillation (German 
 Patent No. 50739). 
 
 b.) A Mercurial Compensation Pendulum (German 
 Patent No. 60059; U. & Patent applied for). 
 
 3. In a fourth case: 
 
 An Astronomical Clock fitted with the escapement 
 and pendulum 2 a. 
 
 I. 
 
 The drawing instruments, which form a speciality of the firm, are 
 of the construction shown in the illustrations and are well known in 
 the technical world as ,,Riefler's Round System Compasses' 4 . The 
 popularity which they have attained is a sufficient proof of their excel- 
 lence of construction and workmanship, which is secured by a number 
 of special machines fitted with the latest improvements. It will be 
 well to here mention that poor imitations of these instruments 
 are placed upon the market; to prevent these being confounded 
 with the Riefler instruments each of the latter has the name of 
 ,, Riefler" stamped upon its head. 
 
 Detailed descriptions of these instruments and specifications of 
 their advantages over the older types written by autorities may be 
 found in the following publications: 
 
 Bayer. Industrie and GewerbeUatt, No. 6, 1886. Dingier' s Poly- 
 techn. Journ. Vol. 241, No. 4. Der prakt. Maschinenconstructeur, No. 328. 
 Wochenschr. des Vereins deutsch. Ingenieure, 1878 No. 22; 1881 No. 16. 
 Leipzig. Illustr. Zeitung No. 1987. ' U Industrie moderne 1889, No. 10. 
 Revue industrial, 1889. Railway Review, vol. XX VIII No. 15. The 
 Tradesman, vol. XIX, No. 4. The Builder and Decorator, vol. Ill 
 No. 1. The Philadelphia Carpet Trade, vol. 6, No. 2. Building, vol.. 
 
<32 
 
 Clemens Riefler, Miinchen and Nesselwang. 
 
 VIII, No. 26: The American Stationer, vol. XXIII, No. 7. The 
 Australasian Ironmonger, vol. XXIII, No. 1. Etc. etc. 
 
 The following may be mentioned among the numerous other drawing 
 instruments exhibited by the firm: 
 
 Riefler's Round System Compasses. 
 
 Beam compasses, reducing compasses, bisector, trisector, harmonic 
 divider, angle trisector, protractors of various sizes, with and without 
 verniers, measures, cross ruling appliances etc. 
 
 II. 
 
 The uniformity of movement of our pendulum chronometers depends 
 mainly upon two conditions, viz. upon the accuracy of the escapement 
 and the completeness of the compensation of the pendulum. 
 
 In both respects Mr. Sigmund Riefler, engineer and partner in 
 the firm, has after many years of experimenting succeeded in constructing 
 pendulums which, according to the practical results recorded at the 
 Munic Royal Observatory and elsewhere, constitute a decided progress 
 in chronometry. 
 
Clemens Riefler. Hiinchen and Nesselwang. 
 
 63 
 
64 
 
 Clemens Riefler, Miinchen and Nessehvang. 
 
 The essentiality of the escapement of this entirely new chrono- 
 metric system, which has also been applied to watches and tower clocks, 
 consists in the manner in which the pendulum, which is absolutely 
 free, is impelled. This is not effected, as is usually the case, by the 
 fork (this is entirely absent), but by the pendulum spring. The 
 latter is, by the action of the wheel work, slightly 
 deflected, the center of t*he deflection coinciding with 
 the axis of oscillation of the pendulum. 
 
 The impulse is, moreover, given nearly at 
 the moment, in which the pendulum passes the 
 position of rest and the supplementary arc of 
 the pendulum is 3 or 4 times as large as the 
 arc of elevation; besides, the number of moving 
 parts is less than with any other escapement. 
 
 The advantages resulting from the whole arran- 
 gement are these: Changes in the magnitude of the 
 transmitted force and the resistance of the pallet action 
 have no practical influence upon the uniformity of the 
 movement, and the chronometer is in a high degree 
 insensible to extraneous disturbances. 
 
 The Mercurial Compensating Pendulum, 
 shown in the annexed figure, has also been devised 
 by Mr. S. Riefler. Its main body consists of a heavy 
 metal disc of such a lenticular form as to freely cut 
 through the air. A Mannesmann steel tube of 16 mm- 
 ? bore and 1 mm thickness constitutes the pendulum rod. 
 | Nearly two thirds of the tube are filled with mercury. 
 ^ In consequence of this distribution of a small quantity 
 e of mercury over a great length, inequalities of the 
 ! temperatures of the upper and lower layers of air and 
 ^ also sudden changes of temperature have only a slight 
 influence upon the pendulum and the movement. 
 
 Unlike all other pendulums, it does not necessi- 
 tate a subsequent correction of compensation, as in 
 this case the latter can be calculated with greatest 
 possible precision. 
 
 Every pendulum made by this firm is, there- 
 fore, warranted to have in no case an error 01 
 Riefler's Mercurial compensation exceeding ^ o,oo5 seconds per 
 
 Compensation-Pendulum. ,. , _i_ n /~ 
 
 diem and per ; i C. 
 
 The principal | advantage of this system, i. e. the escapement in 
 conjunction with thejpendulum, consists in the increased uniformity 'of 
 the movement thereby obtained and in that the latter does no more 
 depend upon fortuitous circumstances but admits of strict computation. 
 
 With the astronomical clocks supplied by the firm the warrant- 
 ed degree of accuracy is i second per week, and with chronometers 
 intended for use as standard clocks for private establishments or for- 
 
Clemens Riefler, Miinchen and Nesselwang. 65 
 
 central regulating- systems the warranted accuracy is 2 seconds 
 per week. 
 
 In the case of Riefler's No. 1 astronomical chronometer fitted up 
 at the Munich observatory the coefficient of compensation of the pendulum 
 for 1 C. is 0,0008 second per diem and the mean error of the movement 
 is 1 second per month. 
 
 Detailed descriptions and recorded results may be had on ap- 
 plication. 
 
 III. 
 
 The firm was established in 1841 and possesses 4 establishments 
 worked by 2 turbines and 2 water wheels of an aggregate power of 
 40 HP. 
 
 The manufacture exceeds per annum 30000 compasses and 60000 
 other instruments. Export extends over all civilized countries. The com- 
 mencement of export to the United States dates 35 years back. 
 
 The firm received first prizes at 10 International and 11 National 
 exhibitions (1892 highest award at Paris, viz. the Diplome d'honneur). 
 
 Agent of the firm in the U. S.: Messrs F. Weber & Co., 
 1125 Chestnut Str., Philadelphia. 
 
66 F. W. Schieck, Berlin. George Schmidt & v. d. Eltz, Schmiedefeld. 
 
 No. 2782. 
 
 P. W. Schieck, Berlin SW. 
 
 14 Halle'sche Strasse. 
 Optical Works. 
 
 Microscope Works, established in 1819 by the father of the- 
 present head of the firm. 
 
 15 Gold and other Medals. 
 
 Exhibits : 
 
 1. New large Microscope with specially large field of 60 to- 
 90 cm apparent diameter; so-called Entomological Microscope. It permits, 
 with magnifications of 300 500, of small insects being viewed in their 
 entirety. 
 
 2. New Revolving Trichinoscope with mechanical stage; with 
 circular object-slides, which may be rotated by means of an endless screw. 
 This microscope has been specially constructed for the examination of meat. 
 
 3. A collection of Student's School and Pocket Microscopes.. 
 
 4. Microscopical Preparations and Accessories. 
 
 No. 2783. 
 
 George Schmidt & v. d. Eltz, Schmiedefeld. 
 
 (Thuringia.) 
 Wholesale Manufacturers 
 
 of Standard Thermometers and Hydrometers. 
 
 All kinds of Chemical and Scientific Glass Instruments and 
 Apparatus. 
 
 Specialities : Thermometers and Hydrometers of all kinds, Graduat- 
 ed Glass Instruments, blow pipe made Glass Apparatus, G-eissler's- 
 Vacuum Tubes, Radiometers etc.; etc. 
 
Franz Schmidt & Haenscli, Berlin S. 67 
 
 No. 2784. 
 
 Pranz Schmidt & Haensch in Berlin S. 
 
 4 Stallschreiberstrasse. 
 Mechanical and Optical Works. 
 
 All the instruments produced by this firm are made under personal 
 supervision by thoroughly trained and skilled workmen. The firm is thus 
 prepared to supply the best and to realize the highest requirements. Be- 
 side the current manufacture of microscopical, polarizing", spectroscopic, 
 photometric and photo-spectroscopic apparatus the firm is engaged in 
 the production of the finest instruments for scientific investigation. 
 Many of the latter have been made for inland and foreign institutes. 
 Among the scientists to whom instruments of this class have been 
 supplied may be named: 
 
 Prof. Cox of Montreal, Prof. Dobrowolski of St. Petersburgh, 
 His Excellency, Prof. v. Helmholtz of Berlin, President of the Impe- 
 rial Physical and Technical Institute, Prof. Hering of Prague, Prof. 
 Holmgren of Upsala, Prof. Arthur Koenig of Berlin, Prof. Kundt of 
 Berlin, Prof. Landolt of Berlin, Prof. V. von Lang of Vienna, Prof. 
 Lippich of Prague, Prof. J. H. Long of Chicago, Prof. Nasini of 
 Padua, Prof. Soret of Geneva, Prof. H. C. Vogel of Potsdam, Prof. 
 H. W. Vogel of Charlottenburg, Prof. Leonhard Weber of Kiel, 
 Prof. Wiley of Washington, Mr. Lewis Wright of London. 
 
 In the following paragraphs a short description will be given of 
 the current apparatus made in this establishment. The greater part of 
 these instruments will be found represented by the exhibits forming part 
 of Group 21 of the Collective Exhibition of the ^Deutsche Gesellschaft 
 fur Mechanik und Optik". Other instruments made by the same firm 
 are shown among the German Educational Exhibits of the Prussian 
 Ministry of Public Instruction. 
 
 A. Spectroscopic Appliances. 
 
 /. Spectrum apparatus with deflected path of rays-, 
 II. Spectrum apparatus with rectilinear path of rays; 
 III. Spectrum apparatus for astronomical purposes; 
 IV. Spectrometers of various types; 
 
 V. Spectrum apparatus for special scientific and technical purposes; 
 VI. Apparatus for demonstrating spectrum phenomena; 
 VII. Auxiliary appliances. 
 
 I. Spectrum Apparatus with deflected path of rays. 
 
 a. Small Spectrum Apparatus. 
 
 Mounted upon a cast iron tripod stand, with column and dish-shaped 
 stage plate fitted with 3 telescopes (viz. observing, slit and scale te- 
 
68 
 
 Franz Schmidt & Haensch. Berlin S. 
 
 lescopes). The slit telescope, which is fitted with a comparison prism, 
 and the scale telescope are fixed upon the stage plate; the observing 
 telescope is made to revolve about its vertical axis. (Fig 1 . 1.) 
 
 Fig. 1. 
 
 b. Medium Size Spectrum Apparatus. 
 
 Mounted upon cast iron tripod stand with brass column and closed 
 prism casing, fitted with 3 telescopes as above. The slit and scale tele- 
 scope are rigidly attached to the prism casing and the observation te- 
 lescope is connected with the latter in such a manner that it may be 
 
 adjusted by rack and pinion coarse and micrometer fine adjustment; any 
 portion of the spectrum may thus be brought into the center of the field. 
 The scale telescope is provided with illuminating flame and the slit 
 telescope is fitted with a comparison prism. The height of the prism is 
 35 mm; the telescope magnifies 10 times. (Fig. 2.) 
 
Franz Schmidt & Haensch, Berlin S. 69 
 
 c. Large Spectrum Apparatus. 
 
 Mounted upon cast iron tripod stand having a conical brass pillar 
 surmounted by a large dish-shaped plate upon which the scale and the 
 scale telescope are rigidly fixed. The observation telescope is made to 
 revolve about the vertical axis of the instrument. The heavy flint glass 
 prism is 45 mm high and is encased in a large black brass hood with de- 
 tachable cover. The telescope magnifies 10 times, or more if desired. 
 
 d. Large Spectrum Apparatus. 
 
 Built after the original of Kirchhoff and Bunsen, mounted upon 
 a large iron tripod having a stout column surmounted by a large iron 
 stage plate, with 4 flint glass prisms of 500 mm height and 4 telescopes 
 (slit, scale, observing and reading telescopes). The objectives of the 
 slit and observing telescopes have a focus of 470 mm and an aperture 
 
 Fig. 3. 
 
 of 45 mm; the magnification of the latter is 40 and 60. To the observ- 
 ing telescope, which is attached to the stage plate, is connected a plane 
 mirror placed below the stage plate, and by means of a separate reading 
 telescope any position of the observing telescope with respect to large 
 wall diagrams may be read off. (Fig. 3.) 
 
 e. Large Spectrum Apparatus with automatic connection of prisms. 
 
 Mounted upon cast iron tripod fitted with levelling screws,- fixed 
 circle and movable alhidada, Rutherford prisms of 4 cm height with 
 automatic connection ; dispersion between A and H 44. The automatic 
 movement is so arranged that 1, 2, 3 or 4 prisms maybe brought into 
 play. 
 
70 
 
 Franz Schmidt & Haensch, Berlin S. 
 
 The two telescopes have objectives of 350 ''mm focus and 43 mm 
 aperture. The magnification of the observing telescope is 30. Divided 
 circle reading to 10 seconds. (Fig. 4.) 
 
Franz Schmidt & Haensch, Berlin S. 
 
 71 
 
 II. Spectrum Apparatus with rectilinear path of rays. 
 
 The adjustments are made in the manner specified under I. Beside 
 the well-known small Browning pocket spectroscope the following types 
 .are made: 
 
 a) Browning's Pocket Spectroscope with 3 prisms, movable 
 slit and reflecting prism for examining two spectra. (Fig. 5 a.) 
 
 b) Spectrum Apparatus according to H. W. Vogel with 
 universal stand. (Fig. 5a, b, c.) The apparatus is fitted in elegant case 
 with all its accessories, such as bottles, bottle holders, mirror, burners etc. 
 and dissectable stand. Eespecting its applicability to many purposes we 
 
 Fig. 5b. 
 
 Fig. 5c. 
 
 refer to the , y Berichte der Deutscli. Chem. Gesellschaft, 1875 and 1876". 
 - If required these instruments are also fitted with scale . 
 
 c) Hoffmann's Spectrum Apparatus. This is made in various 
 sizes, also in pocket form. The apparatus shown in the German Edu- 
 cational Exhibition is fitted with scale and comparison prism. The 
 Jan sen body consists of two parts whose relative position is adjustable. 
 The Fraunhofer lines remain in all positions at minimum deviation. 
 
72 
 
 Franz Schmidt & Haensch, Berlin S. 
 
 III. Spectrum Apparatus for Astronomical Purposes. 
 
 a) Zoellner's Astro -Spectro graph with 2 cylindrical lenses. 
 Dispersion between D and Or : 3. 
 
 b) H. C. Vogel's rectilinear path Astro - Spectrograph. 
 (Fig. 6 a und 6b.) 
 
 Fig. 6 a. 
 
 Fig. 8. 
 
 c) H. C. Vogel's Deflected path Astro-Spectrograph. 2 prisms 
 with scale. (Fig. 7.) 
 
 d) Spectro -Photometer own construction, according to sug- 
 gestions of H. C. Vogel. 
 
 e) H. W. Vogel's Small Spectrograph. (Fig. 8.) 
 
Franz Schmidt & Haensch, Berlin S. 75 
 
 f) H. W. Vogel's Large Spectrograph mounted upon a 
 
 Fig. 9. 
 
 standard, with 2 Kutherford prisms of 45 mm height and bilateral slit; 
 prisms and telescope automatically connected. (Fig. 9.) 
 
 IT. Spectrometers according to Victor von Lang. 
 
 These instruments are mounted upon a tripod stand fitted with 
 elevation screws. The tripod supports a gun metal pillar into the bore 
 of which fits a steel center to which is attached the steel circle. 
 
 a) Small size. Magnification of telescopes 8. The collimator is 
 fitted w j ith micrometer slit and reflecting prism. The positive ocular of 
 the observing telescope may be replaced by a Gauss ocular. The circle 
 is divided in l / 2 degrees and reads by two verniers to minutes. 
 
 b) Medium size. Magnification of telescopes 10. Telescope and 
 collimator. tube in fixed adjustable bearings. The diameter of the divided 
 circle is 170 mm. It is divided in 1 / 3 degrees on German silver, reading 
 to 30 seconds by the two verniers. 
 
74 
 
 Franz Schmidt & Haensch. Berlin S. 
 
 c) Large size. Magnification of the telescopes 10 or more. Slit 
 with reflecting prism. The circle of 170 mm diameter is divided in l / Q 
 degrees on silver, reads to 10 seconds and is protected from dust by a 
 brass hood. 
 
 These sizes are, on account of their stability, specially adapted for 
 automatic connections with several prisms, also for equipment with polar- 
 izing apparatus and Babinet's compensator, crystal movement and so 
 forth. The usual collimator may be easily replaced by Kundt's collimator, 
 which is specially adapted for photometric purposes; the latter is fitted 
 with micrometer screw and bilateral slit with helioscopic objective. The 
 latter can be gradually closed by segments. 
 
 T. Spectrum Apparatus, for special scientific and technical 
 
 purposes. 
 
 a) Spectrum-Photometer according to von Vierordt for photo- 
 metry or qualitative and quantitative chemical spectrum analysis, with 2 
 telescopes; the observing telescope is fitted with rack and pinion and 
 ocular slit, the collimator tube with double slit, divided drum and reflecting 
 prism. Large and small model. 
 
 b) Spectrum-Photometer according to Glan with reversion of 
 the Nicol prism. 
 
 H 
 
 Fig. 10. 
 
 vid. 
 
 One of the most popular apparatus. (Fig. 10.) (For particulars 
 Poggendorfs Ann., 1877. - - Vogel, ,,Das Spektroskop."} 
 
 c) Spectrum-Photometer according to A. Koenig. 
 
 d) Ophthalmo-Spectroscope, simple and composite, for testing 
 colour blindness, according to vonVierordt's andHolmgren's suggestions. 
 
Franz Schmidt & Haensch, Berlin S. 
 
 75 
 
 e) Spectro-Photometer made according to Lu miner and Brod- 
 hun for the Imperial Physical and Technical Institute. 
 
 Fig. 11. 
 
 The apparatus is fitted with 2 collimators placed at right angles 
 to one another, provided with bilateral slits and micrometer screws. The 
 
 observing telescope 
 S fiK lias an ocular slit. 
 
 . J .i^.Ji^aBBL 
 
 The apparatus is 
 
 sufficiently sensi- 
 tive for the most 
 
 exacting require- 
 ments. Further par- 
 ticulars may be ob- 
 tained from the re- 
 presentative of the 
 firm at the Exhi- 
 bition. (Fig. 11.) 
 
 Fig. !_>. 
 
 f) Helmholtz's Colour Mixing Apparatus, for mixing 2 to 4 
 different spectra of any intensity, with Rochon's prisms and bilateral 
 slits (vid. PL v. Helmholtz, ,,Handbuch cler Physiologischen Optik.") 
 
76 
 
 Franz Schmidt & Haensch, Berlin S. 
 
 g) Helmholtz's Large Colour Mixing Apparatus with Lummer 
 and Brodhun's prism combination, 5 telescopes, 4 collimators with 
 bilateral slits and Rochon's prisms, polarizing arrangements before the 
 
 slits and the observing telescope 
 with ocular slit. The apparatus 
 is shown in the German Edu- 
 cationa I Exhibition . 
 
 h) v. Prey's and v. 
 Kries's Spectrum Apparatus 
 for mixing spectrum colours (vid 
 Report of the Physiological In- 
 stitute, in Leipzic). 
 
 i) Colour Mixing Appa- 
 ratus, own construction, with 
 D on ders's bilateral slit. (Fig.l 3.) 
 
 YI. Apparatus 
 
 for demonstrating 
 
 Spectrum Phenomena. 
 
 (Among ,, Apparatus for ob- 
 jective demonstration"). 
 
 YII. Auxiliary Appliances. 
 
 There are a large number 
 of these but only the following- 
 few are of special interest: 
 
 a) Steinheil's Hollow 
 Prisms with piano -parallel 
 sides. 
 
 b) Wernicke's Hollow 
 Prisms, consisting of 2 crown 
 glass wedges cemented into a 
 glass box, the interspace be- 
 tween the wedges being filled 
 with cinnamomic ethylic aether. 
 The prism is protected from the 
 influence of variations of tempe- 
 rature by a wood casing. The 
 prism is remarkably transparent 
 and possesses great dispersion. 
 It is adapted both for the de- 
 flected and the rectilinear path 
 of rays. 
 
 c) Set of Jansen's and Amici's Prisms; 3 or 4 prims. 
 
 d) Eutherford Prisms, consisting of a flint glass and two crown 
 glass wedges; specially recommended for high dispersions. 
 
Franz Schmidt & Haensch. Berlin S. 
 
 77 
 
 e) Reflecting Prisms of various sizes. 
 
 f) Heliostats of various types. (Fig. 14, according to Spencer.) 
 
 Fig. 14. 
 
 g) Spectrum tubes and tables etc. 
 
 B. Photometric Appliances. 
 
 The increased requirements of stronger and better artificial illumi- 
 nation have created a demand for accurate appliances for measuring the 
 power and quality of illuminants. 
 
 The following appliances constructed by this firm have met with 
 particular favour: 
 
 I. Leonhard Weber's Photometer. 
 
 The instrument is adapted not only for determining the intensity 
 of flames or similar illuminants but also that of diffuse light. (Fig. 15.) 
 
 The apparatus with its accessories is neatly fitted in an elegant 
 case with handle; it is conveniently portable and therefore specially 
 available for measurements of any kind, in cases where other photometers 
 
78 
 
 Franz Schmidt & Haensch, Berlin S. 
 
 cannot or can only with great inconvenience be used. The instrument is 
 indispensable for examining the light admitted into school rooms etc. 
 
 Fig. 15. 
 
 Detailed description and directions for use may be had of the" 
 firm's representative. 
 
 II. L. Weber's Apparatus for measuring solid angles (Fig. 16). 
 
 ,P 
 
 Fig. 16. 
 
 For measuring the solid angle contained by the incident rays and 
 the illuminated surface. (For further particulars vid. Description alluded 
 to above.) 
 
Franz Schmidt & Haenscli, Berlin S. 79 
 
 III. L. Weber's Photometer with Polarizing Apparatus. 
 
 The instrument is particularly adapted for measuring 1 the brightness 
 of the sky, the c\ouds, the relative distribution of the brightness of the- 
 sky etc. 
 
 IV. Photometer Bench. 
 
 It consists of a cast iron frame with 5 elevation screws, 2 rails of drawn 
 steel tubing, one of which is throughout divided in millimeters, the other 
 according to standard candle units. 3 waggons provided with pointers run upon 
 these rails and are fitted with rack and pinion movement and clamping screws- 
 for accurately adjusting the height of the various luminants. The bed is made- 
 of any required length. As a rule the available length is 250 cm. A completely 
 equipped specimen 150 cm in length is shown at the Exhibition. 
 
 For this photometer bed 2 heads are supplied constructed according 
 to Lummer's and Brodhuri's directions, viz. 
 
 a. Photometer head for equalized luminosities, 
 
 b. Photometer head for equalized and contrasted light, (fig. 17)1 
 
 Fig. 17. 
 
 Vid. >> Photometric Researches-' by Dr. Lummer and Brodhun in the- 
 Zeitschrift fur Instrument enkunde, 1892 and in Schilling, Journal fur 
 Gasbeleuchtung und Wasserversorgung, 1892, No. 29. 
 
 These appliances, which were originally constructed at the insti- 
 gation of the Imperial Physical and, Technical Institution, are already 
 being largely used by prominent gas and electric light works. 
 
Franz Schmidt & Haensch, Berlin S. 
 
 C. Appliances for Objective Demonstration. 
 
 The great practical value of objective demonstration becomes more 
 and more acknowledged and, accordingly, this method of instruction is 
 being adopted by an ever increasing circle of colleges and schools. 
 According to the available means and the source of light, apparatus for 
 various forms of illumination and of varying sizes are in requisition, viz. 
 for lamp, zirconium (coal-gas and oxygen) and electric light. 
 
 I. Appliances for electric light 
 
 of various sizes with double or triple illuminating system and with lenses 
 of 105 to 300 mm diameter according to the size of the object which 
 is to be shown on the screen. The apparatus is fitted with water tank. 
 The contact lamp of von Hefner-Altenek, adjusted for 15, 20 or 
 25 Amperes forms a suitable source of light. 
 
 a. Large Camera lor Elec- 
 tric light, 
 
 own design, made of brass. Per- 
 fectly light-tight casing. The side 
 doors are balanced by counter 
 weights and are made to move 
 upwards. Diameter of the two 
 illuminating lenses 105 mm. The 
 whole lamp can by means of a 
 rack and pinion movement be 
 raised and lowered, and by means 
 of a lateral sliding arrangement 
 the source of illumination can 
 always be brought into the opti- 
 cal axis. 
 
 b. Large Mahogany Camera, 
 lined with asbestos inside; equip- 
 ment otherwise similar to that of a. 
 
 c. Large Camera, 
 own design, of brass fitted with 
 all the above mentioned improve- 
 ments. The carbons are contained in a casing which is accessible by 
 three doors, the lower portion of the lamp being open for manipulation. 
 (Fig. 18.) 
 
 Fig. 18. 
 
Schmidt & Haensch, Berlin S. 
 
 SI 
 
 d) Large camera, own design. 
 
 The two illuminating lenses of 235 mm diameter may be placed 
 in different relative positions by means of wheels running upon steel 
 tubes. They are connected with one another and with the camera by 
 
 8- 
 
 Fig. 19. 
 Linnemann burner, vide pag. 82. 
 
82 Schmidt & Haensch, Berlin S. 
 
 bellows. Either lens can be quickly removed, it being thus possible 
 to work with a single lens, which greatly facilitates many experiments. 
 
 e) Camera with encased Schuckert lamp, with slanting car- 
 bons, to obtain the best illuminating effect; the carbons ma}* also be 
 placed vertically for spectrum analytical experiments. 
 
 II. Projection Apparatus for Zirconium Light. 
 
 The zirconium lamp invented by Prof. Linnemann, which is 
 worked by a coal-gas and oxygen burner, emits a light of about 
 200 caudles and is the best substitute for electrical light in cases 
 where the latter is not available. It is mounted upon large and small 
 stands. (Fig. 19 pag. 81.) 
 
 a) Large camera with large Linnemann burner, with two 
 illuminating lenses of 105 mm diameter, all brass lackered black, with 
 nickel mountings. 
 
 b) Small camera with small Linnemann burner, of tin plate, 
 with two lenses of 105 mm diameter, mounted upon mahogany base. 
 
 Fig. 20. 
 
 If required these apparatus are also supplied with larger lenses and 
 various equipments. (Fig. 20.) 
 
 c) Enlarging camera, with two lenses of 155 mm diameter 
 for photographs not exceeding 9X12 cm: mounted on mahogany board, 
 with movable objective bellows, arrangement for moving the illuminat-, 
 ing lenses, iron casing for the burners. 
 
 d) Mahogany Enlarging Camera, with two illuminating lenses 
 
Schmidt & Haensch, Berlin S. 
 
 83 
 
 of 235 mm diameter for photographs not exceeding 13 X 18 cm. (Fig. 21.) 
 This and camera c are specially adapted for photography. 
 
 Fig. 21. 
 
 III. Optical Benches for demonstrating polarization and spectrum 
 phenomena and for microscopical projection on the screen. 
 
 a) Large optical bench. 
 
 It consists of an iron bench fixed upon a mahogany base board 
 provided with 6 sliding blocks which may easily be moved along the 
 bench and clamped in any position. 
 
 The standards for various appliances attached to these sliding 
 blocks are fitted with rack and pinion for adjusting the heights. 
 
 The equipment is, of course, adapted for the optical departments 
 which are to be demonstrated. For polarization with parallel and con- 
 vergent light two large Nicol prisms, black mirrors, sets of glasses, 
 glass clamps etc. are supplied with the bench. For spectroscopy a 
 slit arrangement, collimator lens, prisms placed upon a stage etc. 
 accompany the bench. A complete optical bench provided ivith the Schuckert 
 camera le is shown at the exhibition. 
 
 b) Small optical bench, consisting of two stout nickel plated 
 brass tubes mounted upon mahogany base board, provided with 6 or 
 7 sliding pieces with draw tubes for adjusting the height. 
 
84: 
 
 Schmidt & Haensch, Berlin S. 
 
 . Equipment similar to that of a (Fig. 22). This bench is shown at. 
 the German Exhibition. 
 
 o 
 
 Fig. 22. 
 
 c) Optical bench specially designed for microscopic pro- 
 jection. It consists of a short bench mounted upon wood base with 
 two slide blocks, one of which is fitted with stage for absorption, 
 vessels (light filters) etc., the other forming a suitable support for a 
 complete microscope. 
 
 Fig. 23. 
 
 The latter consists of a rotating mechanical stage, a condenser 
 fitted with rack and pinion movement and a sleeve for objective tubes 
 adjustable by a micrometer screw. 
 
Schmidt & Haensch, Berlin S. 85 
 
 The sleeve is adapted both for a short tube intended to take 
 low power lenses and for a long tube fitted with worm screw intended 
 for higher powers, apochromatic lenses in conjunction with projection 
 oculars. (Fig. 23.) 
 
 d) Projection head, for projecting photographs and objects in 
 general by means of photographic lenses. The focus of these lenses 
 must, of course, be adapted to the focus of the illuminating lens of 
 the Camera. We must here refer to the Separate Catalogue on ^Optical 
 Benches'', n-h'n-h may be had from tlte firm's representative. 
 
 D. Polarizing Appliances. 
 
 Beside the well knowD instruments of Mitscherlich, Laurent, Wild, 
 Xandolt-Lippich, Soleil-Yentzke's colour apparatus and Jelett-Cornu's pen- 
 umbra apparatus, the firm makes also new appliances for observing electric 
 and magnetic rotation, for polari-spectro- photometric research etc. These in- 
 struments are all of the most approved form and perfect workmanship, both 
 as regards the optical and mechanical parts. 
 
 I. Appliances for didactic purposes. 
 
 a) Dove's apparatus for demonstrating polarization pheno- 
 mena, consisting of a divided prismatic beam with sliding pieces 
 provided with brass standards for the accessories, with open telescope 
 fitted with divided circle, with Nicols, condensers etc. 
 
 b) Noerremberg's Apparatus with accessories. 
 
 c) Wild's, Laurent's apparatus and others, vid. II. 
 
 d) Arago's, Babinet's, Savart's, Senarmont's polariscopes. 
 (vid. also under heading ,, Optical benches' 4 .) 
 
 II. Apparatus for analytical purposes, for homogeneous light, 
 with divided circular disc. 
 
 a) Mitscherlich's apparatus; simplest form with two Nicols, 
 1 lens and 1 observation tube 200 mm long," on stand. 
 
 b) Robiquet's apparatus.; equipment similar to that of a, but 
 with the addition of a double rock crystal plate. 
 
 c) Wild's apparatus, large model, on adjustable brass stand, 
 with interposed Savart plate, with circle divided on silver, telescopic 
 reading, with observation tubes of 220, 200 and 100 mm length and 
 with sodium gas lamp ; the whole apparatus fitted in a mahogany box. 
 
 d) Wild's apparatus, small model, with observation tube of 
 100 mm length. 
 
 (These Wild instruments are very sensitive, but are not suitable for long 
 continued working owing to the eye being severely strained by their use.) 
 
86 Schmidt & Haensch, Berlin S. 
 
 e) Mitscherlich's Penumbra Apparatus, original construction, 
 
 Fig. 24. 
 
 with Laurent polarizer. With two observation tubes and sodium 
 gas lamp. 
 
 (Eminently suitable for analysis of wine, must etc., Fig. 24.) 
 
 Fig. 25. 
 
 f) Laurent's Penumbra Apparatus, with Laurent polarizer, 
 consisting of a single Nicol and a rock crystal plate, with observing 
 tubes of 220, 200 and 100 mm length and with sodium gas lamp. 
 
 (This apparatus is particularly adapted for exact chemical analysis; read- 
 ing to 1 minute, Fig. 25.) 
 
Schmidt & Haensch, Berlin S. 
 
 87 
 
 g) Landolt's Apparatus with Lippich's polarizer. Three 
 modalities. 
 
 The optical equipment is with all three the same. The instruments differ 
 only in the fineness of the divisions on the circles and the necessary means for 
 taking the readings. The first two instruments are intended for determining 
 the rotating powers of fluids, the third instrument can, at the same time, be 
 used for examining electro-magnetic rotation. The instruments consist of two 
 stout brass or iron standards, which are rigidly connected by stout brass rods. 
 Upon these rests a sliding block which may be easily moved horizontally by 
 means of a lever. The sliding block supports the observation tubes. The rigi- 
 dity of the mechanical fittings and the, arrangement of the optical part render 
 the apparatus extremely sensitive. The Laurent polarizer is replaced by a 
 Lippich polarizer. The latter consists of a fixed Glan Nicol which occupies 
 the entire field arid a movable Nicol which fills only one half of the field. By 
 rotation of this latter Nicol the brightness of the penumbra may be regulated. 
 While with Laurent's system only sodium light is applicable the Landolt- 
 Lippich instrument possesses the advantage of admitting of any kind of homo- 
 geneous light being used, 
 
 1. Landolt-Lippich Apparatus with observation tubes of 100, 
 200, 800 and 400 mm length, with large silvered circle divided in 
 1/5 degrees, reading by verniers and simple magnifiers to 0.01 degree. 
 With Landolt lamp for homogeneous light. (Fig. 20.) 
 
 2. Landolt-Lippich Apparatus with observation tubes of 600, 
 500, 400, 300, 200 and 100 mm length. The circle is divided on 
 silver in 400 parts and reads by two microscopes to 0.001 degree. 
 Accessories: Landolt's lamp for homogeneous light and 2 lamps, each 
 with 2 glass rods, for illuminating the divided circle and the micro- 
 scope drums. 
 
88 
 
 Schmidt & Haensch, Berlin S. 
 
 3. Landolt-Lippich Apparatus for observing electro-magnetic 
 rotation, with bobbin running on wheels, copper wire solenoid into 
 which is inserted the observation tube. The bobbin runs upon two 
 brass rails and may readily be brought into the optical field. A sup- 
 port for ordinary observation tubes not exceeding 600 mm in length 
 is supplied with the apparatus to render it available for the examination 
 of liquids. Accessories: as under 2. 
 
 III. Apparatus for white or lamp light with wedge 
 compensation and linear scale. 
 
 Equally exact and convenient, but adapted for substances which, like 
 cane sugar, have the same dispersive power as rock crystal; therefore chiefly 
 patronized by sugar refineries and by the custom house, 
 
 a) 1. Soleil-Ventzke's Colour Apparatus 
 
 Fig. 27. 
 
 with adjustment for certain colours in either half of the field, with 
 observation tube of 200 mm and another of 100 mm length, in maho- 
 gany case. (Fig. 27.) 
 
 2. The same apparatus, with tubes of 400, 200 and 
 ICO mm length. 
 
 3. The same apparatus with tubes of 600, 400, 200 and 
 100 mm length. 
 
 b) The same apparatus with double wedge compensation. 
 Original design. 
 
 1. for tubes of 200 mm length, 
 2/ 400 
 3. 600 
 
 (The double wedge compensation with 2 movable rock crystal wedges 
 and scales belonging thereto admits not only of polarization to the left from 
 to 100, but also of easy control of both scales along their entire length, 
 in 1/10%). 
 
Schmidt & Haensch, Berlin S. 
 
 89 
 
 c) 1. Penumbra Apparatus, with adjustment for equal bright- 
 ness of the two halves of the field; for tubes of 200 mm length. 
 X 
 
 Fig. 28. 
 
 2. for tubes of 400 mm length, 
 
 3. 000 .. 
 
 Equipment and accessories similar to those of a. (Fig. 28.) 
 
 d) The same apparatus with double], wedge compensation. 
 Original design. 
 
 n 
 
 Fig. 29. 
 
 1. for tubes of 200 mm length, 
 
 2- 400 
 
 3. 600 
 Equipment and accessories similar to those of a. (Fig. 29.) 
 
 Adjustment for equal colouring of the field is impossible in cases of 
 colour blindness and it is inexact where the capacity for discerning colours is 
 imperfect; besides, it is, with continued working, for the majority of eyes much 
 more straining than the adjustment for equal brightness. For this reason 
 the majority of analysts obtain more exact results with the penumbra 
 
90 Schmidt & Haensch, Berlin S. 
 
 apparatus than with the corresponding colour apparatus, and the pen- 
 umbra apparatus is, therefore, more and more taking the place of the 
 colour apparatus. 
 
 c) 1. Stammer's apparatus for testing beet root. It has 
 the same optical construction as the penumbra apparatus c. Its scale 
 is, however, limited to a range from to 85. AVith two observation 
 tubes of 200 mm length. 
 
 2. The same apparatus for tubes of 400 mm length, with 
 2 tubes 400 mm long, in case. 
 
 f) Apparatus, original construction, 
 
 Fig. 30. 
 
 similar to e, for urine sugar and albumen tests, reading to 
 0,1%, with one observation tube of 200, 100 and 50 mm respectively. 
 In mahogany case. (Fig. 30.) 
 
 The instruments enumerated under a, b, c and d are now only fitted 
 with nickelin scales, and a reflecting illuminator is recommended for convenient 
 reading. 
 
Schmidt & Haensch, Berlin S. 01 
 
 IV. Accessory Appliances for Saccharometers. 
 
 The following few appliances may here be quoted from the extensive list 
 contained in the special catalogue of these appliances made by 'this firm. 
 
 a) Observation lamp for petroleum (Rinks' duplex burner) 
 with metal chimney, with illuminating lens and reflector. 
 
 b) Observation lamp for gas, original construction (triplex 
 burner) with metal chimney, with illuminating lens arid reflector. 
 
 c) Observation lamp for electrical light. 
 
 dj Observation lamp for sodium light (for gas) for polari-strobo- 
 meters and circular penumbra instruments. 
 
 e) Observation tubes with and without water jacket, Pellet's 
 observation tubes for continuous filling, controlling observation tubes 
 for testing the apparatus with simple wedge compensation. 
 
 f) Standard quartz plates for testing the apparatus with 
 simple wedge compensation. 
 
 g) Balances, chemical, for analysis and technical purposes and 
 specific gravity balances; various systems and equipments. 
 
 h) Apparatus for determining the percentage of carbonate 
 of lime in bone charcoal. 
 
 i) Apparatus for Volumetric determination of the carbonic 
 acid contained in saturation gases, according to Scheibler, Kohl- 
 rausch and others. 
 
 k) Ventzke's Hydrometer. 
 
 1) Brix's Standard Saccharometer (Hydrometer), 
 m) Beakers, Burettes, Pipettes etc. 
 n) Complete laboratory outfits. 
 
 o) Complete travelling equipments. 
 
 E. Microscopy. 
 
 Beside various forms of reading and cathetometric microscopes, 
 scale telescopes and other dioptric appliances for the above compound 
 instruments, this firm supplies a varied assortment of microscopes for 
 all usual magnifications. See separate catalogue. 
 
 Sole agents for the U. S. A.: 
 
 Messrs. Eimer & Amend 
 205-211 Third Avenue New York. 
 
92 G. A. Schultze, Berlin S.O. 
 
 No. 2787. 
 
 G. A. Schultze, Berlin S.O. 
 
 Koepenickerstrasse 128. 
 Glas- Blowing and Mechanical Works. 
 
 Established 1850. 
 Proprietor: Paul Schultze. 
 
 Awards: 
 Paris 1855, Gold Medal of the Academic Nationale. 
 
 Paris 1892, Gold Medal. 
 
 Munic 1854. -- Paris 1855, Exposition Internationale. -- Stettin 1865. 
 Porto 1865, Diploma of honour. - - Philadelphia 1876. 
 
 The firm is engaged in the manufacture of accurate glass instru- 
 ments of all kinds, for scientific, commercial and official pur- 
 poses, such as 
 
 Standardized Thermo-alcoholometers. 
 
 -hydrometers. 
 
 Standard Thermometers, Standard Saccharometers; 
 Measuring Appliances for laboratories etc. etc. 
 
 A speciality of the firm consists in their thermometers for all 
 kinds of purposes, of which a large^ assortment is being exhibited. 
 In the manufacture of this class of thermometers, special weight is 
 attached to greatest possible distinctness and durability. In order 
 that these two conditions may be satisfied a departure w r as made from 
 the usual form of sealed thermometers consisting of sealed capillary tube 
 and scale encased in the outer tube, and the scale of the new thermometer 
 w r as made in the shape of a box. This construction admits of the 
 dimensions of the scale being made much larger than is possible 
 w r ith the usual type. This again renders it possible to use much thicker 
 capillary tubes of prismatic section. A thick column of mercury is 
 used and this again appears magnified several times by the action of 
 the glass. These broad ribbons of mercury, which are visible from a 
 distance, in conjunction with the deep divisions and large figures, impart 
 to these instruments a distinctness which has not been attained elsewhere. 
 The exhibits will bear out this assertion. This mode of construction has 
 the further advantage of admitting of a much more solid form of 
 
G. A. Schultze, Berlin S.O. 93 
 
 framing, which may be made of cast iron or yellow metal and thus 
 ensures great durability. The mercury bulbs of these thermometers are 
 protected from bursting by the following device, which has been adopted 
 almost exclusively in all these thermometers. It consists in the bulb of 
 the capillary tube being protected by a closed iron tube which terminates 
 in the connecting flange or nut. The source of heat (steam, boiling water 
 etc.) is thus prevented from touching the glass bulb directly. The iron 
 tube is filled with mercury which completely surrounds the bulb, thus 
 communicating to the latter the external temperature with such rapidity 
 that the indications of such a thermometer are quite as rapid as those 
 of a thermometer with uncovered bulb. This arrangement has proved 
 to be the most perfect protectbr of the mercury bulb, and on this 
 account the town council of the City of Berlin employ these 
 thermometers exclusively. 
 
 The special advantages of these thermometers have quickly gained 
 a large market for them. The firm counts among its regular customers, 
 beside the town council of Berlin, numerous municipal autorities 
 and important establishments, as may be seen from the references of 
 gas works, breweries, distilleries, sugar refineries, chemical 
 works etc. 
 
 The firm has acquired the sole right of manufacture within 
 Germany of patent No. 59861, Schmidt's self-acting steam throttling 
 apparatus and No. 40295, Moennich's distance thermometer, 
 and besides possesses an original patent for an apparatus for auto- 
 matic registration of the specific gravity of liquids, which is par- 
 ticularly valuable for the purposes of sugar works. 
 
 In 1888 and 1889 the firm received from the Imperial Assize 
 Commission an extensive order for the supply of Standard Thermo - 
 alcoholometers for the German Customs. 
 
94 
 
 Schulze & Bartels, Ratbenow. 
 
 Xo. 2788. 
 
 Sckulze & Bartels, Rathenow. 
 
 Sole proprieter: Franz Bartels. 
 Optical Works. 
 
 Established in 1850. 
 
 I. Department: Spectacle Glasses made of glass and pebble. 
 Cylindrical glasses, illuminating lenses, plano-convex and biconvex lenses 
 for all purposes. Spectacle frames, folding spectacles, ophthalmic appli- 
 ances, optometers. 
 
 Fig. 1. Photograph taken with the older type of lens. 
 
 II. Department: a. Telescopes for tourists, military reconnaissance 
 and navigation. Exemplified at the Exhibition 1.) by a conical marine 
 telescope as supplied to the German Navy, with object glass of 62 mm 
 diameter, extremely large field and 2.) by a reconnoitring telescope 
 of 36 mm aperture for the artillery. 
 
 b) Telescope Objectives made in the most exact manner, 
 in particular for measuring-telescopes. Various types according to parti- 
 cular purposes. Optical or chemical chromatic correction. Compensation 
 of spherical aberration in either direction for cathetometers. Very short 
 
Schulzo & Bartels, Rathenow. 
 
 95 
 
 focal lengths with relatively large apertures. Exemplified at the Ex- 
 hibition by a set of telescopic objectives of diameters up to 108 mm. 
 
 c) Photographic Objectives. Aplanatic lenses, lenses for detect- 
 ive cameras, cheap photographic objectives for amateur apparatus. 
 
 d) Tele-objectives according to Dr. Miethe for direct photo- 
 graphy of very distant objects. Exemplified at the Exhibition by a 
 specimen having an aperture of 40 mm. (Fig. 1 u. 2.) 
 
 Fig. 2. Photograph taken with Dr. Miethe's tele-ohjective. 
 
 (Showing the part marked in Fig. I taken from the same position.) 
 
 d) Hemispheres for microscopes, polarization apparatus etc. Exem- 
 plified by a set of various sized hemispheres. 
 
 f) Binoculars of a special optical type, for military and marine 
 purposes. Exemplified at the Exhibition by several ^binoculars as sup- 
 plied to the German infantry, artillery and navy. 
 
96 Schott & Genossen, Jena. 
 
 No. 2786, 
 
 Schott & Genossen, Jena. 
 
 Olasteclmisches Laboratorinm. (Glass Works.) 
 
 Optical Glasses and Glass-tubing for Thermometers etc. 
 
 The Glass Works of Schott & Genossen in Jena were founded 
 in 1884 .and had their -origin in a laboratory for scientific experiments 
 in glass smelting. The first investigations made in 1883 and 1884 by 
 Dr. Otto Schott in conjunction with Prof. Abbe, and later experiments 
 on a manufacturing scale, in which they were liberally supported 
 financially by the Prussian Government, resulted in the production of a 
 series of glasses beside the ordinary Crown and Flint glasses of the new 
 Baryta, Phosphate and Borate series, which led the way to the con- 
 struction of improved optical instruments. We may mention among 
 these: Improved microscope objectives of the ordinary (achromatic) series,. 
 Apochromatic microscope objectives and apochromatic photographic 
 lenses, Improved Aplanatic lenses (envolving the use of Baryta glasses), 
 the Anastigmatic lenses recently constructed by Carl Zeiss and 
 Telescopes with diminished secondary spectrum. 
 
 The application of a very accurate process of annealing enables the 
 glass-works to produce pressed lenses and large objective discs free 
 from internal strain. 
 
 The Laboratory produces also special glasses for scientific and 
 technical purposes: 
 
 Tubes of the ,,Jena Standard Glass" (registered trade-mark: 
 One red line) with diminished secondary thermal effect and minimised 
 variability of the zero-point, for fine and accurate thermometers. Glasses 
 of a very high and also very low coefficient of expansion. Combustion 
 tubes and tubes for Explosion furnaces. Compound tubes for Water- 
 gauges, consisting of two glass layers of different expansive powers 
 fused together, capable of resisting, in a high degree, sudden changes 
 of temperature and the corrosive action of water. 
 
 The Laboratory is prepared to compound and smelt such special 
 glasses which are calculated to lead to improvements. 
 
 Exhibits : Discs for Telescope Objectives, polished slabs of Optical 
 Glasses (ordinary Crown glasses, heavy and heaviest Baryta -Crown 
 of high refractive power, Crown glass of high and low dispersion, Phosphate 
 and Borate glasses free from silica, Baryta light flints, ordinary Flint 
 glasses with refractive powers up to 1.9), moulded and annealed lenses 
 for the Zeiss Anastigmatic and other photographic lenses; Prisms for 
 total reflection. - - Jena standard glass-tubes, Borosilicate glasstubes, 
 Combustion-tubes, Tubes for Explosion furnaces and Compound Tubes. 
 
Dr. Steeg & Reuter, Homburg. 
 
 <J7 
 
 No. 2790. 
 
 Dr. Steeg & Reuter, Homburg vor der Hohe. 
 
 (Bath Homburg.) 
 Optical Institute. 
 
 Established in 1855. 
 
 Diploma of Honour: 
 
 tiraz 1880. 
 Frankfort a. M. 1881. 
 
 Gold medal: 
 Antwerpen 1885. 
 
 WITAUSSTELIUNG 1873 MEN 
 DEM FORTSCHRITTE* 
 
 Diploma 
 of Honour 
 
 Bruxelles 
 
 1888. 
 
 Gold medal at the I. International Pharmaceutical Exhibition, 
 in Vienna, 1883. 
 
 Short description of exhibited objects: 
 
 No err emb erg's Polarizing Apparatus with large field and gonio- 
 meter for measuring the inclination of axes. 
 
 Nodot's polarization apparatus, also suitable for projection. 
 
 Polarimeter or Saccharometer for quantitative analysis for all kinds 
 of sugar and quinic alcaloids. 
 
 Turmalin forceps with and without lens. 
 
 A collection of 261 cleft crystals, uni- and biaxial, for experiments 
 on dichroism etc.; and No err emb erg's mica films, in mahogany case. 
 
 7 
 
98 Dr. Steeg & Reuter, Homburg. 
 
 Calcite Preparations: Nicol's Prisms, amongst these one of 
 abnormal size, an unique specimen, 40 mm (1 2 /V) across the face; various 
 polarizing prisms a la Foucoult, Grlan, Hartnack, Jellet-Cornu; double 
 refracting prism. 
 
 Three large rhomboeders with various surfaces. 
 
 Quartz Preparations: Large prisms and lenses on brass stands. 
 
 A tube of nickel-plated brass with quartz lenses for spectroscopic 
 examinations with Soret's movable ocular and uranium glass disc, double 
 refracting prism and tube for liquids. Babinet's compensator in brass mount. 
 
 Quartz wedges, double disc, Bertrand's quadruple plate, double 
 refracting prisms and Fresnel's triple prism; a large sphere. 
 
 Selenite Preparations: Various wedges, concave discs, various 
 Selenite figures. 
 
 A collection of 16 unannealed glasses, in case. 
 
 Interference Apparatus: Fresnel's Mirror Apparatus, on brass stand. 
 Interference prism, Billet's lens, cylindrical lens, all on brass stands. 
 Newton's coloured rings, in brass mount. 
 
 Fluorescence: Four cubes of uranium -didym-saphirin glass and 
 fluor-spar, in case. 
 
 Perforated case with 5 fluorescent liquids. 
 
C. Staudinger & Co., Giessen. 99 
 
 IS T o. 2791. 
 
 C. Staudinger & Co., Giessen. 
 
 Philosophical Instrument Works. 
 
 A. Department for Precision Balances and Weights. 
 
 I. Rapidly oscillating universal Precision Balance; is sub- 
 -stancially a high precision balance, for the determination of weights up 
 to 500 grammes (resp. 1000 grammes) which, as such, comes fully up to 
 modern requirements, but, at the same time, offers this specific ad- 
 vantage, that it enables one to determine smaller weights (up to 100 or 
 150 grammes) with the same degree of rapidity and consequently, for the 
 ordinary routine of the analyst, affords the same degree of convenience in 
 use as an ordinar}' quick working analytical balance of small carrying power. 
 
 Fitted with Prof. Dittmar's gravity-bob and reading microscope. 
 
 Beam of aluminium bronze, highly gilt and having cross-knife- 
 edge suspensions. All knife-edges and planes are of agate. The axes of 
 rotation are conveniently in sight. 
 
 No. 1. Universal -balance to carry 100 1000 grammes in 
 
 each pan, in elegant case of mahogany, walnut (or imitation) 
 Sensibility 0,1 0,01 Milligrammes. 
 
100 
 
 C. Staudinger & Co., Giessen. 
 
 No. 2. Universal balance to carry 100-500 grammes, other- 
 wise as above. 
 
 No. 3. Universal balance like No. 2 but with only one pillar 
 and in plain mahogany case. 
 
 II. Short Beam Analytical Balance in double case. 
 This new arrangement possesses the great advantage of completely- 
 protecting the sensitive parts of the balance from detrimental influences r 
 and also affords the means of weighing voluminous apparatus. The- 
 absence of the pillar has the further advantage of leaving the base- 
 entirely free for weighing operations. 
 
 Beam, pan suspensions and pans, are made of aluminium. The three 
 knife-edges and planes are of agate. The rapid oscillating beam is 
 fitted with the most perfect fixation and is provided with an arrange- 
 ment for weighing very large apparatus below the table. 
 
 Charge up to 500 grammes. Sensibility 0,10,04 Milligr. 
 
 Hr 
 
 Fig. 2. 
 
 III. Analytical Balance (Fig. 2) (with triangular beam) ; of new- 
 est and simplest construction, very suitable for students, in mahogany or 
 metal case, with marble sole, side doors and counterpoised front slide. 
 
 Beam of aluminium, pans and pan suspensions of aluminium, or of 
 nickel, or gilt brass. The three knife-edges and planes are of agate. 
 Perfect fixation for beam, pans and pan suspensions, rider scale. 
 
C. Staudinger & Co., Giessen. 
 
 101 
 
 Charges up to 200 grammes in each pan. Sensibility 0,1 Milligr. 
 Illustrated and descriptive Catalogue gratis. 
 
 B. Department 
 for Physical Apparatus. 
 
 Cathetometer (Fig. 3) 
 of newest and most perfect 
 construction, with bronze 
 prism and solid silver di- 
 vided scale one meter in 
 length. Inclinable tele- 
 scope and level. 
 
 The correction of 
 the telescope, due to 
 errors in the prism, is 
 made on the sliding 
 piece above the focus- 
 sing point of the micro- 
 scope , whereby the 
 errors of the prism are 
 directly compensated. 
 
 The prism and parts 
 are balanced by a coun- 
 terpoise, the whole re- 
 volving on a vertical axle 
 in a complete circle; the 
 prism may be set per- 
 fectly parallel to this axle 
 by means of a micro- 
 meter-screw. 
 
 Air-pumps (illustra- 
 ted by photographs) of 
 approved construction, 
 with double-acting piston, 
 self-acting valve-gear etc. 
 The whole working easily 
 and rapidly by means of 
 a fly-wheel for hand or 
 engine power. 
 
 Evacuation below l / a 
 Millimeter. 
 
 Stands of wood or iron 
 etc. 
 
 Illustrated and descript- 
 ive catalogue gratis. 
 
102 
 
 C. Staudinger & Co., Giessen. 
 
 C. Department for Forrestry and Science: 
 
 I. Heyer-Staudinger's tree-gauges of wood, acknowledged to 
 be the best existing gauge, being very light and giving veiy exact 
 results. Suitable for any climate. 
 
 Fig. 4. 
 
 II. Walking-stick gauge, made in the form of a convenient 
 forrester's walking-stick with suitable handle. 
 
 Gauges of aluminium or brass, made for the purposes of particularly 
 exact calculations. 
 
 Illustrated and descriptive catalogue gratis. 
 
C. A. Steinheil Solme, Miinchen. 103 
 
 No. 2792. 
 
 C. A. Steinheil Sohne, Miinchen. 
 
 Optical and Astronomical Works. 
 
 Dimensions are stated in terms of the metric system and of the old duodecimal 
 
 French' measure. 
 
 This establishment was founded in 1855 by the physicist Charles 
 Augustus von Steinheil, Council of Ministry and Ordinary Member 
 of the Academy of Sciences, and by his son Dr. Adolphus Steinheil, 
 at the instigation of King Maximilian II. of Bavaria, who wished to 
 perpetuate the reputation which Fraunhofer had won for the town of 
 Munich by his achievements in optical science. 
 
 In 1865 the former retired from business and his son entered into 
 partnership with his brother Edward Steinheil and established the 
 IIOAV still existing firm of C. A. Steinheil Sohne. 
 
 Charles Augustus von Steinheil died in 1870 (14. Sept.). 
 Eight years later Edward Steinheil received a sunstroke on a 
 voyage to Columbia and died in the port of St. Thomas. 
 
 The present heads of the firm are: Dr. Adolphus Steinheil, 
 the son of the founder, extraordinary Member of the Academy of Sciences, 
 and, since 1889, his son Dr. Eudolph Steinheil. 
 
 From the commencement the practical manufacture of optical com- 
 binations was based upon precursory extensive and exhaustive com- 
 putation of all optical data which were necessary for their systematic 
 production and an equally methodical system of testing served for cor- 
 rectly controlling each separate stage of their manufacture. 
 
 The following are the tests which are implied by correct and 
 systematic manufacture : 
 
 1. Critical selection of the glasses according to their chemical 
 and optical properties; 
 
 2. Determination of the properties of the glasses independently 
 of the data supplied by their makers; 
 
 3. Examination of the glasses with respect to defects which may 
 affect the combinations optically or esthetically ; 
 
 4. Calculation of the prisms and the systems of lenses so as to 
 completely determine, by pure calculation, all the elements of 
 the optical combination, (cf. ,.Handbuch der angeivandten Optik", ty 
 Dr. Ad. Steinheil and Dr. Ernst Voit, Leipzic, Teubner, 1891); 
 
 5. Measurement, by means of the spherometer constructed in 1845 
 by C. A. von Steinheil of the radius found by mechanical 
 means. 
 
104: C. A. Steinheil S5hne, Mflnclien. 
 
 6. Critical examination of the polished surfaces with respect to 
 perfection of sphericity by means of standard glasses, imper- 
 fections of the surfaces being indicated by the appearance of 
 Newton's coloured rings. 
 
 By adhering to its maxims the establishment developed rapidly 
 and the following are among its principal achievements: 
 
 1859. Establishment, in conjunction with Professors Kirchhoff and 
 Buns en, of the practical forms of the spectroscope; 
 
 1865. Construction of periscopes and of telescopic objectives with 
 flint front lens (patented in Bavaria), aplanatic lenses and micro- 
 meter oculars: 
 
 1866. Completion of the first type of the aplanatic lens (Bavarian 
 patent of 1866), which in 1867 was awarded a Gold Medal at 
 the Paris International Exhibition: 
 
 1871. Construction of wide angle aplanatic lenses at the instigation 
 of the Austrian ministry of war; 
 
 1872. Astro-photographic objectives; 
 1878. Aplanatic group lenses (patented): 
 1881. Antiplanetic lenses (several patents) ; 
 1885. Panorthic double telescopes (patented): 
 
 1887. The head of the firm was invited by the ,,AcademiedesSciences" 
 of Paris to attend the congress held with the object of dis- 
 cussing the subject of the production of photographic celestial 
 charts. On this occasion Dr. Ad. Steinheil protested against 
 the resolution carried by the majority regarding the conditions 
 which govern the production of correctly delineated charts of 
 constellations. For that resolution limited the conditions, which 
 were to be realized, to aperture, focal length and correction of 
 spherical and chromatic aberration. In pursuance of this con- 
 gress an objective having an aperture of 33 centimeters was 
 ordered by the Astro-physical Observatory of Potsdam and also 
 one of an aperture of 23.5 centimeters, which were completed 
 in September of the year 
 
 1889, and which embodied the conditions laid down by Steinheil. 
 The excellence of this objective led to 
 
 1890, a similar objective of 33 centimeter being supplied to the ob- 
 servatory of Catania in Sicily; and 
 
 1892 a similar objective of 33 centimeter achromatized for the chemical 
 rays, and also a 36 centimeter objective achromatized for the 
 visual rays, both to the Observatory of Upsala. 
 Beside these a great number of objectives of 10, 9V 2 , 9 and 8 
 inches diameter were made. 
 
 A prominent feature is also the manufacture of piano-parallel plates 
 and accurate prisms and, as a speciality, very exact piano-parallel glasses 
 and mirrors of about l / 3 millimeter thickness. 
 
 The following table contains a statistical report of the distri- 
 bution of inland and foreign export during the period 1881 to 1890: 
 
C. A. Steinheil Sohne, Miinchen. 105 
 
 Gel-many 86.59% Brought forward 90.83% 
 
 Austria-Hungary . . . 13.94% Switzerland 2.84% 
 
 France 12.62% Great Britain 2.11% 
 
 Italy 8.23% Holland 1.59% 
 
 Eussia 7.84% Denmark 0.99% 
 
 America 4.63% Sweden and Norway . 0.78% 
 
 Spain and Portugal . 3.58% Turquey and Greece . 0.45% 
 
 Belgium 3.40% Asia and Australia. . 0.31% 
 
 Carry forward 90.83% Africa 0.10% 
 
 100.00% 
 
 The continuous growth of the establishment necessitated the erection 
 of a new building plant, and on ttie 1st. March 1890 the business was 
 transferred to the new premises situated outside the town (viz. in 
 Theresienhoehe). The building occupies an elevated and isolated po- 
 sition and is provided with excellently light workshops and testing 
 rooms; among the latter there are a spacious experimental studio and 
 a testing corridore of 40 meter length. The establishment is fitted 
 throughout with low pressure steam warming pipes. The plant includes 
 a number of new machines by means of which objective lenses up to 
 1 meter in diameter may be produced. 
 
 The establishment employs about 50 men within its own precincts 
 and besides a number of others working in their own workshops. It 
 will shortly complete the 40th thousand of astronomical and photo- 
 graphic objectives. 
 
 Photographic Apparatus and Instruments. 
 
 Photographic Objectives. 
 
 Antiplanetic Lenses: German Patent No. 16354, 13. April 1881. 
 British Patent No. 1602, 12. April 1881. 
 U. S. Patent No. 241437, 10. Maij 1881. 
 
 This type consists of two entirely different parts having greatest possible 
 .aberrations of opposite sign. This plan resulted in a considerable reduction of 
 astigmatic aberration and, thereby, in uniform extension of definition and depth 
 over an increased and strictly flat area of the field. 
 
 The two pairs of lenses, the anterior one of which is positive while the 
 posterior is negative, are placed as near together as possible. The object of 
 this close proximity is uniform distribution of brightness over the entire field. 
 The great brilliancy of the antiplanetic lenses renders them particularly 
 adapted for portrait, group aud instantaneous photography and also for exposures 
 with artificial light. At the same time, these lenses have been computed in 
 such a manner as to render them capable of producing strictly flat and correctly 
 
106 
 
 C. A. Steinheil Sohne. Miinchen. 
 
 delineated images. The lenses become thus eminently suited for projection and 
 enlarging. 
 
 The original and enlarged negatives may be produced by_ the same anti- 
 planetic lens. In the latter case it is, however, necessary to reverse the lens, 
 i. e. to place it so that the posterior lens faces the original which is to be enlarged. 
 
 Enlargements of very sharply defined originals produced by this method 
 may be made to exhibit depths which are unobtainable by direct photography 
 with the same rapidity. 
 
 The dissymmetrical antiplanetic lenses are made in two types: 
 
 Series I. Portrait Antiplanet, 
 
 Relative aperture 1:4, angle 40 T 
 four lenses with positive cemented 
 anterior pair and isolated negative 
 posterior pair. The field is limited 
 as a means of obtaining unusual 
 brightness. The latter and defi- 
 nition are uniformly distributed 
 over the image and the lens 
 possesses considerable depth. 
 
 Series II. Group Antiplanet, 
 1:0, angle 60: four lenses, two 
 cemented pairs: these are placed 
 as closely together as the inter- 
 position of the diaphragm will 
 admit of. 
 
 This lens is of only moderately 
 diminished brightness as compared 
 with the preceding series, but its 
 peculiarities have been utilized in in- 
 creasing both its depth and the field 
 without diminishing its uniformity of 
 definition and distribution of light. 
 Fig. 2. These united qualities render the group 
 
 antiplanets adaptable to a great many uses, which .accounts for the popularity 
 
 of this series. 
 
 Universal Aplanatic Lenses. Relative aperture 1:6, angle 60. 
 
 These lenses originated in the endeavour of constructing objectives of the 
 same rapidity as the group antiplanets but having larger dimensions. The latter 
 type did not appear to be adapted for this purpose on account of the rapid in- 
 crease of the thicknesses of the lenses necessitated by increase of focal length, 
 and, consequently, increase of weight and diminution of rapidity. 
 
 The excellent results obtained with the new series of the rapid 
 
C. A. Steinheil Sohne, Miinchen. 
 
 107 
 
 symmetrical type led to the construction of smaller lenses of the 
 same class. 
 
 Some of the universal aplanatic lenses consist of two cemented 
 doublets, others of two cemented triplets, but in all cases the combi- 
 nation is symmetrical. 
 
 With the system of 6 lenses the principal points coincide with 
 the geometrical center of the objective, i. e. with the plane of the dia- 
 phragm. Distortion is thus obviated. 
 
 This latter feature renders these objectives particularly adapted 
 for topographic photogTammetry and for copying. On account of their 
 rapidity the universal aplanatic lenses are specially intended for photo- 
 graphy of moving objects, which demand short exposures. 
 
 The next four series of lenses are of the aplanatic type and have 
 been developed from the aplanatic prototype which originated in this 
 establishment (Bavarian patent of 1867). During these latter years these 
 lenses have been improved by the introduction of glasses which absorb 
 the chemical rays in a considerably less degfee than did the older 
 glasses. This improvement enabled the lenses to keep pace with modern 
 requirements. 
 
 Series III : Aplanatic lens 1:7; 
 angle 60. Adaptable for por- 
 traits, groups, architecture, land- 
 scape, copying and sufficiently 
 rapid for instantaneous work. 
 
 When it is required to delineate 
 plastic objects in correct proportions, 
 particularly in cases where the object 
 is not many times larger than the 
 image, these aplanatic lenses are also 
 specially supplied with very long focal 
 lengths. 
 Fig. 3. 
 
 Series IV. Landscape Apla- 
 natic Lenses 1:12 to 1:15; 
 
 field of about 75. Specially 
 constructed for landscape photo- 
 tography, but also adapted for 
 architecture and copying. 
 
 Fig. 4. 
 
108 
 
 C. A. Steinheil Sohne. Mtlnchen. 
 
 Fig. 5. 
 
 Fig. 7. 
 
 Set of 4 achromatic land- 
 scape lenses of equal aperture 
 (23 millimeter) but different focal 
 lenghts capable of combination in 
 a common mounting fitted with 
 iris-diaphragm. 
 
 Series V. Wide Angle Apla- 
 natic Lenses for architecture 
 and landscape with relative aper- 
 ture f/20 to f/25, angle of field 
 about 100. 
 
 In this lens definition, depth 
 and angle of field have been 
 greatly increased at the expense 
 of rapidity. 
 
 Series VI. Wide Angle Apla- 
 natic Copying Lenses, similar to 
 series V in point of rapidity. 
 
 By uniting greatest possible uni- 
 "form definition and brightness with 
 flatness throughout the extended field 
 this type is particularly adapted for 
 copying maps, pictures and engra- 
 vings and for photo -mechanical pro- 
 cesses. 
 
 Prisms. 
 
 For directly producing so-called 
 reversed negatives for photo -me- 
 chanical printing processes wide 
 angle aplanatic copying lenses are 
 principally used in combination with 
 rectangular prisms with silvered 
 hyp o tenus e surface . 
 
 Fig. 
 
C. A. Steinheil S6hne, Miinchen. 
 
 109 
 
 Aplanatic Focussing Lenses. 
 
 Aplanatic combination consisting of three cemented lenses, with 
 large flat field free from distortion and achromatized for intra and 
 extra-axial rays. (For further particulars vid. M. Schultze's paper in 
 Schultze's Arch. f. Mikr. Anat. Vol. II, 1866.) 
 
 Tele -photographic Objectives, 
 .T 
 
 consisting of an ordinary photographic objective (of not less than ra- 
 pidity f/7) and a magnifier achromatized for chemical and visual rays. 
 (vid. Photogr. Corresp.; Vienna, Leipzic, 1892, June and November, pp. 308 and 546). 
 
 The magnifier is a triple system of negative focus. The combination of 
 the triple system with the photographic objective of positive focus increases the 
 equivalent focal length of the total telescope objective. This equivalent focal 
 length and thus also the magnitude of the image are made to vary according 
 to the distance between objective and concave lens, which is fitted with rack 
 and pinion, the distance between the object and the objective being constant 
 during these variations. 
 
 The field of the combination measures about 10. The magnification may 
 at the expense of brightness be increased to 10 or 15, only a relatively small 
 extension of the camera being required to produce these magnifications ; the latter 
 is owing to the principal point of the combination being placed a long distance 
 in front of the latter. 
 
 The time of exposure amounts under favourable circumstances only to 
 fractions of a second, but even instantaneous exposures may be made. 
 
 The instantaneous photographic telescope , 
 
 which was first made for the German navy in 1890, appears, owing to its 
 brightness, to be specially adapted to this purpose, (vid. Dr. Ad. Steinheil's 
 paper on ,,Tele-photography" ', Phot. Corresp. Vienna, Feb. 1892). The optical 
 part consists of a double objective and a negative elongation lens, having a 
 total equivalent focus of 1.3 meter. 
 
110 
 
 C. A. Steinheil Sohne. Mflnchen. 
 
 This apparatus produces circular images of 5 centimeter diameter and is 
 particularly suitable for instantaneous photography, for marine and coast survey 
 and also for military reconnoitring and engineering from a balloon. 
 
 The entire length of the apparatus is 60 centimeters; it is provided with 
 diopter finder and instantaneous and time shutter, inurometer adjustment by 
 means of rotating ring. 
 
 Detective-Cameras 
 
 for 9X12, 12X10, 13X18 centimeter plates. Types A, B, C, D. 
 
 Type A has the focussing screen rigidly connected to the plate 
 changer. 
 
 Types B, C, D have in common with each other movable fronts 
 for accurately focussing near objects. 
 
 Type B is fitted with detachable plate changer, which has a 
 changing arrangement for plates or films similar to that of A. 
 
 Fig. 10. Type A. 
 
 Fig. 11. - Type A. 
 
 Fig. 12. - Type B. C. I). 
 
 Fig. 13. - Type B. C. D. 
 
 Fig. 14. - Type B. 
 
 Fig. 15. - Type C. 
 
 Fig. 16. Type C. 
 
 Fig .17. Type D. 
 
 Type C has a camera front combined with detachable back for 
 double dark slides. 
 
C. A. Steinheil Sohne, Miinchen. 
 
 Ill 
 
 Type D is fitted with a detachable Eastman's rollholder for 
 transparent films. 
 
 The common fronts admits of any of the three backs being used. 
 
 The detective camera is fitted with a group antiplanet (25 % 33 
 or 38 millimeter aperture) and an instantaneous and time shutter. 
 
 Stereoscopic Camera. 
 
 Fig. is. 
 
 Types A, B, C of the detective form are also made as stereoscopic 
 cameras for 8Y 2 X17 centimeter plates and are fitted with two accurately 
 paired group antiplanets (21 millimeter aperture) and stereoscopic in- 
 stantaneous and time shutter. 
 
 Pasquarelli Camera. 
 
 Fig. 20. 
 
 Fig. 21. 
 
 Detective camera with Pasquarelli's plate changer (German patent 
 No. -54014 of 30. IX. 90, Austrian- Hungrian patent 53157 18974, French patent No. 
 202525, Italian patent No. 10036, British patent No. 20009, U.S. patent No. 445232, 
 27. I. 1891) made for plate sizes 9X 12, and 6X9 centimeter and arranged 
 to take 12 plates or films. 
 
 The plates are changed and registered automatically by the simple 
 turning of a lever. 
 
 This camera is also fitted with a group antiplanet (25 or 21 
 millimeter aperture) and with instantaneous and time shutter. 
 
 By the addition to these detective cameras of rack and pinion 
 adjustment and single screw nuts they may be placed upon stands for 
 accurate focussing and quiet exposures. 
 
112 
 
 C. A. Steinheil Sohne, Miinclien. 
 
 Universal shutter 
 
 for instantaneous and time exposure, made of metal throughout, encased 
 in brass or aluminium and fitted with steel mechanism; simple and 
 quick manipulation, adjustable rapidity, precise action without shock. 
 
 Fig. 22. 
 
 The shutter opens and closes from the center. The most efficient part of 
 the objective is thus made to act throughout the exposure. It is fitted with 
 pneumatic releasing mechanism The shutter is designed for being placed partly 
 before and partly between the lenses. It is made in 5 sizes up to 52 milli- 
 meter aperture and also in the form of stereoscopic shutters with two identical 
 apertures placed 85 millimeter apart. 
 
C. A. Steinheil Sfihne, Miinchen. 113 
 
 Astronomical and Physical Instruments. 
 
 Achromatic Telescope Objectives 
 
 of short focus, brightness f/4: composed of three cemented lenses, being 
 one crown glass lens placed between two flint glass lenses, in brass mount. 
 Achromatic Double Objectives, reversion of Fraunhofer's formula, 
 i. e. flint in front, brightness f/10 to f/ 18 free from distortion (vid. 
 Dr. Ad. Steinheil's paper in the ,,Sitzungsberichte der Munchener 
 Academic der Wissenschaften" , Vol. XIX, 1889, p. 413, entitled ,,Ueber den 
 Einfluss der Objectivconstructionen etc.") 
 
 Astro -Photographic Objectives 
 
 composed of two cemented lenses made of glass w T hich absorbs only a very 
 small portion of the chemical rays, corrected for the chemical part of the 
 spectrum regardless of the position of the visual image; field 2 to 3; 
 specially constructed for sideral and seleno-photography (vid. the papers 
 of Dr. Scheiner, assistant at the Potsdam observatory, in the ,,Zeitsclirift 
 fur Instrumentenkunde" , Oct. 1891, p. 374: , } Photographische Himmelskarte" 
 and also in the appendix of the ,,Abhandlungen der Konigl. Preuss. Academic 
 der Wissenschaften zu Berlin, 1892, Sitzungsberichte, Vol. XXXII, p. 583 etc.: 
 Tin large cluster in Hercules." 
 
 Oculars. 
 
 A. Astronomical Oculars. 
 
 A D Mittenzwey Ocular; convexo-concave collective lens and 
 plano-convex eye lens; the image is formed between the lenses; field 
 about 50: free from reflections. 
 
 Achromatic Micrometer Oculars. 
 
 A F Double Ocular consisting of two achromatic objectives; 
 image before the lenses, apparent field about 40. 
 
 A G Monocentric Micrometer Ocular, consisting of three 
 cemented lenses (2 flint glass menisci and a spherical lens) ; all radii 
 struck from the same center; completely free from all reflections: 
 apparent visual field about 36. 
 
 A H Aplanatic Micrometer Ocular, also consisting of three 
 cemented lenses (1 biconvex crown lens placed between 2 flint menisci) 
 and, therefore, entirely obviating reflections; free from distortion, inter 
 and extra-axial achromatization. The image is perfectly flat and the 
 first surface is far removed from the plane of the image. For this 
 reason these oculars are specially suited for use in conjunction with 
 cross line micrometers; apparent field about 20. 
 
 8 
 
114 C. A. Steinheil Sohne, Mtinchen. 
 
 B. Terrestrial Oculars. 
 
 B D Four plano-convex lenses; images 'formed before the first 
 and between the third and fourth lenses; apparent- angle about 44. 
 
 Reading Telescope 
 
 for magnetic observations, without steel or iron; brass tube: ocular 
 supports with rack and pinion adjustment; made to focus distances 
 varying from infinity to about 4 times the focal length. 
 
 Mounted on metal tripod, swinging 30 in either direction on hori- 
 zontal axis; micrometer adjustment in azimuth with clamps and scale carrier. 
 
 All oculars are fitted with cross lines, the lowest power with 
 adjustable diaphragm. 
 
 New Shortened Telescope with Negative System. 
 
 Fig. 23. 
 
 The cone of light emerging from the short focus objective is intercepted 
 by a negative system whereby the "equivalent focal length of the objective be- 
 comes considerably larger than the length of the entire telescope. High mag- 
 nifications may thus be obtained with low power oculars and relatively small 
 dimensions. Magnification and the length of the entire telescope depend upon 
 the distance between the objective and the negative lens of certain focal 
 length; both decrease as this distance is increased. 
 
 The objective, which has a brightness of f/4 and perfectly sharp defini- 
 tion, consists of a biconcave crown glass lens cemented between two flint glass 
 menisci and has been computed together with the concave system as a cement- 
 ed system consisting of a positive flint glass meniscus and a high biconcave 
 crown glass lens. (vid. Dr. Rud. Steinheil's paper in the ,,Zeitsclirift fur 
 Instrumentenkunde" , 1892, November.) 
 
 Tube 
 
 of brass, with tubular stand, in polished sycamore case, portable and 
 of elegant appearance. 
 
 Mounted horizontally and parallactically and balanced upon cast 
 iron tripod and tubular brass pillar for standing in height of table: 
 tripod with screws for placing the pillar vertical. Vertical pillar may 
 be lengthened for astronomical observations. It may be fitted with 
 divided searching circles reading to 5 angular minutes and 20 time 
 seconds. 
 
 The achromatic double objective of the tube has an aperture of 
 61 millimeter (27'") and 73 centimeter (27") focus. The four oculars 
 give the following magnifications: the terrestrial ocular 34, the astro- 
 nomical oculars 36, 81, 108. Ocular arranged for combination with 
 
C. A. Steinheil S5hne, Miinchen. 115 
 
 sun glass and also with ocular prism of 27 millimeter (12'") aperture 
 fitted in rotating mount which may be fixed in any position, for ob- 
 serving stars in the vicinity of the zenith. 
 
 Shortened Tube with Objective System of 81 millimeter 
 (36'") aperture and 125 centimeter (46") equivalent focus. The tube 
 has a length of only 540 millimeter and is mounted upon a similar 
 stand to that of the preceeding telescope. 
 
 The terrestrial magnification is 58, the astronomical magnifica- 
 tions are 46, 92, 138, 184 and 230. 
 
 Ocular fitted with sun glass; finder of 20 millimeter (9"') aper- 
 ture and 16 centimeter (6") focus: magnification 6 X- 
 
 Telescope with one elbow, 
 
 without stand, with brass tube and ocular movement; micrometer ocu- 
 lar; objective' centering head. 
 
 A rectangular prism with silvered hypotenuse surface, in center- 
 ing mount, is placed between the objective and ocular. 
 
 The errors introduced by the prism are compensated by the 
 construction of the objective. The images are thus rendered perfectly 
 correct, (vid. Vierteljahresschrift der Astronomischen Gesellschaft, Leipzig, 1883, 
 18. Jahrgang, p. 255, paper by Dr. Ad. Steinheil on ,,the theory of 
 telescopes." 
 
 Transit prismfor taking time and polar altitudes, (vid. Kunst-u. 
 Geiverbeblatt fuer Bayern, Munic. 1885, pp. 4 13 and Astronomische Nach- 
 richten. No. 569). 
 
 Parts: Telescope of 7 millimeter (3'") aperture and 54 milli- 
 meter (2") focus; the astronomical ocular magnifies 8 times; sun glass; 
 correction in azimuth and altitude. Fitted in small handy case. 
 
 Pocket Heliotrope 
 
 for signalling at great distances, (vid. Schumacher's Jahrbuch 1844, Stutt- 
 gart and Tubingen, Cotta). 
 
 The instrument consists of a horizontal perfectly plane mirror 
 of 43 millimeter (19'") length and 27 millimeter (12"') width, the 
 silver coating of which has been removed at the center so as to leave a 
 transparent area of 3.4 millimeter (1.5'") diameter. 
 
 While sighting through this aperture an orientation image may 
 be seen of the sun which by means of the movable mirror may be 
 directed to any desired point. All points covered by this orientation 
 image are illuminated by the heliotrope. It can be recognized at a 
 distance of 50 kilometers. This instrument replaces the telescopic 
 heliotrope. 
 
 Goniometer, 
 
 for determining refractive and dispersive powers of various media and 
 for measuring the angles of prisms. Mounted upon cast iron stand 
 fitted with levelling screws. This supports a conical hollow steel 
 center which has an alhidada attached to it. A brass spindle which 
 may be rotated by hand and also by means of a micrometer screw 
 
116 
 
 C. A. Steinheil Sohne, Mttnchen. 
 
 terminates at the top in a brass dish provided with spherical hollow 
 seat. Upon this dish is placed a stage plate with spherical steel sole 
 plate by means of which the refracting edge of the prism may be set 
 perfectly vertical previous to adjustment for minimum deviation. 
 
 The common center of the spherical surfaces is situated at the point of 
 intersection of the vertical axis of the instrument and the plane of the axes 
 of the telescopes. In the focus of the objective of the slit telescope, which is 
 provided with means for setting it horizontal and which by its bearings is 
 rigidly attached to one of the feet of the tripod, is placed a Vierordt's mi- 
 crometer double slit mechanism fitted with symmetrically moving platinum lips 
 (by A. Kruess, Hamburgh, German patent No. 17092). 
 
 Fig. 24 
 
 The sighting telescope is also adjustable in the vertical plane and is 
 fitted with ocular rack and objective similar to that of the slit telescope, of 27 
 millimeter (12"') aperture and 244 millimeter (9") focus. It is provided with mi- 
 crometer oculars fitted with adjustable diaphragm, magnifying 12. 27, 45 X 
 and may be rotated about the conical steel center by means of a gun metal 
 carrier. The latter may by means of a clamping plate be fixed to the divided 
 circle. This has a diameter of 160 millimeter (6") and is divided on silver in 
 1/6 degrees. 
 
 The divisions read by th^ four diametrical alhidada verniers (60 parts 
 = 59 divisions of the limb) and by two adjustable microscopes to 10 angular 
 seconds. 
 
 (Vid. ,,Handbuch der angewandten Optik" by Dr. Ad. Steinheil 
 and Dr. Ernst Voit, Leipzig, Teubner 1891.) 
 
C. A. Steinheil Sohne, Mtinchen. 117 
 
 The goniometer may also be used as a complete apparatus for 
 spectroscopie examinations. 
 
 Large Spectrograph, 
 
 for photographing the spectra of various illuminants. Mounted paral- 
 lactically, with adjustment for correcting the polar altitude, so arranged 
 that it may easily be placed in a horizontal position for photography 
 of terrestrial spectra. By moving a single screw it is possible to 
 follow the apparent motion of the sun in cases of continued exposures. 
 The slit telescope of 34 millimeter (15'") aperture and 32.5 millimeter (12'") 
 focus is fitted with Kruess's micrometer slit mechanism with symmetrical 
 movement of the platinum lips. There are three prisms of 50 degrees and 
 47 millimeter (21"') aperture; aplanatic photographic lens of 54 millimeter 
 (24'") aperture and 61 centimeter (22") focus; spectrum 20 millimeter (9"') 
 high and about 15 centimeter (5") long extending from line A to N. To ob- 
 viate loss of light as much as possible the objective and prisms are made 
 of glasses which absorb the smallest possible portion of the chemical 
 rays. A scale may be photographed together with each spectrum. Instantan- 
 'eous shutter for short exposures. The adjustable dark slide admits of 3 or 
 more exposures being made upon the same plate. 
 
 Spectrum Apparatus according to Kirchhoff and Bunsen, 
 
 first made in 1859, specially adapted for comparing the spectra of 
 two luminous sources. 
 
 Fitted with a flint glass prism of 60, 2 telescopes of 27 millimeter (12'") 
 aperture and 24 centimeter (9") focus, magnifying 6 X> one f these being 
 fitted with slit mechanism. Scale telescope with 14 millimeter (6"') aperture 
 and 11 centimeter (4") focus. Cast iron foot. Accessories: 2 Bunsen burners, 
 2 pearl carriers with stand, description and tables for reducing values for 
 Bun sen's apparatus. t 
 
 Hollow Prism, 
 
 for determining the refractive indices of liquid media; capacity 10 to 
 11 and 15 to 16 cubic centimeter. Glass prism of 60 enclosed by 
 two perfectly plane surfaces. The prism has a cylindrical bore of 
 20 millimeter (9"') or 27 millimeter (12"') diameter passing through 
 it in such a way that its axis passes through the center lines of the 
 prism surfaces. A conical neck passes from the top of the prism to* 
 the cylindrical chamber and may be closed by an accurately fitting 
 stopper. 
 
 Both openings of the cylinder may be closed by accurately fitting piano- 
 parallel glass plates. The liquid which is to be examined is introduced by the 
 conical neck. 
 
 The covers may be removed by quickly heating the external surface. 
 To affix them it is sufficient to clean them thoroughly, to remove all traces 
 of dust and to press them upon the perfect surfaces of the prisms. 
 
118 C. A. Steinheil Sohne, Mtinchen. 
 
 Plane test glasses, 
 
 for testing perfectly plane surfaces. Glass No. I must fit II and III, 
 and II must fit III with perfect exactness. 
 
 Piano-parallel Glasses 
 
 absolutely exact, in various sizes and thicknesses. According to thick- 
 ness classified in 
 
 ordinarily thick, viz. 3 to 6 millimeter, 
 
 thin 1 to 3 
 
 thinest glasses . . about- 1/3 
 
 Piano -parallel Mirrors, 
 
 intended, in particular, for reflecting galvanometers, very thin, about 
 1/3 millimeter, in case. The piano -parallel mirrors are silvered on 
 one side and form mirrors acting through the glass. The silver is coat- 
 ed with a protecting layer. 
 
 Rectangular crown glass prisms 
 
 with square cathetus surfaces, with sharp edges, absolutely correct 
 angles and without pyramidal defects. 
 
 Triple Rutherford Prism. 
 
 Example of dimensions: Aperture of the polished surfaces 27 to 
 34 millimeters (12'" to 15'"), consisting of a thallium prism of 90 
 cemented between two crown glass prisms of 20, which not only pro- 
 tect the surfaces of the thallium from oxydation but also renders it 
 possible to make the refracting angle of the thallium prism so large 
 that without the addition of the crown glass prisms total reflection 
 would take place. 
 
 Aplanatic Magnifying Lenses. 
 
 These are so formulated as to possess considerable focal 
 distance and to give an undistorted image achromatized in the central 
 and extraaxial parts of the field (vid. M. Schultze's paper in Schultze's 
 Arch. f. mikr. Anat. V. II, 1866.) 
 
 Aplanatic lens of 95 millimeter (42'") equivalent focus: linear 
 magnification about 2*/ 4 ; large flat field suitable for examining maps etc. ; 
 in polished mounting. 
 
 Set of 6 aplanatic magnifying lenses with holder in case. 
 The mounting consists of a simple blackened ring. 
 Equivalent foci: 61 41 27 18 13 9 millimeter, 
 
 27 18 12 8 6 4 lines, 
 Magnifications 3.5 5.3 8 12 16 24 
 Set of 5 aplanatic lenses in folding mount; in case: 
 Equivalent foci: 41 27 18 13 9 millimeter, 
 
 18 12 86 4 lines, 
 Magnifications 5.3 8 12 16 24 
 
C. A. Steinheil Sohne, Mtlnchen. 119 
 
 Terrestrial Telescopes. 
 
 Hunting draw telescope 
 
 in bronzed brass mounting, two draws and sun shade; 34 millimeter 
 (15'") aperture and 32 centimeter (12"). focus magnifying 15 times, 
 particularly bright field. 
 
 Leather case and tree screw. 
 
 Panorthic Monocular 
 
 with object glass of 16 millimeter (7'") diameter and very large field. 
 Polished aluminium or nickeled brass mounts. Total length 
 28 millimeter, weight about 12 grammes and 21 grammes respectively; 
 for pocket or strap. They may be used with equal advantage by hy- 
 permetropic, myopic or normal sighted persons. The linear magnifi- 
 cation is about 1.6. These telescopes are not adjustable by draws 
 and have to be adjusted for each individual eye. For this purpose 
 the indication of the spectacle number required for correcting the eye 
 for distance is sufficient for the selection of the proper focus. 
 
 Panorthic Double Telescopes 
 
 (Jumelles) with double distance of lenses. (German patent No. 28787.) 
 
 (Examplified by one of magnification 4.4 with object glass of 
 47 millimeter (21" / ) ( li ame ter and 12 glasses. Aluminium mount and Eussian 
 leather cover. Double draw,s and adaptable to width of user's eyes.) 
 This special form of Galileo's telescope is particularly distinguished 
 from all other existing forms in . that its achromatization is of a higher 
 order and that, consequently, the definition is greater. Even when the 
 instrument is placed at an angle to the normal direction brillantly 
 illuminated objects sharply set off by the back ground show hardly any 
 coloured fringes. 
 
 The ratio of the magnification of the telescope to the size of the 
 field is, in spite of these points of excellence, not less, in many cases 
 even greater than with other types. There are, <as a rule, 8 glasses 
 in a double telescope of this kind. Of these, two cemented lenses form 
 the objectives, while the oculars consist of two lenses separated by a 
 short distance. Only in the case of relatively high magnifications 
 (4.4X) each of the ocular lenses consists of two cemented lenses; in 
 this case the double telescope contains 12 lenses. 
 
120 Emil Sydow, Berlin NW. 
 
 [No. 2794. 
 
 Emil Sydow, Berlin NW. 
 
 13, Albrechtstrasse. 
 
 University Mechanician and Optician, Maker of Ophthalmic 
 
 Instruments. 
 
 Speciality: Ophthalmoscopes, Laryngoscopes, Reflection mirrors. 
 Awarded several Gold and Silver Medals and Diplomas* 
 
 Motto: ,Ein Mann, der recht zu wirken denkt, 
 Muss auf das beste Werkzeug halten." 
 Goethe. 
 
 I. Complete Set of Standard Test Lenses; solid walnut case 
 lined with red velvet. Double scale. Lenses ground and numbered in 
 terms of dioptra; mounted in gilt or silver-plated frames, fig 1, on page 121. 
 (Catalogue No. 133). Cylindrical lenses partly greyed for quickly finding 
 the axis. Lid of case made to readily open. 
 
 II. The same set in rose-wood case, inside polished ebony. Lid of 
 case made to readily open. 
 
 III. The same set. Case of solid walnut throughout. Eemovable lid. 
 
 IV. Military Spectacle Test Case, No. II, as used by the German 
 Army Administration; made of oak, exactly according to the direction 
 of the military autorities. Fig. 2. (Catalogue No. 139.) 
 
 Fig. 2. (Catalogue No. 139.) 
 
 Ophthalmic Instruments: Liebreich's Large Stable Ophthalmoscope; 
 Demonstration model on stand, fixing to table, complete; mahogany case. 
 Ruete's Ophthalmotrope. Large demonstration model. 
 
 Stockes's Variable prism; indicating 130. Stenop. Variable 
 Hand Folding Glass. 
 
Emil Svdcnv. Berlin NW 
 
 121 
 
122 Emil Sydow, Berlin NW. 
 
 Gerloff's Orthoscope. Burchard's Stereoscope. Placido's 
 Keratoscope. Galezowski's Strabometer. Horstmann's Strabo- 
 meter. Laurence's Strabometer. Glass strabometer. Schweigger's 
 muscle gauge. Snellen's International Colour Scale with spectacles. 
 
 Burchardt's International Sight Tests. Schweigger's Sight 
 Tests. Snellen's and also Nieden's Sight Tests. Dr. Louis Wolffberg's 
 Relievo Plates; Edition 1893. Dr. Louis Wolffberg's Apparatus for 
 Colour Diagnosis. Wolffberg's Perimeter objects. 
 
 Electrical Apparatus. Schweigger's newest Electrical 
 Ophthalmoscope, with adjustable incandescent light. 
 
 (Entirely new 1893 pattern) 
 Latest Electrical Cornea Lens, excellent for direct illumination 
 
 Schweigger's Binocular Electrical Ophthalmoscope (Latest 1893 
 pattern.) 
 
 Sciascopes: Schweigger's Sciascope. Latest form. 
 Roth's , " . 
 
 Wolffs , ... aluminium. 
 
 Roth's Sciascope and Phacometer (New). 
 
 Refraction Ophthalmoscopes : Knapp's Refraction Ophthal- 
 moscope. 
 
 Schweigger's and Loring's Refraction Ophthalmoscope. 
 
 (Latest form with toothed wheels) 
 Roth's Refraction Ophthalmoscope. 
 
 (Entirely new automatic pattern) 
 Patented in Germany, D. R. P. No. 66215. 
 
 (Unsurpassed construction.) 
 
 Burchardt's Refraction Ophthalmoscope, combining all test lenses 
 contained in the spectacle case and going even beyond these. 
 
 Loring's, Morton's, Lyder's and Borthen's, Hirschberg's (two 
 patterns), Julers's, de Wecker's, Landolt's, Noyes's, Haab's. 
 Swanziger's, Grossmann's and various other Refraction Ophthal- 
 moscopes. 
 
 Test Spectacles: Light! Of Aluminium! Light! 
 
 Burchardt's Universal Spectacle, with toothed wheel adjustment; 
 excellent instrument for all occurring measurements. 
 
 Gutman's Universal Spectacle. 
 
 Nachet's, Schweigger's, Burchardt's and other Universal 
 Spectacles. 
 
 Perimeters: Pedrazzolfs Perimeters (New entirely original 
 construction). 
 
 Foerster's Perimeter. Blix's Self registering- Perimeter. 
 
Ernil Sydow, Berlin NW. 123 
 
 Schweigger's Hand Perimeter, extremely practical (560 sold), fig. 3. 
 (Catalogue No. 162.) 
 
 Fig. 3. (Catalogue No. 162.) 
 
 Laryngoscopes. Various Reflectors of aluminium mounted in 
 bronze. 
 Copper plated Laryngoscope. 
 
 Laryngoscopic sets. Illuminating lamps. 
 
 Lenses: Hartnack's Spherical Lens, with two powers mounted 
 together. 
 
 Hartnack's Spherical Lens, Bruecke's and Zehender's Lenses. 
 Various specimens. 
 
 Miscellanea: Hilgendorf's Auxanograph. Apparatus for sketch- 
 ing small natural objects. 
 
 New Automatic Plugging mallet, with elbow joint. 
 Selle's Microscope Mirror. 
 
 Luxurious Special Catalogue Gratis on Application. 
 
124 ' Ludwig Tesdorpf, Stuttgart. 
 
 No. 2795. 
 
 Ludwig TeSdOrpf, Stuttgart. (Wuerttemberg.) 
 Maker of Scientific Precision Instruments. 
 
 Adress for. letters: L. Tesdorpf, 81 Augustenstrasse, Stuttgart. 
 Telegraphic address: ,,Tesdorpf, Stuttgart." 
 
 SPECIALITY: 
 
 Astronomical Surveying Instruments of the most advanced 
 type and highest degree of excellence. 
 
 The firm was established in 1881. > Flighest references. Export 
 to all countries. Instrument maker to many home and foreign govern- 
 ments. Now exhibiting at International Exhibition for the first time. 
 
 For want of space only surveying instruments are being exhibited. 
 But also portable anfl stationary transit instruments, universal astrono- 
 mical instruments, refractors with and without parallactic mounting., 
 telemeters (for measuring distances for coast defence) are made in 
 the works. 
 
 The firm undertakes the manufacture of scientific instruments of 
 precision according to drawings and sketches. 
 
 Catalogues in German and french of all the instruments made in 
 the works may be had gratis and post-free on application. 
 
 No. 1. Tachygraphometer , Wagner and Tesdorpf's latest 
 type. This instrument, which is intended for speedily working out 
 general and detailed plans, is particularly adapted for land-surveying, 
 rail-way, canal, road and military surveying. The apparatus is 
 only apparently complicated; in actual use it is extremely simple as 
 regards its manipulation. (See Fig. 1.) 
 
 Theory of the instrument: The instrument described in the following 
 paragraphs solves all problems, with which other tachymetrical theodolites 
 have to be worked out by calculation, automatically by purely graphical means. 
 It dispenses with the calculation of the coordinates of the positions of the 
 staves (by the tachymetrical formula E D . cos 2 a from the oblique distance 
 measured with the telescope and the divisions sighted on the staff). The hori- 
 zontal distances from the center of the instrument to the position of the 
 staff and also the absolute elevation above the sea-level are directly 
 projected without the assistance of tables or slide-rules. (By slightly 
 pressing upon the needle apparatus the readings are instantaneously transferred 
 to the paper, in any desired scale 1 : 500, 1 : 1000, 1 : 2000 etc.) 
 
 / Description of the principal parts: 
 
 1. The upper body. The tachymeter itself, which is mounted upon a 
 metal base-plate P opened in the center, rests upon three ivory wheels, 
 which can be adjusted vertically and run in accurate guides. The pillar in the 
 center supports the telescope and the distance scale A. 
 
 2. The telescope mounted on horizontal trunnions, clamp and vertical 
 micrometer adjustment; adjusted for central transit, fitted with new distance 
 
Ludwig Tesdorpf, Stuttgart. 
 
 125 
 
 measuring ocular constructed on Reichenbach's principle with adjustable web: 
 objective of 32 millimeter diameter magnifying 36; reversion level with sensi- 
 bility of 12 sec. 
 
 3. Distance scale A: connected with the telescope, reading to milli- 
 meters to both sides of the zero point; the divisions on the right hand side 
 of the zero point are used when the telescope is placed in its usual position, 
 the divisions on the left hand side are to be considered when the instrument 
 is used as a transit- theodolite. 
 
 Note: Upon this scale the distance pointer B fitted with automatic spring 
 stop is made to slide easily. With reductions of 1 : 1000 distances of 210 to 
 230 meters can be taken, with reductions of 1 : 2000 these distances may, 
 therefore, vary from 4:20 to 460 meters. 
 
 Fig. i. 
 
 4. The pointer B, which slides along the distance ruler A, is fitted with 
 two verniers. The lower vernier serves to adjust the distance read off the 
 distance rod, the latter being throughout divided in decimeters and centi- 
 meters. The upper vernier is made to rotate and is fitted with special vertical 
 correction and is so arranged that with any position and inclination of the 
 telescope the divisions of the projection triangle R are automatically closely 
 approached by the vernier as soon as the triangle is raised. 
 
 Note: When the vernier is on the zero point of the scale A the edge of 
 the upper vernier coincides exactly with the center of the telescope axis. 
 
 5. Scale F affixed to P, reading to 1 millimeter, for taking the hori- 
 zontal projection of the oblique distance adjusted by scale A. 
 
126 Ludwig Tesdorpf, Stuttgart. 
 
 6. Scale G on the base-plate P, with controlling divisions reading to 
 1 millimeter and vernier, serving as guide for the sliding-piece K with needle 
 apparatus. 
 
 7. Projection triangle R, running on wheels with automatic spring 
 stop. By means of this triangle the oblique distance adjusted by scale A is 
 projected with the aid of a vernier upon scale P. 
 
 Note I: The vertical scale of this triangle, which reads to 1 millimeter, 
 is not numbered, on account of the great variability of the elevation; heights 
 from 10 to 10 millimeters may, however, conveniently be marked upon the 
 celluloid strip let in for this purpose with lead-pencil and these notations are 
 again easily removed. This vertical scale may be used without changing the 
 notation for differences in height, provided the differences of level between two 
 points of observation do not exceed 15 meters (being 15 millimeters of the 
 scale divisions). 
 
 Note II: The projection triangle has at its underside a lug projecting 
 downwards which fits into a cavity in the sliding piece K; this causes the 
 needle apparatus to describe always the same path along the divided ruler F. 
 The readings of scales F and G must, therefore, always agree. 
 
 8. Sliding-piece K is attached to the needle apparatus. The latter 
 serves to transmit the projection of the distance taken by scale A to the 
 drawing paper. 
 
 9. The wheels. By means of these and a box bubble placed within the 
 pillar the apparatus is levelled. 
 
 Note: The three axes of rotation of the wheels intersecting in the 
 common center of the apparatus, which lies exactly vertically below the center 
 of the telescope axis and at the front edge of the base-plate, the apparatus 
 rotates freely round this point (the zero point of the adjustment). By means 
 of a break attached to one of the wheels the position of the apparatus may be 
 fixed at any moment. 
 
 10. Centering ruler. This serves to maintain an unchanged adjustment 
 of the instrument while several readings are being taken from one point. This 
 ruler, which has a round projection and diaphragm, is held down upon the 
 paper with the right hand. While taking hold of the pillar with the left hand 
 and moving the instrument with its corresponding round cavity towards the 
 ruler the apparatus may be freely rotated round this center. 
 
 Note I: The center of the round cavity, into which the centering-ruler 
 is inserted, lies exactly vertically below the center of rotation of the axis of 
 the telescope. 
 
 Note II: When all the verniers are in their zero positions, then also 
 
 1. the edge of the triangle E must coincide with that of the rotating 
 vernier of the sliding piece B. 
 
 2. the needle point of the sliding piece K must be exactly above the 
 center of the round cavity at the front edge of the base-plate P. 
 
 The under- structure : Principal parts: Stand with Tesdorpf 's Tripod 
 Levelling Arrangement, clamp and micrometer levelling adjustment with hori- 
 zontal tribrach base-plate. 
 
 Circle: 10 centimeter diameter, reading to 1/2 degrees, with 2 verniers 
 reading to 1 minute. 
 
Ludwig Tesdorpf, Stuttgart. 127 
 
 Upper sole-plate: tribrach, upon which the apparatus may be mounted 
 in a two-fold manner: 
 
 1. for use as a tachy metrical theodolite, in all cases where the 
 tachymeter is screwed directly upon this plate; 
 
 2. for use as a tachymetrical transit theodolite, in cases where the 
 surveying-table M is brought into requisition. 
 
 Surveying-table M with rollers S and ratched wheels A for conveniently 
 stretching the drawing-paper. 
 
 Note: Upon one of the rollers the finished drawing is rolled up, whilst 
 the other roller deals out fresh paper. The rollers are for this purpose made 
 to move laterally in order that in such cases where the drawing envolves con- 
 siderable curves it may be displaced sufficiently to I'eep the vertical pressure of 
 the apparatus near the axis of the lower structure. 
 
 Vid. Jordan, Zeitschrift fiir Vermessungsivesen u . 1886. Heft 14 and 16. 
 
 No. 2. Large Compass Theodolite with repeating arrangement. 
 Horizontal limb of 20 centimeter diameter, with hood and glass -covers 
 above verniers. Vertical circle of 17 centimeter diameter of opening. 
 Both circles divided on silver in 1/6, reading by verniers to 10 sec. 
 directly or 5" by estimation. The vertical circle has besides / divisions, 
 and its rim is divided by deeply cut lines in 1/2 throughout; figured 
 in terms of zenith distance for better finding fixed stars for geographical 
 orientation. The compass has a needle of 12 centimeter length. The 
 telescope is made to freely revolve on its axis ; it has an aperture of 33 
 millimeter and magnifies 36 times; there are two oculars (1 orthoscopic 
 and 1 inverting ocular for zenith readings), and 2 sun-shades; the telescope 
 axis is traversed by webs, fitted with lamp at side and central reflector 
 for illuminating the field. Crossed levels on alhidada of horizontal limb. 
 Alhidada level with micrometer adjustment for altitude circle; striding 
 level with correction screws resting upon carneol cylinders. Mounted on 
 English model stand. See Fig. 5. 
 
 Packed in two cases of polished walnut, containing also plummet, screw- 
 driver, camel-hair brush and lubricating oil. 
 
 No. 3. Repetition Theodolite. Horizontal spoked circle of 17 centi- 
 meter diameter, vertical circle of 12 centimeter diameter, divided on silver 
 in 1/3, two verniers reading to 20'', by estimation to 10". Both circles 
 with metal hood and glass covering. Telescope magnifying 30 times. 
 Diameter of objective 32 millimeters. Orthoscopic ocular. Telescope- 
 level, pillar-level and striding level. Alhidada level for the altitude circle. 
 Tesdorpf's tripod horizontal adjustment. See Fig. 4. 
 
 Packed in polished walnut case, with necessary fittings and stand. 
 
 No. 4. Compass Theodolite, similar to No. 5. Horizontal circle 
 12 centimeter diameter, divided in 1/3: vertical circle of 10 centimeter 
 diameter divided in 1/3, reading to 20". Compass needle of 5, 5 centi- 
 meter length; lamp. Tripod with Tesdorpf's horizontal adjustment. 
 Stand and case. See Fig. 2. 
 
 Note: The Theodolites No. 2. 4. 5. 6. have besides divisions in %. 
 like No. 20. 
 
128 
 
 Ludwig Tesdorpf, Stuttgart. 
 
 Under structure of the theodolites with respect to 
 
 the arrangement of circles, axes and Tesdoipf's horizontal 
 
 tripod adjustment. 
 
 Fig. 4. 
 Theodolite No. 3. 
 
 Fig. 5. 
 Theodolite No. 2. 
 
Ludwig Tesdorpf, Stuttgart. 
 
 129 
 
 9 
 
130 
 
 Ludwig Tesdorpf, Stuttgart. 
 
Ludwig Tesdorpf, Stuttgart. 131 
 
 No. 5. Compass Theodolite with Repeating Arrangement, 
 Horizontal circle 15 centimeter diameter. With hood and glass covering. 
 Divided on argentan in 1/6, reading by 2 verniers to 10". Vertical 
 circle of 12 centimeter diameter, divided in 1/3, reading by 2 verniers 
 to 20". Compass with needle of 10 centimeter length, dial divided 
 in Vi - Telescope with 2 oculars (1 orthoscopic, 1 inverting for zenith 
 readings) with 2 sun -shades. Magnifying 24 times. Alhidada level on 
 the horizontal circle. Pillar level, alhidada- level for the vertical circle- 
 with micrometer adjustment; telescope -level. Case and English model 
 stand, lamp for illuminating the cross -hairs; distance measuring scale* 
 1:100. Tripod with Tesdorpf's horizontal adjustment. 
 
 No. 6. Cofnpass Theodolite. Travelling theodolite, similar to 
 No. 4. Horizontal circle of 10 centimeter diameter, divided in 1/2 r 
 reading to 1 minute; vertical circle of 8 centimeter diameter, divided in 
 1/2, reading to 1 minute. Compass needle of 4.5 centimeter length; 
 dial divided in 1/1 ; 2 oculars; telescope magnifying 20 times; lamp. 
 Patent horizontal adjustment. Case and stand. (See Fig. 2.) 
 
 No. 7. Small Travelling Theodolite. Tachymeter - theodolite. 
 Divisions on argentan. Both circles of 8 centimeter opening, divided in 
 1/2, reading to 1 minute, or 30" by estimation. Telescope magnifying; 
 21 times with objective of 20 millimeter diameter. Box bubble; pillar,, 
 telescope and striding levels. Detachable Compass with parallel ruler; 
 length of needle 7 centimeter. Patent horizontal adjustment. Case and 
 English model stand. 
 
 No. 8. Precision Levelling Instrument. Telescope with hard 
 cast rings resting upon carneol prisms, magnifying 36 times ; orthoscopic 
 ocular. Centering objective. Horizontal clamp with fine adjustment. 
 Elevation screw for conveniently and quickly adjusting the reversion level 
 (of 6 sec. sensibility) attached to the side of the instrument. Tripod 
 horizontal adjustment. (See Fig. 6.) 
 
 No. 9. Patent Precision Levelling Instrument. Telescope with 
 hard cast rings resting on carneol prisms. Magnifying 24 times. The 
 reversion level (Sensibility 6 10"), which is visible in the ocular field, 
 is protected from heat, sun-light or other extraneous influences 
 in general by metal hoods fitted with ground glass windows; these allow 
 the level to be illuminated in a manner which is most pleasant to the 
 eye. By throwing the hoods back the level may be used in the ordinary 
 way. Mounted upon Patent horizontal adjustment. (See Fig. 8.) 
 
 Note respecting Nos. 8 and 9: These instruments, fitted with re- 
 version-levels, have, as compared with other designs fitted with de- 
 tachable or reversible levels, the important advantage that they dispense 
 with the inconvenience of adjusting the level, also with the reversion of 
 the telescope in its bearings. 
 
 These instruments, which are intended for most accurate measurements, 
 can be used without preliminary careful adjustment. The manipulation is sim- 
 plified in the same degree that the accuracy is increased. The manipulations 
 consist in: Adjustment of the level: position I (level on the left); rotation of 
 the telescope in its bearings through 180; second adjustment of the level: 
 position II (level on the right). " 
 
 9* 
 
132 Ludwig Tesdorpf, Stuttgart. 
 
 The arithmetical mean of both readings on the rod gives 
 the true horizon. 
 
 On the same principle also larger instruments are made magnifying 
 30, 36 and 60 times. 
 
 No. 10. Levelling Instrument with fixed telescope mounted on 
 long vertical axis horizontal fine adjustment; telescope of astronomical 
 magnification 30 ; level of sensibility of 13" per interval of 2 millimeter. 
 Mounted on stand with Patent horizontal adjustment. English model stand. 
 
 No. 11. The same without fine adjustment; terrestrial magni- 
 fication 20. 
 
 No. 12. Levelling Instrument with fixed telescope mounted upon 
 long vertical axic. Horizontal fine adjustment.* A Telescope with 
 astronomical magnification 21. Patent horizontal stand adjustment. 
 
 No. 13. The same without clamp and fine adjustment ; astronomical 
 ocular 21. 
 
 Note: If a terrestrial ocular be used the magnification, the tube 
 length being the same, will be 14. 
 
 No. 14. Universal Levelling Instrument with elevation screw; 
 telescope magnifying 21 times; horizontal circle of 8 centimeter diameter, 
 divided in 1/2, reading to 1'; on light stand, Canvass case. 
 
 No. 15. The same, without circle, on a lighter stand, in case. 
 See Fig. 14. 
 
 No. 16. Patent Pocket Levelling Instrument (Wagner's). 
 Telescope magnifying 18 times; reversion -level encased and protected 
 from external influences; bubble directly visible in field of ocular; mounted 
 upon light stand. In leather case. See Fig. 7, 9, 10, 11. 
 
 No. 17a. The same, with telescope magnifying 12 times; on 
 light stand. 0.5 centimeter can be conveniently read off at a 
 distance of 100 meters. Degree of accuracy: ^QO f the distance. 
 
 No. 17 b. The same, with telescope magnifying 12 times, in case. 
 
 No. 18. Universal Instrument, for general plans. Patent 
 Schmalkalden Compass with prism, lens and folding - sights, circle 
 divided in 400, reading to single grades or 20' by estimation: telescope 
 magnifying 12 times; surveying level of sensibility of 20" fitted 
 with hinged mirror for convenient reading; altitude arc divided in 1/2 
 grades, reading to 1', besides / divisions. Degree of accuracy: 5 milli- 
 meter per 100 meter distance. In polished walnut case. See Fig. 15. 
 
 No. 19. Instrument for Chain and Compass Survey. 
 
 Small handy instrument for limited areas, The instrument is fixed 
 upon a rod; it is fitted with patent Schmalkalden compass; circle 
 divided in 360 reading to 1, by estimation to 12'. 
 
 For measuring rise and fall in terms of % the diopter instrument 
 No. 20 will be found useful. 
 
 No. 20. Diopter instrument. Type I. Hand instrument with 
 handle; in case, sail-cloth or leather, as preferred. 
 
 Altitude arc divided in %, viz. 050% "reading 1%, 50100% 2%. 
 
Ludwig Tesdorpf, Stuttgart. 133 
 
 The levelling bubble a, (fig. 16) being projected by reflection into the 
 diopter tube may in a moment be brought into its horizontal position during 
 the sighting operation without changing the position of the eye; the level is 
 during this process brought into play by the milled head e. 
 
 Bubble a and the pointer are rigidly connected and may be rotated to- 
 gether by means of the milled head. 
 
 During each sighting operation this milled head is turned until the bubble 
 appears upon the metal mirror fixed at 45 inside the diopter tube in a sym- 
 metrical position with respect to the horizontal cross web. The corresponding 
 altitude can be read directly off the altitude arc. 
 
 h = scale of percentages reading to 1/ , 
 
 i scale divided in 1/1 reading, by vernier to 10 minutes. 
 
 No. 21. The same. Type II, to fix on staff, with horizontal axis 
 and vertical trunnions, extremely serviceable for general preliminary work 
 or subordinate cross sectional measurements. 2 divisions, for direct reading 
 of rise and fall in percentage. In case with rod. 
 
 No. 22. The same. Type III, combined with small horizontal 
 circle of 7 centimeter diameter, divided in single degrees, reading to 2', 
 sights as in No. 20. In polished walnut case. 
 
 No. 23. Percentage Clinometer and Hand Levelling Instrument. 
 Combination of No. 20 with telescope magnifying 12 times. This 
 instrument has, like Nos. 9 and 17, the front of the ocular fitted with 
 a second lens for viewing the reflected image of the bubble, whereby it 
 is possible to sight the bubble and object simultaneously. See Fig. 16. 
 
 No. 24. Patent "Schmalkalden" Compass for holding in band 
 or for screwing upon staff: in leather case. 
 
 No. 25. Hypsometer. Handy instrument for general forest survey, 
 in particular for forest valuation. This instrument may be used for simple 
 levelling, measurements of heights and distances. Degree of accuracy: 5/ . 
 
 .No. 26. Pantometer for limited areas. Horizontal circle reading 
 to 2', with compass and adjustable sights; in polished walnut case. 
 
 Note : Instead of the usual hairs the instrument is provided with 
 metallic sight webs. See Fig. 13. 
 
 No. 27. Optical Square, simple form. Large size. 
 No. 28. . Small 
 
 No. 29. ,, , with three mirrors for setting off angles 
 
 90 and for ranging lines. 
 
 No. 30. Prismatic Square, in case. 
 
 No. 31. ,, , watch form, in case. 
 
 No. 32. Box bubble for screwing to levelling rod; accessory 
 to. Nos. 1. 
 
 No. 33. Box compass; declination compass; accessory to No. 1. 
 
 No. 34. Cartometer with three wheels, in case, This instrument 
 serves, like the planimeter, for computing boundaries. See Fig. 17. 
 
134 Ludwig Tesdorpf, Stuttgart, 
 
 Fig. IT. 
 Cartometer No. 34. 
 
 No. 35. Cartometer with 5 wheels, in case. 
 No. 36. The same, with 7 wheels, in case. 
 
 These patent cartometers serve for computing the lengths of lines 
 of any form, curves, spirals, serpentines etc. 
 
 Special features of the apparatus: (No. 3436.) 
 
 1. Greatest simplicity of manipulation and great accuracy. 
 
 2. Lines can be traced backwards and forwards without interruption, the 
 wheels being alternately thrown in and out of gear according to the direction 
 in which the apparatus is made to follow the lines. 
 
 The absolute length L results immediately from the product of the 
 arithmetical mean (m) of the tracings made by the instrument with 3, 5 or 
 7 wheels and the constant K attached to each particular instrument. 
 
 L = m. K. 
 Example : 
 
 1st tracing Position of wheels before, N t after tracing, N 2 
 
 II nd tracing N 3 N 4 
 
 thenN 2 -N 1= ,n, and = ^_^ 
 
 N 4 N3 = n n 
 No. 37. Pachymeter for measuring the thicknesses of me.tal, 
 
 paper, card board, for workshop use. Reading directly to 0.005 mm; 
 measuring up to 5 mm. 
 
 No. 38. Pachymeter, larger size. Divided wheel of 85 mm 
 diameter, with reversible jaw, suitable for cartridge manufacture. Reading 
 directly from 0.005 to 5.0 mm. 
 
 No. 39. Protactor ruler, made of argentan, semicircle of 20 cm 
 diameter, divided in 360: l / 2 Q , reading to 2' with ruler 0.5 m long. 
 Clamp and fine adjustment. 
 
 No. 40. Protractor for tachymetrical surveying (radial ruler 
 without centration), with special adjustment of the magnetic deviation. 
 
 No. 41. Xylometer, apparatus for determining the specific gravity 
 of various species of wood; for scientific determination of the qualities 
 of woods. 
 
 No. 42. Hand Compass, mounted upon staff, with ball and 
 socket joint, and vertical axis of rotation. 
 
 No. 43. Bertram's Heliotrope, mounted upon wood base. 
 (Signalling apparatus for long distance surveying.) 
 
Wilhelm Uebe, Zerbst-Anhalt. 
 
 135 
 
 No. 2796. 
 
 Wilhelm Uebe, Zerbst-Anhalt. 
 
 Maker of Chemical and Physical Glass Instruments. 
 
 Exporter of thermometers of all kinds, and Glass goods for 
 clinical purposes. 
 
 Speciality: Self-Registering Fever Thermometers, with Abso- 
 lutely Indestructible Index. 
 Clinical Maximum Thermometers. 
 
 Minuten-Aerzte-Haxima-Thermometer 
 
 Clinical Minute Maximum Thermometers, 
 made of Jena standard glass. 
 
 The scale backed with red to facilitate reading. Graduated accord- 
 
 en Minufen -Thermometer 
 
 D.R.Qebr.M.N?5676 
 
 ing to Centigrade or Fahrenheit's scale. With certificates. In elegant 
 nickel, ebonite, aluminium or finest leather cases. Also with certificates 
 of the Imperial Physical and Technical Institute in Charlottenburgh. In 
 all existing forms. Absolute^ reliable workmanship. 
 
136 Wilhelm Uebe, Zerbst-Anhalt, 
 
 Tongue Minute Thermometers, 
 
 D. E. Gebr.: Registered Design No. 5676, with horse-shoe mercury 
 bulb, exactly fitting the under-side of the tongue; very practical and. 
 highly commended by autorities. 
 
 Bath, Window and House Thermometers. 
 
 Thermometers with movable scale. Pro vis. German Patent. 
 
 Sole Maker: Wilhelm Uebe, Zerbst-Anhalt, 
 Maker of chemical and physical glass instruments. 
 
 Artificial Glass Eyes. 
 
Voigt &: Hochgesang. Gottingen. 137 
 
 No. 2797. 
 
 Voigt & Hochgesang, Gottingen. 
 
 Principal: R. Brunnee. 
 
 Makers of Cry stallographic- Optical Instruments. 
 
 Microscopically thin sections of rocks. 
 
 Minerals, Fossils etc. 
 
 I. 
 
 Microscope N. 1 A (Fig. 1) constructed according to suggestions of Prof. 
 C. Klein 1 ) for advanced mineralogical and petrographic research. 
 This instrument is fitted with the most recent and perfect apparatus for 
 all possible measurements in parallel polarized and convergent light. 
 The circle, which is made of a suitable alloy, is divided in half degrees. 
 The verniers read to single minutes. The circle is surmounted by a, 
 mechanical stage with scales and divided heads for reading and noting 
 its position. The polarizer is so arranged that quick changes may be 
 made from polarized to convergent light. 2 ) A second polarizer with very 
 large Nicol prism and highly refracting set of lenses and an objective 
 of numerical aperture 1.53 render the microscope available for measure- 
 ment of minerals of very low refractive power. The Bertrand lens 
 is fitted with rack and pinion. The optical equipment of the microscope 
 consists of the objectives Nos. 0, 1, 2, 4, 5, 7, 9, oculars Nos. 1 and 4 
 with micrometer, Nos. 2 and 3 with cross lines, Bertrand's ocular, 
 Oalderon's ocular, screw micrometer ocular, Babinet's compensator 
 ocular, one dark ground Nicol prism, one quartz wedge, selenite, quartz 
 and 1/4 undulation mica-plate. 
 
 The above described Microscope is exhibited in the exhibition of 
 German Universities. 
 
 In the Collective Exhibition, Group 21, the following instruments 
 and appliances are exhibited: 
 
 Microscope No. i B. made according to the suggestions of 
 Prof. Klein, for mineralogical and petrographical research. 
 
 The construction of this instrument is precisely the same as that 
 of No. 1A, excepting that it is not fitted with mechanical stage and 
 that the circle is divided in whole degrees only, the vernier admitting 
 of reading to Vio degrees. 
 
 The instrument is supplied with objectives Nos. 1, 2, 4, 7, 9 and 
 oculars Nos. 2 and 3 with cross lines, Nos. 1 and 4 with micrometer, 
 screw micrometer ocular, quartz, mica and selenite plate. 
 
 *) Vid. Nachrichten von der Ktfnigl. Gesellschaft der Wissenschaft zu 
 Go'ttingen 1884, No. 11, p. 434 etc. Neues Jahrbucli far Mineralogie, 1883, 
 I. Heft 2. Mikroscop. Physiogr. der petr. wichtig. Mineralien v. H. Rosenbusch 
 1887, I. p. 120; 1892. I. p. 126. 
 
 2 ) Zeitschrift ftir Instrumentenkunde. 1891. April. 
 
138 
 
 Voigt & Hochgesang. Gottingen. 
 
 Fig. 1. A. Microscope. 
 
Voigt & Hothgesang, G&ttingen. 139 
 
 II. 
 
 Prof. O. Lehmann's Crystallization Microscope 1 ) (Fig. 2) for 
 observing the formation of crystals at high temperatures, also during 
 incandescence and electrolysis. 
 
 The stand is fitted with two stages revolving about the optical 
 axis. The lower stage is completely covered and is divided in 360. 
 The upper stage may be adjusted independently of the lower stage. 
 
 Three mirrors serve as polarizer, two of these being fixed, while 
 the illuminating mirror, for quickly changing the illumination, is capable 
 of rotation. 
 
 The burner is firmly attached to the foot but can be moved aside; 
 the air and gas supply is regulated by two screw-valves. Several blow- 
 tubes may be attached to the stage for rapidly cooling preparations or 
 objectives. For the examination of incandescent preparations a special 
 objective is used; it is provided with a double casing through which a 
 constant stream of cold water is made to flow. The preparation is placed 
 upon a separate stage and rests upon 4 thin platinum points, whereby the 
 loss of heat by conduction is minimized. The specimen may also, by means 
 of two platinum wires, be connected with two ebonite mercury cups which 
 are connected with the poles of a small battery. For electrolytical ex- 
 periments at low temperatures another stage, supplied with the microscope, 
 is used. If required the instrument may also be provided with a polariz- 
 er fitted with a lens combination. In this form it may also be used as 
 a mineralogical microscope proper. 
 
 ~ III. 
 
 A Collection of 115 thin sections of minerals of petro- 
 graphic interest, prepared with special regard to the system of crystals 
 and mounted according to crystallographic directions. The collection 
 contains also crystals with certain surfaces for goniometric measurements. 
 
 This collection was compiled according to a pattern [collection 
 arranged by Prof. Klein. 
 
 IV. A Collection of 100 thin sections of eruptive-rock types. 
 To each section is appended a sample of the corresponding rock provided 
 with one polished surface. 
 
 This collection is compiled according to Eosenbusch, Microscop. 
 Physiogr. 1887 and may be supplemented by 250 other rock-specimens. 
 
 1 ) vid. 0. Lehmann. Die Krystall analyse 1890; 0. Lehmann. Molecular- 
 physik L 1888. II. 1889. 
 
140 
 
 Voigt & .Hochgesang, Gottingen. 
 
 Fig. 2. Crystallization Microscope. 
 
Voigtlaender & Sohn. Braunschweig. 141 
 
 No. 2798. 
 
 Voigtlaender & Sohn, Braunschweig. 
 
 Optical Works. 
 
 (Photographic Objectives, Binoculars and Terrestrial Telescopes.) 
 
 The Optical Works of Voigtlaender & Sohn were founded by 
 Christoph Voigtlaender in Vienna in 1 756. In the days of the founder 
 and his son, Frederick, the principal business consisted in the manufacture 
 of spectacles, reading glasses, simple microscopes and hand-telescopes, in 
 particular those of the Galileo type. This, according to present views, 
 simple department of optical industry received a considerable impetus 
 when Frederick Voigtlaender in the beginning of this century began 
 to grind periscopical spectacle lenses and in 1811 constructed the first 
 Binocular on the principle of Galileo's telescope. At that time, however, 
 public requirements were too modest to encourage manufacture on a large 
 scale; at the same time the unsatisfactory quality and the optical unifor- 
 mity of the glasses which were then available and also the absence of 
 satisfactory mechanical means greatly impeded the development of optical 
 instruments. 
 
 Not until Fraunhofer, in the first quarter of this century, taught 
 how to produce homogeneous gUsses capable of variation with respect 
 to their optical properties and suitable for optical combinations and how 
 to determine their optical constants with scientific precision, did it become 
 possible to make decided progress in the development of optical instruments. 
 
 The third representative of the firm, Frederick Voigtlaender, 
 soon mastered and adopted Fraunhofer's methods and with a spectro- 
 meter, which he made himself, determined the refractive and dispersive 
 powers of all available glasses. This enabled him to compile optical data 
 for the computation of optical instruments; he utilised this knowledge 
 with the greatest success and supplied the mathematician Prof. Petzval 
 of Vienna with the data respecting the available glasses for the calculation 
 of a photographic doublet. According to the calculation of Prof. Petzval, 
 Frederick Voigtlaender, in 139, made the first photographic doublet 
 and thus inaugurated the era of photography, which within 50 years has 
 made greater strides in its development, in the improvements of the 
 methods and means which it envolves, and in the extension of its appli- 
 cation to the purposes of art and trade than perhaps any other branch, 
 of industry. 
 
 The portrait lens, owing to its rapidity, furnished the first means 
 for the photography of living objects. It differed so much in its con- 
 structive elements and in its optical powers from any optical system 
 that had been produced previously, that it formed the basis of an entirely 
 new class of optical instruments. 
 
142 Yoigtlaender & Sohn, Braunschweig. 
 
 In the earlier part of the period to which we have alluded, viz 
 in the years 1840 to 1860, photography spread very slowly; its methods 
 were intelligible to only a small number of the scientifically educated; 
 moreover the photographic lens of that time still possessed a serious 
 fault, the difference of the chemical and optical foci, which, though 
 apparently an easily curable defect in its practical consequences yet 
 greatly retarded the popularity of photography. 
 
 In 1856 the firm succeeded in eliminating this defect by introducing 
 another glass so as to form a compensating element. Shortly after the 
 Collodium process became Known, and it may be said that at this time 
 portrait photography began seriously. Also the Orthoscope, the first 
 landscape lens, which possessed a larger field, became only then practi- 
 cally useful; though its construction had been in the possession of the 
 firm as early as 1841. 
 
 A few years after the publication of the first photographic lens 
 an improvement was also made in the construction of the binoculars 
 by the introduction of triple objectives and triple eye-pieces, whereby better 
 means w r ere obtained for the compensation of spherical and chromatic 
 aberrations and also for the increase and aplanation of the field. These 
 binoculars with 12 glasses became, particularly in England, very popular, 
 more especially so when the firm some 30 years ago took up the manu- 
 facture of the mounting of the binoculars in brass and aluminium. The 
 variety of these binoculars is very large indeed. Binoculars are made 
 magnifying only 2V 2 to 4 times for the theatre, and of higher power, 
 magnifying up to 8 times, for out-door use. These are mounted in a great 
 variety of forms, as the catalogues shc^jv (No. 1 to 56). 
 
 In the course of years, however, the firm had to yield to the variety 
 of the demand, in particular to that of the German Navy, for optically 
 more simple marine glasses with double objectives and single eye-pieces, 
 containing, therefore, only 6 lenses. Accordingly such simplified binoculars 
 with a large and bright field are now made and supplied to nearly all 
 fleets of the world, in particular to the German Navy, the U. S. Navy 
 and a special form with rapid movement to the Artillery of the German 
 Army. Among the exhibits will be found a sample of this latter binocular, 
 5000 of which have recently been ordered by the German Army-admini- 
 stration, and also the aluminium model which has been adopted by the 
 War Department in Washington. 
 
 While these binoculars were being improved and introduced to the 
 public, attention was also paid to the improvement in the construction 
 of hand-telescopes with terrestrial eye-pieces. These also are made by the 
 firm in various sizes, with object glasses from 1 inch to 2V 4 inch diameter, 
 magnifying 14 to 36 times, fitted either with one drawer of the form 
 adopted by the German navy, made of nickeled German silver, or with 
 three draw-tubes of brass and aluminium for sporting and military purposes. 
 
 As long as the collodium process held the monopole, photography 
 remained almost exclusively in the hands of professional photographers. 
 The invention of dry plates opened the field to the amateur about 15 years 
 ago. These greatly simplified out-door photography; landscape and archi- 
 
Voigtlaender & Sohn. Braunschweig. 143 
 
 tectural photography became the most popular branches of amateur 
 photography. For these purposes, however, the portrait lens, with its 
 different degrees of rapidity was not very suitable, owing to its limited 
 field. Frederick von Voigtlaender, the fourth and present head of the 
 firm, subsequently constructed in 1877 the Euryscopes, symmetrical 
 lenses which gave a large flat and bright field quite free from distortion. 
 These lenses having rapidly become popular, various successive 
 
 F F 
 
 series were constructed of relative apertures ^r, -^r and Wide Angle 
 
 lenses of relative aperture -^. These correspond to the series IV, VI, VII 
 and VIII of the present catalogue. The advantages of the symmetrical 
 lenses suggested also improvements in portrait lenses, and in 1883 the 
 long focus portrait lenses were replaced by symmetrical Portrait Eury- 
 scopes. (Series II and III of the catalogue). 
 
 Until comparatively recently opticians had only a limited range of 
 optical material at their disposal. The series of available glasses was 
 uniformly graduated according to the percentage of lead contained in the 
 glasses. The optical properties of these glasses varied monotonously: 
 a higher percentage of admixed lead always resulting in higher refractive 
 and dispersive powers. 
 
 Great changes were effected in this direction when Prof. Abbe 
 and Dr. Schott established the Jena Glass Works and in 1886 published 
 their new glasses. The production of these new glasses influenced the 
 optical industry in a similar manner, though to a much greater extent, 
 as did Fraunhofer's 7 glass-fusions. In the new series practical opticians 
 found at last glasses, whose optical properties appeared to be paradoxical; 
 there were glasses of high refraction and low dispersion and there were 
 others of high dispersive and low refractive power; within certain limit 
 it was even possible to couple any desired dispersion with any given 
 refractive index. 
 
 Messrs. Voigtlaender & Sohn have been the first opticians who 
 utilized this extension of the optical means in as much as they comple- 
 tely reformulated in 1888 their symmetrical lenses, which until then had 
 contained two flint-glasses, and replaced the latter by two extremely 
 transparent crown-glasses. The Rapid Wide Angle Euryscope Series V, 
 the W. A. Euryscope Series VII and the Single Landscape Lenses IX 
 were introduced as new species of photographic lenses. 
 
 Although all these new constructions embodied great improvements 
 in definition and covering power, yet it was not possible with the symme- 
 trical objective TO compensate thoroughly astigmatic aberrations, the chief 
 defect of wide angle lenses. By employing a totally dissymmetrical com- 
 bination of pairs of glasses of normal and abnormal properties the firm of 
 CarlZeiss of Jena has recently succeeded in almost completely eliminating 
 this last defect. Since the spring of 1891 Messrs. Voigtlaender & Sohn 
 have by friendly arrangement with the firm of Carl Zeiss, added to their 
 older series these Zeiss Anastigmatic lenses, of which 6 series classified 
 
 F F i 
 
 according to their relative apertures from - 4 to jg are now made. 
 
144 Voigtlaender & Sohn. Braunschweig. 
 
 This addition, to their former series, of wide angle lenses with flat and 
 anastigmatic field fills the last gap which had been felt. 
 
 The entire list of objectives of various classes made by the firm 
 forms a most complete selection of lenses for all purposes and satisfies all 
 the wants of professional, amateur and scientific photographers. 
 
 In the 137 years of its existence the firm has steadily grown and 
 always kept pace with the requirements of the time by utilising improved 
 methods and einploj'ing the best modern machinery. The works in Brunswick 
 include new extensive buildings provided with high and spacious work- 
 shops electrically illuminated by own machines and accumulators. The 
 firm employs now about 100 men. A hall of 120 square meters area 
 has been reserved for examining and testing binoculars and telescope?, 
 and a studio having an area of 100 square meters has been set apart 
 for testing photographic lenses. The conditions of illuminations are so 
 favourable in these spaces as to render experiments therein independent 
 of the differences of light. 
 
 The lenses are ground by machinery, whilst the polishing, which 
 is controled by standard lenses, is mainly effected by hand, in order to 
 avoid the detrimental effects of heating to which large lenses are exposed, 
 if polished by machinery, and also to obtain the means of individual 
 correction. - A speciality of the works consists in their Ramollir or 
 remoulding plant, in which they press or mould their own lenses. This 
 plant consists of a double totally independant set, thus warranting to 
 carry on the work without interruption. Each plant consists of a preli- 
 minary heating and annealing oven and the pressing oven. Being 
 thus independant of other glass works the firm is in a position to effect 
 any order without loss of time. 
 
 The U. S. A. Agents of the firm are: 
 
 For Photographic lenses: Messrs. Benjamin French & Co. 
 
 319 Washington Street, Boston. 
 
 For Binoculars and Hand-telescopes: Messrs. Tiffany & Co. 
 
 Union Square, New- York. 
 
Carl Zeiss, Jena. 
 
 No. 2801. 
 
 Carl Zeiss, Jena. 
 
 Optical Works. 
 
 A. Microscopes and Microscopical Accessories. 
 
 Complete Series of apochromatic objectives and compensating 
 
 eye -pieces. , 
 
 i Complete Series of achromatic objectives and Huyghenian 
 
 eye -pieces. 
 
 Accessory apparatus for testing objectives. 
 Complete Series of Microscope Stands. 
 Apparatus for projection and photo -micrography. 
 Microscopes for crystallographic and petrological research. 
 Illuminating apparatus for white and for coloured light. 
 Spectroscopic eye -pieces. 
 
 Apparatus for measuring and counting microscopical objects. 
 Dissecting microscopes and magnifiers. 
 
 All as described in the Catalogue of Microscopes and 
 Microscopical Accessories. (Catalogue No. 29, 1892, German, English 
 and French editions.) 
 
 B. Photographic Lenses, Zeiss Patent Anastigmats, Six Series. 
 
 Series I, 1 
 
 4,5, equivalent focus 130 354 mm (5 14 in.) 
 
 Series 11,1 6,3, 85-590 (3,3-23,6 ) 
 
 Series III, 1 7,2, 96-586 (3,8-23,1 ) 
 
 Series IVa, 1 9, 120820 (4,8-65 ) 
 
 Series IV, 1 12,5, 62906 (2,5-35,7 ) 
 
 Series V, 1 18, 86-946 (3,437,3 ) 
 
 All as described in the Catalogue of Photographic Lenses, 
 
 1891, and Supplement, 1892. (German, English and French editions.) 
 
 C. Optical Measuring Instruments for scientific and 
 technical purposes. 
 
 Abbe's Spectrometer and accessory apparatus. 
 
 Abbe's Large Refractometer. 
 
 Percentage Refractometer. 
 
 Refractometer for determining the percentage of salt in 
 
 sea-water. 
 Refractometer for special technical purposes (Butyro- 
 
 refractometer). 
 Cry stal-refractometers . 
 Contact-Micrometer. 
 Small Comparator. 
 
 10 
 
146 * Carl Zeiss, Jena. 
 
 Spherometer. 
 
 Focometer, apparatus for measuring the focal lengths of 
 
 systems of lenses. 
 Fizeau-Abbe Dilatometer. 
 Apparatus for demonstrating the optical connection between 
 
 diffraction spectrum and the image of an object. 
 All as described in the Catalogue of Optical Measuring 
 Instruments, 1893. (German, and English editions.) 
 
 Historical and statistical notes. 
 
 The firm of Carl Zeiss was founded in 1846 by Dr. Carl Zeiss, 
 who died in 1888. At present upwards of 500 persons are employed in 
 the optical and mechanical workshops (incl. the foundary, joiner's shop, 
 smithy etc.) in the exclusive manufacture of optical instruments and 
 apparatus for purely scientific and fine technical purposes; viz. 
 microscopes and their accessories, photo -micrographic apparatus, photo- 
 graphic lenses and optical measuring instruments of various kinds. 
 
 The gross value of the annual production in these goods has since 
 several years exceeded one million Marks. About one half of the goods 
 remain in Germany, the other half is for export. The latter extends 
 to all countries in and beyond Europe where scientific work is done. 
 
 There are three departments, viz.: 
 
 1. Microscopic and Photo-Micrographic Department. 
 
 2. Photographic Lens Department. 
 
 3. Department of Optical Measuring Instruments. 
 
 These departments are under one commercial management, but are 
 each under the supervision of scientific specialists. The scientific, tech- 
 nical and commercial staff consists in all of 20 persons. There are, at 
 the present time, 3 general directors, viz. Prof. Abbe, Dr. Schott 
 and Dr. S. Czapski. 
 
 Until 1875 Mr. Carl Zeiss was the sole proprietor of the works. 
 In that year Prof. Abbe, who had been associated with the establishment 
 since 1866, became a partner, and in 1881 Dr. Roderich Zeiss, the 
 eldest son of the founder, entered as third partner. After the death 
 of Dr. Carl Zeiss his son retired from business in 1889, and the Optical 
 Works were handed over in 1891 to the ,,Carl Zeiss Memorial' 4 in 
 Jena, which had been founded by Prof. Abbe in 1889 for the promotion 
 of scientific and social aims. 
 
 Since the 1st July 1891 the establishment has ceased to be private 
 property. It transacts its business on account of the ,,0arl Zeiss Me- 
 morial", which is endowed with the legal powers of a person and whose 
 representative is the Government of the Grand-dukedom of Saxony. 
 
 The Jena Glass Works (of Schott & Genossen), which are 
 affiliated with the Optical Works, having been founded in 1884 by 
 Dr. Otto Schott in conjunction with the then proprietors of the firm of 
 Zeiss, are since 1891 joint property of Dr. Schott and the ,,Carl 
 Zeiss Memorial". 
 
Paul Gebhardt, Berlin S. 
 
 147 
 
 No. 2803. 
 
 Paul Gebhardt, Berlin S., 
 
 85 & 53 Prinzenstrasse. 
 
 Mechanician and Optician. 
 
 Established 1870. 
 
 Factory and Ware-house of scientific, physical, electrical, 
 
 optical, mechanical and chemical 
 apparatus and appliances for class-demonstration. 
 
 List of Exhibits: 
 Mechanics: 
 
 System of 2 X 3 brass pullies, with stand and weights. 
 Model of a crane, of metal, with double gear. 
 Hydraulic press with brass cylinder. 
 
 Large double barrelled air- 
 pump (Fig. 1) with Babi- 
 net's cock, glass cylinders 
 and vacuum-gauge. Acces- 
 sories: Barometer test,, 
 dasymeter, Magdeburg 
 hemispheres of brass. 
 Mercury shower with 
 cock and mercury-bottle 
 with screw on stand. 
 Apparatus for demon- 
 strating propagation of 
 sound in vacuum, elec- 
 trical, with recipient, and 
 binding-screws. 
 
 Iron Centrifugal machine, horizontal and vertical, adjustable. Also: 
 
 2 balls of unequal weight. 
 Watt's regulator. 
 
 10* 
 
148 
 
 Paul Gebhardt. Berlin S. 
 
 Acoustics: 
 
 Stopped lipped pipe. 
 
 Reed-pipe with reed striking upwards, funnel and 
 
 glass window, stopped lipped pipe with divided 
 
 sliding rod. 
 
 Cagniard la Tour's Syren, with tachometer. (Fig. 2) 
 Tuning fork on sound-board. 
 
 Telephones for demonstration or use, one of these 
 dissectable. 
 
 Fig. 2. 
 
 Optics: 
 
 Simple goniometer (graduated arc and radial stop). 
 Glass prism, mounted on adjustable stand. 
 
 Spectroscope with flint glass prism, comparison prism, slit, sighting 
 and scale telescope. 
 
 Heliostat with clock-work. 
 
 Model telescope for demonstration, with lenses and diaphragms in 
 skeleton frame. 
 
 Newton's Coloured Rings Apparatus, in brass mount. 
 
 Heat: 
 
 Muschenbrock's Lever 
 Pyrometer (Fig. 3), 
 with 3 different metal 
 rods, for demonstrating 
 the expansion of metals 
 by heat. 
 
 Sectional model of a 
 steam-engine cylin- 
 der and valve-gear. 
 
 Fig. 3. 
 
Paul G-ebhardt, Berlin S. 
 
 149 
 
 Fig. 4. 
 
 Electricity: 
 
 Compound magnet (2 bar-magnets with arma- 
 ture). Magnet Needle on stand. 
 
 Declination and inclination compass (Fig. 4), 
 
 on brass stand with levelling screws, divided 
 
 circle , micrometer adjustment and needle 
 with agate cap. 
 
 Gold-leaf electroscope, with condenser discs. 
 Self-exciting Electrical Induction Machine with 
 
 one fixed and one revolving disc; powerful. 
 
 Fulminating tube, Fulminating plate, 
 Rotating globe on isolated stand, 
 Smoke condensing apparatus. 
 
 Bertram's galvanometer with silvered 
 dial. (Fig. 5) 
 
 Motor for rotating Geissler's tubes, with tube. 
 
 Morse apparatus with clock-work and keys. 
 
 Apparatus for rotating a movable magnet 
 round a stationary circuit, a magnet 
 round its own axis and a movable 
 circuit round a magnet. 
 
 NEW! Apparatus for demonstrating the 
 galvanic current surrounding a fixed 
 magnet, with commutator. 
 
 Du Bois-Reymond's induction apparatus. 
 
 Simple induction coil. 
 
 Rumkorff Induction-coil, with condenser and commutator; also 
 
 Geissler tube and holder. 
 
 Geissler tube with uranium-glass figure, on stand. 
 Automatic carbon-regulator with reflector for electrical light. 
 
 Miscellanea: 
 
 Gravert's combined Wool-gauge and dynamometer, Menzel's Wool- 
 gauge. Hartmann's Wool-gauge, Thaer-Kleinert's Wool-gauge. 
 
 Illustrated descriptive catalogues may be had gratis and post-free. 
 Physical and Chemical Laboratories supplied ivith complete outfit,' and special 
 estimate worked out. 
 
150 Gr.-duc. Standardizing Institute for Glass Instruments, Ilmenau (Thur.). 
 
 Nr. 2804. 
 
 Grand-Ducal Standardizing Institute for Glass 
 Instruments, Ilmenau (Thuringia). 
 
 This Institute was founded in 1889 by the Government of the 
 Grand-dukedom of Saxe -Weimar with the cooperation of the Imperial 
 Physical and Technical Institute in Charlottenburgh. Its immediate aim 
 was to support the manufacture of thermometers in the Thuringian States 
 by officially testing and standardizing thermometers, an undertaking in 
 which the Imperial Institution in Charlottenburgh had already been 
 engaged on a larger scalei The business of the Institution developed 
 in a most satisfactory manner, to such an extent, indeed, that already 
 in the first year the number of thermometers tested and certificated 
 amounted to more than 20000. At the present time, i. e. the beginning 
 of 1893, the number of the tested instruments of this kind exceeds 
 already 80000. 
 
 The Institute extended its operations also to the development 
 and encouragement of the manufacture of instruments within the Thu- 
 ringian States, in particular, that of accurate measuring instruments. 
 The Institute possesses, thanks to the liberality of the grand -ducal 
 government, for this purpose a collection of valuable appliances. 
 
 The Government has also planned the erection of a technical 
 school for glass-blowers and glass-instrument makers, and probably this 
 plan will be carried out in the course of this year (1893). 
 
 The Institute has recently undertaken to test lactometers, lacto- 
 butyrometers , hydrometers for sulphuric acid and saccharometers , also 
 graduated glass measures, with the exclusion of those instruments which 
 are under the control of the Government Assize Department. 
 
 To facilitate the export trade in standardized instruments the 
 Institute supplies certificates with translations in the English, French, 
 Italian, Spanish, Russian, Dutch, Swedish and Danish languages. 
 
 In the thermometric tests the Institute enjoys the cooperation 
 and stands under the control of the Imperial Physical and Technical 
 Institute and affixes to the certificates both its own seal and that of 
 the latter institute. 
 
 The Institute exhibits the following samples of its own manufacture : 
 
 1. A Standard Thermometer for temperatures from 30 to 100 0., 
 each degree being divided into 10 parts; a Chemical Standard 
 Thermometer with scale division ranging from 100 to 200 0., 
 each degree being divided into 5 parts, and with mark indi- 
 cating the zero point; a Chemical Standard Thermometer 
 with scale ranging from 200 to 300 C., divided into half 
 degrees, and marks indicating boiling and zero point. 
 
Gr.-duc. Standardizing Institute for Glass Instruments. Ilmenau (Thur.). 151 
 
 2. 11 Hydrometers for determining 1 the specific weight of sul- 
 phuric acid, with range of scale of 10 units of the 2nd decimal, 
 divided into units and half units of the 3rd decimal. 
 Beside these the Institute is exhibiting a collection of Glass 
 Instruments and Apparatus, which have been entrusted to its care 
 by the subjoined firms. The data respecting the business capacity 
 of these firms have been supplied by their respective representatives. 
 
 I. Alexander Kuchler & Sohne, Ilmenau (Thuringia). 
 
 Makers of Glass Instruments of great accuracy. 
 
 Specialities: 
 
 a) Thermometers of the highest degree of accuracy for scientific and 
 technical purposes, with or without certificates from the Govern- 
 ment Testing Institutes at Charlottenburgh and Ilmenau; 
 
 b) Hydrometers for all purposes: accurately adjusted according to 
 the standards of the Government Testing Institutes, also with official 
 certificates ; 
 
 c) Graduated Measuring Instruments of all kinds, Warranted, also 
 with official certificates. 
 
 The following samples are exhibited: 
 
 1. Syphon and Cistern Barometers; 
 
 2. Various Maximum and Minimum Thermometers for dwelling 
 houses and windows, Contact Thermometers, Bath and Brewer's 
 Thermometers ; 
 
 3. Standard, Chemical and Clinical Thermometers; 
 
 4. Hydrometers of various kinds; 
 
 5. Geissler's and Crookes's Apparatus, various kinds and designs. 
 
 Those exhibits which bear the mark | K | are accom- 
 
 panied by official certificates of the Institutes of Char- 
 lottenburgh and Ilmenau. 
 
 After the close of the exhibition all the instruments are to be sold at a 
 high discount. Please to address the manufacturers, Messrs. Alexander Kuchler & 
 Sohne, Ilmenau (TJmringia, Germany). 
 
 II. Alt, Eberhardt & Jaeger. 
 
 Thuringian Glass Instrument Works with Branch Works of 
 Keiner, Schramm & Co. in Arlesberg nr. Elgersburg (Thuringia) 
 and Glass Works in Schildhorst nr. Kreiensen. 
 
 This firm was founded in 1873 and has since made steady 
 progress (last year's turn -over: M. 750000). It employs altogether 
 about 450 hands and possesses in Ilmenau new work- shops provided 
 with excellent accommodations and fitted with the best machines. It 
 obtained several awards in exhibitions. The firm maintains a large 
 
152 Gr.-duc. Standardizing Institute for Glass Instruments, Ilmenau (Thur.). 
 
 stock of the goods which it manufactures and also undertakes, on a 
 small commission, to purchase for transatlantic buyers all articles be- 
 longing to its own class of goods which are supplied in the German 
 market. The registered trade mark of the firm of A. E. & J. is a 
 
 ,,Human eye", thus: "tS^"'~ All articles sent to the Exhibition bear 
 
 4.E.J. 
 this mark. 
 
 The firm is capable of supplying extensive orders and manufactures 
 a great variety of glass instruments and appliances; it also supplies 
 goods made according to special design and is also prepared to supply 
 large quantities of whole-sale goods. 
 
 Beside the glass-house, the blow pipe and graduating work-shops, 
 there are also departments for grinding, turning, wood -working and 
 packing-case making. 
 
 The firm makes and supplies: 
 
 1. All kinds of Thermometers for technical, chemical and clinical 
 purposes, thermometers for dwelling-rooms, windows and bath- 
 rooms, travelling thermometers, in numerous forms, with or 
 without official certificates. 
 
 2. Hydrometers of any kind, Saccharometers, Lactometers, Acid- 
 hydrometers and Alcoholometers, with or without official certi- 
 ficates. 
 
 3. Barometers of any kind and design. 
 
 4. Appliances for demonstration purposes in schools and Uni- 
 versity Colleges. 
 
 5. Apparatus for the equipment of Laboratories; also those 
 made of porcelain, sheet -iron, tin, platinum, nickel, copper, 
 wood etc. 
 
 6. All kinds of Apparatus for Chemical and Physical Labora- 
 tories, for Sugar-refiner's and Brewer's laboratories. 
 
 7. Graduated Goods; e. g. Graduated Measures, Gas burettes, 
 Hydrometers etc. 
 
 8. Glass-goods for Clinical and Surgical, and for Microscopical 
 and Bacteriological purposes. 
 
 These various groups are represented by exhibits. 
 Ihe General Catalogue of the firm comprises 18 special priced catalogues. 
 Telegraphic address: ,,Glasalt Ilmenau". 
 
 III. Ephraim Greiner, Stuetzerbach (Thuringia). 
 
 Glass Works, 
 
 with departments for the manufacture of glass holloAv-ware and tubing, 
 glass-blowing, standardizing, accurate grinding and etching; with own 
 joiner's and turner's work-shops. 
 
 Exhibits : 
 
 1. Thermometers for clinical, chemical, pharmaceutical, brewing, 
 distilling, dairy and technical purposes and for private and domestic use. 
 
Gr.-duc. Standardizing Institute for Glass Instruments, llmenau (Tliur.). 153 
 
 2. Alcoholometers, Hydrometers, Saccharometers, for chemi- 
 cal laboratories and many branches of industry. 
 
 8. A few Appliances for the Analysis of Gas and Smoke. 
 
 4. Various Appliances and Instruments for lactometric purposes. 
 
 5. A number of Appliances and Instruments for Chemical , 
 Physical, Pharmaceutical, Educational and other purposes. 
 
 6. Various Burettes, Pipettes, Graduated Glass-measures, 
 Lactometer-flasks, Graduated Boiling-flasks, Acetometers, Acedi- 
 meters (for tartaric acid), Albuminometers, Einhorn's Saccharometers 
 for fermented fluids and mash - acid hydrometer. One nest of 
 Evaporating Dishes and one set of Boiling Beakers with and 
 without .spout. 
 
 IV. Emil Gundelach, Gehlberg (Thuringia). 
 
 Glass Works: Glass hollow-ware for chemical and technical 
 purposes made of glass capable of resisting, in a high degree, the corro- 
 
 Fig. 1. 
 
 Fig. 2a. 
 
 Fig. 2. 
 
 sive action of chemicals, such as Beakers, Boiling-flasks, Retorts, Spe- 
 cimen-bottles, Cylinders, Bell-jars, Glass-tubing of all kinds etc. 
 
154 Gr.-duc. Standardizing Institute for Glass Instruments, Ilmenau (Thur.). 
 
 Glass Instrument Works: All Apparatus and Appliances for 
 Chemical, Physical and Commercial purposes, such as graduated goods 
 and volumetric appliances and apparatus for gas-analysis, mercury air- 
 pumps, apparatus for demonstration etc. etc. 
 
 Incandescent Lamp Works: Only such lamps are made which 
 are used for demonstration or clinical, astronomical and optical pur- 
 poses, for the illumination of closed hollow bodies of any kind or for 
 decorative purposes. 
 
 The Factory supplies its own gas and is provided with gas- 
 engine power. 
 
 Exhibits : 
 
 1. A Collection of Graduated Appliances. Graduated flasks 
 Avith auxiliary scale on the neck, fig. 1, for quickly and accurately 
 reading the pouring mark; graduated pipettes and full-pipettes (adjusted 
 to deliver one precise quantity), among these so-called poison-pipettes", 
 fig. la, provided with india-rubber collar and suction-tube ; a few burettes 
 and graduated flasks with certificates by the Standardizing Institute at 
 Ilmenau. 
 
 
 Fig. 2b. 
 
 Fig. 3. 
 
 Fig. 4. 
 
 2. Graduated Burette with 2 cocks and a flask containing the 
 liquid, fig. 2: Brink's, Mohr's, fig. 2a, and Gay-Lussac's burettes, 
 fig.2a, the latter with glass loop protecting the outlet jet from breaking off. 
 
Gr.-duc. Standardizing Institute for Glass Instruments, Ilmenau (Thur.). 155 
 
 Part of the graduated flasks, Gay-Lussac's burettes and a few 
 of Mohr's burettes are backed by a white enamel stripe with dark 
 middle line, by Schellbach's process. Viewed through the meniscus 
 formed by the liquid this dark middle line appears deeply incised and 
 thus, especially with the aid of a mirror, as in the case of the burette 
 shown in fig. 2, a very exact reading may be taken. The same result 
 is attained by double graduation. 
 
 3. Part of Pflueger's Mercury Air- 
 pump for physiological purposes (analysis 
 of blood-gas), fig. 3. 
 
 4. Gas Washing Bottle, with inlet 
 funnel acting also as a safety tube, fig. 4. 
 
 5. Molinari's Apparatus for milk-fat 
 analysis, fig. 5. 
 
 6. Capronica's Apparatus for estimat- 
 ing nitrogen in urine (Ureometer), 
 fig. 6. 
 
 7. Soxhleth's Fat Extraction Appa- 
 ratus, fig. 7. 
 
 8. Foerster's Fat Extraction Appa- 
 ratus, fig. 8. 
 
 9. Various other appliances and one 
 set of Boiling Beakers. 
 
 10. A set of Incandescent Lamps for 
 demonstration and decoration. 
 
 Pig. 7. 
 
 V. Franz Schilling, Gehlberg (Thuringia). 
 
 Glass Works: Glass Hollow-ware and Glass Instruments. 
 Exhibits : 
 
 1. Graduated Appliances for Analytical Measurements: Bu- 
 rettes, Pipettes, SchifTs Burettes, Cylindrical Graduated Measures, 
 Graduated Flasks. 
 
 2. Apparatus for Gas-analysis : Appliances for determination 
 of carbonic acid, Alkalimeters, Bunte's Burettes (Jueptner's modi- 
 fication), Winkler's Gas-burettes (Hempel's modification) and Hempel's 
 Gas-pipettes. 
 
156 Gr.-duc. Standardizing Institute for Glass Instruments, Ilmenau (Thur.). 
 
 3. Muencke's and Dr. Norblad's Gas Generating Apparatus. 
 
 4. Apparatus for the estimation of nitrogen in urine. 
 
 5. Broegger-Harada's Apparatus for separating minerals con- 
 tained in heavy solutions (with large cock of 15 to 20 mm bore). 
 
 6. Mercury Air Pump, own construction (small size). 
 
 This pump excels over other pumps in the following respects: 
 
 a. It works conveniently and is reliable. By repeatedly lifting 
 and lowering the mercury vessel successive evacuations are 
 obtained without the necessity of alternate^ opening and 
 closing cocks. A valve in the mercury pressure vessel pro- 
 tects the puihp from being broken in the event of careless 
 lifting ; 
 
 b. The Dehydrating Apparatus is simple in its construction. It 
 is to be charged with anhydrous phosphoric acid and consists 
 of a simple bulb, which is ground to fit directly into the 
 shell of the cock, so that it may be taken off without ne- 
 cessitating the removal of any other part of the pump. The 
 cock is so constructed that one turn disconnects the dehy- 
 drating apparatus, so that the pump may also be used without 
 the latter. The pump has the further advantage that it may 
 be safely and easily packed for transport as it is composed 
 of small separate parts. 
 
 7. Various Appliances, a Collection of Glass-cocks (exact re- 
 productions of Geissler's cocks), samples of Glass tubing, Beakers and 
 Boiling flasks. 
 
 VI. H. R. Lindenlaub, Schmiedefeld in Thuringia. 
 
 Glass-blowing and Glass Instrument Works; manufactures 
 Thermometers, Hydrometers and Glass Appliances of any kind 
 and excels in the manufacture of Radiometers and Geissler's Tubes. 
 
 Exhibits : 
 
 1. Geissler's Tubes. 
 
 2. Eadiometers of various kinds, Radiometers registering the 
 number of rotations. 
 
 VII. Strasser & Rhode, Glashiitte nr. Dresden. 
 
 Clock and Watch Works. 
 Exhibits : 
 
 1. Micrometer Gauge with short callipers, suitable for accu- 
 rately calibrating carbon filaments for incandescent lamps, glass- 
 tubes etc.; 
 
 2. Micrometer Gauge with long callipers, which may be con- 
 veniently used in mechanical work -shops and glass-blowing 
 establishments. 
 
W. Dieckmann, Celle. 157 
 
 No. 2805. 
 
 W. Dieckmann, Celle. (Hannover.) 
 
 Sculptor. 
 Geographical, astronomical and chiming art clock. 
 
 This clock rests upon a pedestal made of American walnut wood, 
 treated in the style of modern renaissance of the 16th century. The 
 clock and pedestal together have a height of 2.70 meter. The front 
 dial is made of ivory, ebony, rose wood and mother of pearl. The other 
 dials are made of enamel, the figures and hands of fire gold. Beside 
 the main dial the clock has on either side of the case 8 dials which 
 indicate the times of the following towns: 
 
 Left side: 
 
 Europe: Berlin, Stockholm, St. Petersburgh, Constantinople, 
 Vienna, Eome, Paris, London. 
 
 Right side: 
 
 North and South America: Washington, New York, 
 Philadelphia, Carracas, Buenos Ayres, Quito, Mexico, 
 San Francisco. 
 
 On the opposite side of the main dial the clock has a permanent 
 calender movement which indicates the day of the week, the day of the 
 month, the time difference between mean and actual solar time and the 
 phases of the moon. This movement effects also automatically the change 
 of day in leap years. 
 
 The clock work is actuated by a spring and requires winding once 
 in 8 days; It strikes the quarter and full hours. Every hour after the 
 striking of the full hour the clock sets a musical movement in motion 
 which plays a fresh piece every hour. 
 
 The clock and pedestal are decorated with 54 sculptured represent- 
 ations and ornamentations. 
 
 The clock is for sale. Intending purchasers are requested to commu- 
 nicate with Mr. Hirschmann, the representative at the Exhibition. 
 
158 G. Kromschroder, Osnabriick. C. Bube, Hannover. 
 
 No. 2808. 
 
 G. Kromschroder, Osnabriick. 
 
 Manufacturer of dry gasmeter with seemless diaphram. 
 
 BRANOHESj: 
 Wien III. Zwolle. 
 
 Erdbergerstr. 68. (Holland.) 
 
 No. 2809. 
 
 C. Bube, Hannover. 
 
 Maker of Linear Measures. 
 
 Falmk-Zeiuhen. 
 
 Mathematical, Drawing, Builder's and Folding Divided Eules of 
 all kinds. - - Steel measuring tapes, Measuring chains etc. 
 
 Speciality: Folding Rules with Patent Fixing Clamp, patented in 
 the U. S. A. and in all the principal European countries. 
 The works were established in 1854. 
 
 Awards : 
 
 Hannover 1859: Bronze Medal. 
 Moscow 1872: Larger Silver Medal* 
 Vienna 1873: Medal of Merit 
 Hannover 1878: First Prize. 
 
 Agents in the U.S.A.: 
 
 Keuffel & Esser Co., 
 265 State Street, Chicago, and 127 Fulton Street, New York. 
 
Imperial Physical and Technical Institute. 159 
 
 No. 2810. 
 
 Imperial Physical and Technical Institute. 
 Charlottenburg nr. Berlin. 
 
 I st Department: 25 Marchstr.j 
 II nd Department: 151 Berlinerstr. 
 
 The Imperial Physical and Technical Institute comprises two de- 
 partments. The work of the first or Physical Department consists in 
 such physical researches and measurements which are calculated to lead 
 to the solution of scientific problems of great general importance and 
 which envolve sacrifices exceeding the resources of private individuals 
 or schools. 
 
 The object of the second or Technical Department is twofold, viz 
 
 1. To carry out physical and technical investigations which may 
 from time to time be ordered by the Autorities or which may be cal- 
 culated to promote the manufacture of philosophical instruments or to 
 contribute to the growth of other branches of German industry; 
 
 2. To test and certify graduated instruments and standardizing 
 appliances, provided these do not more properly belong to the 
 Assize Department. 
 
 The following are the exhibits of the Institute: Samples of gra- 
 duated appliances admissible for attestation, thermometers,tuning forks etc. 
 accompanied by their respective certificates. - Samples of materials 
 adapted for fine mechanical and electro-technical art, standard screw 
 threads and tempering colour? insti uments * nd appliances, illustrations, 
 diagrams and publications. 
 
 A detailed description of the exhibits will be found in the Zeit- 
 schrift fur Instrumentenkunde, Berlin, Springer; New York, B. Wester- 
 mann & Co., 1893, 4th number. 
 
160 Hartmann & Braun, Bockenheim- Frankfort o. M. 
 
 No. 1349. 
 Group 123. 119. 
 
 Hartmann & Braun, 
 Bockenheim -Frankfort o/M. 
 
 Scientific Instruments and Electrical Apparatus. 
 
 (150 Employees and Steam power of 36 kilowatt) 
 
 Silver medal, Paris 1881. Gold medal, Turin 1884. 
 
 Silver medal, London 1885. Gold medal, Antwerp 1885. 
 
 This firm is exhibiting in a separate room situated at the 
 exit of the German Division on the Ground Floor of the Electri- 
 city Building. This room contains a fully equipped laboratory, in working 
 order, suitable for an electrical research laboratory, a central lighting 
 station or for an extensive electrical manufacturing concern ; also a collection 
 of measuring apparatus for workshop use, for electrical fitting and cable 
 laying, amperemeters and voltmeters, resistance apparatus, electrical 
 measuring instruments for continuous and alternating currents: finally, 
 a collection of electrical and magnetic instruments of precision. 
 
 In the centre of the room. 
 
 1. Appliances for measuring resistances of 0.01 to 11 million 
 ohms, consisting of a universal resistance bridge with plug connections, 
 reflecting galvanometer with reflecting magnet and reading telescope. 
 
 2. Apparatus for measuring current strengths and E. M. F.'s 
 by the compensation (Null) method, consisting of a Clark standard cell 
 and ballast resistance, resistance box for main and shunt circuits, a branch 
 resistance of 0.01 ohm, an aperiodical reflecting galvanometer with 
 Siemens' bell magnet and reading' telescope. 
 
Hartmann & Braun, Bockenheim- Frankfort o. M. 
 
 161 
 
 3. Apparatus for measuring high insulation resistances 
 
 consisting of an astatic cable galvanometer with Bruger's magnets, 
 several shunt resistances, a scale lamp for objective reading, a megohm 
 with 10 subdivisions as standard of comparison, a battery of dry accu- 
 mulators with universal pachy trope and switches. 
 
 4. Apparatus for measuring capacities ol cables, consisting 
 of a ballistic reflecting galvanometer with Weber's magnets, a reading 
 telescope, a condenser of one microfarad with subdivisions, together with 
 -charge and discharge keys. 
 
 The reflecting galvanometers of the preceding four groups are mounted 
 upon isolated brick piers, the optical reading appliances belonging to them are 
 placed upon adjustable Gauss stands. 
 
 Upon tables arranged along the walls. 
 
 5. Apparatus for measuring small resistances, in particular, 
 for testing the conductivities of materials, consisting of a resistance 
 bridge with key, amperemeter and sensitive galvanometer. Range from 
 O.00001 to 5 ohms. 
 
 The measurements are made on the principle of the Wheatstone bridge, 
 modified, however, in such a manner that by double reading the intermediate 
 resistances are eliminated. The result is obtained without extensive calculation 
 -by direct reading from the scale of the apparatus. By means of universal 
 clamps conductors of any section and also carbons may be placed in the circuit. 
 
 6. Apparatus for testing iron and steel with respect to magnetic 
 permeability and coercive properties, consisting of a standard electro- 
 magnet, a Lenard's bismuth spiral, a bridge for determining the strength 
 -of the magnetic field, a galvanometer constructed on Deprez's principle 
 -and an amperemeter. 
 
 11 
 
162 Hartmann & Braun, Bockenheim- Frankfort o. M. 
 
 7. Apparatus for determining the resistances of electrolytes 
 according to Kohlrausch, consisting of a KirchhofiMYheatstone bridge, 
 cylindrical form, an induction apparatus for generating alternating 
 currents, an unifilar suspension electro-dynamometer, a telephone, three 
 U-tubes with platinum electrodes and Arrhenius' resistance vessel. 
 
 8. Photometric apparatus, consisting of a large precision photo- 
 meter with Lummer-Brodhun's comparison prism, standard amylacetate 
 lamp, universal incandescent lamp stand, revolving mirror for determining 
 the illuminating power of arc lights at various angles of emission, volt- 
 meter and wattmeter for measuring E. M. F's and energy expended in 
 incandescent lamps. 
 
 By means of an intransparent curtain a dark room can be expeditiously 
 improvised. 
 
 Small Appliances. 
 
 9. Resistance Bridge for determining the resistances of solid 
 conductors, e. g. iusulated wire wound on a bobbin, with aperiodieal 
 needle galvanometer. Eange from 0.1 to 10000 ohms, reading directly 
 without calculation. 
 
 10. Small universal resistance bridge-, according to Kohlrausch, 
 for determining resistances of solid conductors and electrolytes, e. g. the 
 internal resistance of cells by means of alternating currents, generated 
 by means of an induction coil supplied with the apparatus. A telephone 
 is used for measuring in place of the galvanometer. Range from 0.01 
 to 1000 ohms, direct reading. 
 
 The two preceding appliances are specially adapted for workshop use. 
 
 11. Wheatstone-Kirchhoff Bridge with measuring wire of 1 meter 
 length, which may be extended for very accurate measurements by 
 additional stretched wire resistances. The meter wire is calibrated by 
 means of a second contact slider, which renders the apparatus also 
 available as a Thomson double bridge. Precision resistance box or single 
 standard resistance coils serve as comparison resistances. 
 
 12. Differential Galvanometer with index for comparing any 
 resistances; the latter will be found among the exhibits in the shape of 
 a decade crank resistance box and a series plug resistance box. 
 
Hartmann & Braun, Bockenheim- Frankfort o. M. 
 
 163 
 
 13. Differential Galvanometer with bobbins, wound with 
 resistances in the ratio of 1 : 20. By means of this instrument the 
 resistance of an incandescent carbon filament may easily be found by 
 Voller's method. 
 
 14. Apparatus for determining small resistances according to 
 Kirchhoff's differential shunt method, consisting of a standard resistance 
 of 0.01 ohm, two precision resistance boxes and a differential galvano- 
 meter, the latter modified according to Deprez. 
 
 15. Nippoldt's Testing Apparatus for Lightning Conductors, 
 consisting of Wheatstone bridge reading directly, contained in the casing 
 of a telephone, a small induction co'il together with cells for generating 
 alternating currents, or if desired a simple galvanometer, the whole 
 in a sling case; also a folding earth plate. 
 
 . The resistance due to the passage from the lightning conductor to the 
 earth plates has, on account of the polarization taking place at the plates, like 
 the resistances of electrolytes, to be measured by means of alternating currents, 
 hence a telephone is substituted for a galvanometer. It is useless to measure 
 the resistances of the metallic conductors, as these can only be examined by 
 ocular inspection. 
 
 16. Tangent Galvanometer for currents and E. M. F.'s, 
 with Kohlrausch water voltameter for calibrating by volume of ga(s ge- 
 nerated, and a comparison amperemeter. 
 
 The method of calibration by means of the Kohlrausch water voltameter 
 is extremely simple and does not involve the use of an analytical balance, as is 
 the case with the silver or copper voltameter. The tangent galvanometer has 
 a range of 3 miUiamperes to 25 amperes; with the aid of shunts or additional 
 resistances its range may be extended considerably. 
 
 11* 
 
164 
 
 Hartmann & Bratm, Bockenheim- Frankfort o. M. 
 
 17. Silver Voltameter and Copper Voltameter for calibrating 
 industrial galvanometers, the former for a current of 0.25 amp., the 
 latter for currents up to 5 amp. Also Kohlrausch's Water Voltameter. 
 
 Analytical balance for determining the weight of silver or copper 
 deposited by the voltameters. 
 
 18. Direct Reading Aperiodical Torsion Galvanometer, 
 ranging from 1 to 100-fold. Various models 
 
 for current strengths within the limits of 1 milliampere 
 and 10 amp.; 
 
 for E. M. F.'s within the limits of 0.01 and 1000 volts; 
 also combined in one instrument with shunts and addi- 
 tional resistances for 0.1 to 18 amp. and 0.1 to 180 volts. 
 These torsion galvanometers are constructed on the lines of Deprez's 
 galvanometer, but embody a series of very important improvements, the main 
 object of which are to maintain a constant homogeneous magnetic field, to shield 
 the instrument from the influence of the extraneous circuit and to add to the 
 portability of the instrument. 
 
 19. 
 
 19. Torsion Electro dynamometer for continuous and alternating 
 currents. Various models, for use 
 
 as amperemeter for currents up to 50 amp., 
 as voltmeter for E. M. F.'s up to 180 volts, 
 as wattmeter for energy up to 120 voltamp. 
 
 The indications of these instruments are based upon the movements 
 produced by a solenoid acting upon a double rotating solenoid with similar outer 
 and inner poles: NS SN. 
 
 The convenience of direct reading by means of a scale having nearly 
 proportional divisions, the range from 1 to 100 -fold measurement, the damping 
 arrangement, in particular however the absence of magnets or iron render these 
 instruments eminently suitable for calibrating other instruments. 
 
Hartmann & Bratin, Bockenheim- Frankfort o. M. 
 
 165 
 
 Apparatus 
 for measuring Temperatures by Electrical Instruments. 
 
 20. Braun's Pyrometer for temperatures up to 1000 and up to 
 1500 C, based upon the variation of the resistance of a platinum wire 
 wound so as to obviate self-induction inside a non-combustible box and 
 forming one branch of a "Wheatstone bridge. The sensibility is so great 
 that with the highest temperatures an increase or decrease of but a few 
 degrees is rendered apparent. The absolute accuracy is extremely great, 
 the instrument being standardized by numerous comparisons with a 
 
 porcelain air thermometer. 
 
 
 
 The necessary manipulations are extremely simple and imply no previous 
 experience. The temperatures are directly read from a scale on the apparatus; 
 the latter may be set up at a distance of several meters from the oven. This 
 pyrometer forms therefore a most suitable controlling instrument in metallurgical 
 and ceramic operations. 
 
 21. Tele-thermometer, similar in prin- 
 ciple to the pyrometer but limited to tempera- 
 tures between 30 and 300 C. Within these 
 limits the scale may be adjusted as required. 
 
 The manipulation is still simpler than that 
 of the pyrometer. The telethermometer is princi- 
 pally adapted for regulating the temperature in 
 schools and public buildings from a central heating 
 station, for conservatories, or inaccessible spaces, 
 e. g. malt-kilns, drying rooms, baking ovens etc. 
 
 Measuring Apparatus according to Kohlrausch. 
 
 In the case placed at the right hand side of the entrance. 
 
 22. Wheatstone - Kirchhoff Bridge. The resistance wire which 
 is 3 meters long, is wound upon a cylinder of white marble, there being 
 10 convolutions; the permanent connections are ensured by brushes; the 
 sliding contact is made by a small wheel. The comparison resistances 
 of 1, 10, 100, 1000 ohms and the resistances which are to be measured 
 are interchangeable by means of plug connections. Eminently suitable 
 for exact measurements. 
 
166 
 
 Hart-maim & Braun, Bockenheim- Frankfort o. M. 
 
 23. Unifilar Suspension Electro-dynamometer for small currents 
 with mirror reading. The current is led to the movable bobbin by the 
 suspension wire and a platinum coil, acting as a damper, dipped into 
 dilute sulphuric acid. 
 
 24. Portable Differential Galvanometer with mirror reading. 
 Provided with a small magnetic steel mirror suspended within the oval 
 multiplier. The amount of damping may be regulated by means of a 
 copper sliding piece. The sensibility is rendered variable by various 
 thicknesses of the duplex winding and by a controlling astatizing magnet. 
 Without astatization and with a resistance of 50 ohms a deflection of 
 1 mm reads 0.0000004 amp. at I meter distance of scale. 
 
 25. Absolute Tangent Galvanometer. The current passes 
 through a copper ring which can be accurately measured. All unneces- 
 sary metal parts are avoided. The reflecting magnetometer, which is 
 free from metal, may be removed and replaced by a needle. 
 
 26. Portable Bifilar Suspension Variometer for Terrestrial 
 Magnetism. Tubular strongly damped magnet suspended by two fine 
 wires placed a short distance apart. The constants are found by means 
 of a torsion circle provided with vernier and micrometer adjustment. 
 Expeditiously set up. Changes of position controlled by stationary 
 
 mirror. 
 
 27. Intensity Variometer for Terrestrial Magnetism. The 
 magnetic steel mirror is, by means of 4 small deflection magnets, placed 
 at right angles to the meridian, so as to neutralize the influence of 
 variation of declination. The sensibility may be regulated to any de- 
 
Hartmaim & Braun, Bockenheim- Frankfort o. M. 167 
 
 sired degree. A small reading telescope is directly attached to the in- 
 strument. Degree of precision: 1 : 10000. 
 
 28. Simple Local Variometer for measuring local changes of 
 the horizontal intensity. Only one instead of four deflection magnets; 
 a simple needle instead of a magnetic mirror; otherwise similar to 
 27, but of greater portability. Degree of precision: 1 : 1000. 
 
 29. Absolute Bifilar Suspension Magnetometer. By exact 
 measurement of the relatively great distance of 12 mm between the 
 wires, the deflections due to the reversal of the tubular magnet give 
 the product of the magnetism of the bar magnet and the terrestrial 
 magnetism in absolute measure. Simultaneous observation made with 
 a nnin'lar suspension magnetometer gives the intensity of the terrestrial 
 magnetism in absolute measure. The advantages of the method consist 
 in rendering the measurement of time and of the influence of tempe- 
 rature dispensable. 
 
 30. Absolute Bifilar Suspension Galvanometer. The magnet 
 is replaced by a wire ring of many convolutions which may be measured 
 exactly. The deflections of this ring due to a current represent the 
 product of strength of current, area of circuit and terrestrial magnetism. 
 This instrument may be used for absolute measurements of currents or 
 terrestrial magnetism by using it in combination with an absolute 
 tangent galvanometer or a single suspension magnetometer. 
 
 31. Spring Galvanometer. A tube of thin sheet iron sides is sus- 
 pended by a torsionless spiral of many convolutions and is drawn into 
 & solenoid by the current. The amount of the attraction is seen from 
 a scale divided, in amperes. The indications are aperiodical and in- 
 dependent of strong extraneous currents. The instruments are adapted 
 for currents up to 3000 amp. 
 
168 Hartmann & Braun, Bockenheim- Frankfort o. M. 
 
 Standards made according to the standards in 
 
 possession of the Imperial Physical and Technical Institute, 
 
 Berlin - Charlottenburg. 
 
 In the case at the left hand side entrance. 
 
 32. Clark's Standard Cell. The mercury electrode formed by 
 amalgamated platinum, is sealed in a porous pot together with the mer- 
 curous sulphate paste, by which means the cell is rendered portable. 
 A thermometer dipping into the cell has its scale outside. The glass 
 is protected by a metal casing. E. M. F. = 1.438 (15 0.) 
 
 33. Standard Resistances, of 0.1, 1, 10 etc. up to 10000- 
 ohms, made of manganine or constantan i. e. a material the coefficient 
 of temperature of which may be neglected, with nickel plated electrodes 
 for immersion in mercury cups. 
 
 The resistance coils are accurately calibrated and soldered with silver to 
 the electrodes contained in perforated metal cases. Paraffine baths may therefore 
 be used for measurements at constant temperatures. 
 
 34. Standard Resistances, 0.01, 0.001 and 0.0001 ohm, which 
 may also be used as shunts for exact current measurements; made in a 
 similar manner to those described in 33, excepting, that thin laminae 
 
 are substituted for the 
 wires; fitted, apart of 
 the electrodes, with 
 two binding screws, 
 which branch off at 
 the exact terminals of 
 84< tT 11 i( IBIMHHP 8 * ^3Fr H\ i! 1 the resistances. 
 
 0.001 and 0.0001 are- 
 contained in entirely 
 closed metal cases fitted 
 with cooling worm and 
 stirrers for parafh'ne 
 filling. 
 
 35. Paraffine baths with nickel plated double mercury cups r 
 suitable for 2 to 4 standard resistances, with stirring apparatus driven 
 by a tiny electromotor. 
 
 36. Small Compensation Apparatus containing a Clark stan- 
 dard cell and high ballast resistances (100 000 ohms), a commutator 
 switch and a very accurately adjusted resistance box also of 100 OOO 1 
 ohms; the latter is adjustable up to 10 000 ohms by plugs and cranks r 
 by means of which the resistances which are to be placed in the com- 
 pensation circuit may be found. Very intelligible and compact arrange- 
 ment and convenient manipulation. 
 
 37. Large Compensation Apparatus. Similarly arranged but 
 with entire adjustable resistance box and having besides an equalization 
 resistance, whereby the correction of the temperature in the Clark 
 cell is introduced into the apparatus which thus becomes direct reading. 
 
Hnrtmarm & Braun. Bockenheim - Frankfort o. M. 
 
 The remainder of the instruments constructed by this firm. 
 
 In the centre case. 
 
 38. Portable Telescope Galvanometer. Bell magnet in very 
 narrow copper piece effecting aperiodical damping; clamping for safe trans- 
 port; expeditious adjustment by means of circular level. Multipliers wound 
 with double convolutions, movable and interchangeable. Telescope attached 
 to instrument with scale placed at 25 cm distance. Suitable for all 
 galvanometric measurements occurring in workshop, laboratory and out- 
 door work. 
 
 Sensitiveness without astatization at 100 ohms: 1 mm deflection 
 = 0.0000009 amp.; with astatization at 4000 ohms: 1 mm deflection 
 = 0.00000009 amp. 
 
 39. Suspended Coil Galvanometer. A broad and homo- 
 genious magnetic field is obtained by a number of powerful magnets 
 having common poles. Movable bobbin suspended by quartz thread, with 
 safe clamping for transport. The current is admitted by extremely thin 
 
 silver laminae. The oscillations are aperiodical also when no current is 
 passing and when high resistances are placed in the circuit. With index 
 and mirror reading. Also arranged for use as a differential galvanometer. 
 Sensitiveness at 10 ohms: 1 degree of index = 0.000005 amp., 
 or with mirror reading: 1 mm at 1 meter distance of scale = 
 0.000 000 1 amp. 
 
 40. Micro-Galvanometer, Rosenthal's principle, with )( shaped 
 astatic magnetic system, the 4 poles of which dip into 4 small solenoids. 
 Great sensibility combined with small consumption of wire. Particularly 
 suitable for physiological and thermo-electric currents. 
 
 Sensitiveness at 200 ohms: 1 mm*) = 0.000000006 amp. 
 
 41. Astatic Reflecting Galvanometer with Nobili's magnetic 
 system inserted from the side and closely surrounded by the multipliers. 
 Adjustment of damping by means of various copper shells. 
 
 Sensitiveness at 10 ohms and 10 seconds duration of oscillations: 
 1 'mm = 0.000 000 15 amp. 
 
170 
 
 Hartmann & Braun, Bockenheim- Frankfort o. M. 
 
 42. Ballistic Reflecting Galvanometer, according- to Weber's 
 arrangement, with short tube magnets and interchangeable multiplier. 
 Adjustable duration of oscillations : 15 seconds. 
 
 Sensitiveness at 50 ohms: 1 mm*) = 0.00000002 amp. 
 
 43. Large dead beat Reflecting Galvanometer. Eigid struc- 
 ture; bell magnet in lentiform copper damping shell, may be interchang- 
 ed for a ring magnet; double wound multiplier with rack and pinion 
 movement; astatization by means of a ring of soft iron. In this instru- 
 ment are combined the special features of the types of Siemens, Wiede- 
 mann, du Bois-Eeymond, Becquerel and Braun. 
 
 Sensitiveness without astatization at 400 ohms: 1 mm*) 
 0.00000007 amp. 
 
 44. Simple dead beat Reflecting Galvanometer, similar in 
 construction to 43, but a little smaller and simpler. Multiplier arranged 
 to be moved by hand. Suspension by quartz thread. 
 
 Sensitiveness: nearly the same as with 43. 
 
 45. Astatic Aperiodical Reflecting Galvanometer. Bruger 
 magnets consisting of the two coupled halves of a vertically suspended 
 hollow cylinder, which combine the advantage of diminished inertia with 
 considerable magnetic momentum and high degree of astatization. 
 Suspension by quartz thread. Damping adjustable within wide limits. 
 Conveniently set up; fitted with small telescope, 50 cm distance, directly 
 attached to instrument, so as to render the instrument available for out- 
 door use. 
 
 Sensitiveness at 5000 ohms and 15 seconds duration of oscillations: 
 1 mm*) = 0.0000000025 amp.. 
 
 *) With reflecting galvanometers the sensitiveness refers always to a 
 deflection of 1 mm at a distance of scale of 1 meter. 
 
Hartinann & Braun. Bockenheim- Frankfort o. M. 
 
 171 
 
 46. Reading Telescopes for observation with reflecting instruments. 
 3 different sizes with bright field, objectives of 30, 40, 55 mm aperture 
 and euroscopic micrometer oculars; micrometer adjustment in either 
 plane and vertical rack and pinion movement. Rigid structure*, entire 
 absence of iron. 
 
 47. Simple Reading Telescopes of 27 mm aperture; with con- 
 venient scale support, for use in a horizontal and vertical position. Two 
 different patterns; one to be adjusted by hand, the other one by rack 
 and pinion. 
 
 48. Lamp Stand and Scale for use with reflecting instruments, 
 w r ith petroleum burner, Argand burner or incandescent lamp. Scale 
 arranged to be observed from the front or from the back. 
 
 49. Scales for mirror reading; very accurately divided in 
 lengths of 40. 60, 80, 100 120 cm, of wood T section, with narrow 
 paper strips, also transparent celluloid mounted in wood- lath; also 
 of plate glass, transparent or greyed, and of milk glass, the latter kind 
 being specially adapted for telescopic measurements. 
 
 4S. 
 
 44. 
 
 50. Box Galvanometer, with bell magnet suspended by silk 
 fiber or quartz, in powerful damper with stopping spring; intelligible 
 arrangement; made to revolve on metal foot; with high or low resistance. 
 
 Sensitiveness: at 5 ohms: 1 = 0.00005 amp. 
 
 51. Aperiodical Differential Galvanometer with index reading; 
 very portable. Double wound multipliers, movable and interchangeable; 
 sensibility variable within wide limits. When the astatization is intro- 
 duced, which can easily be done, the sensitiveness at 100 ohms is: 
 If = 0.000 002 amp. 
 
 52. Vertical Galvanometer, Deprez's principle; an exceedingly 
 handy instrument. 
 
 Sensitiveness: 1 = 0.0001 amp. ; 
 
172 
 
 Hartmann & Braun, Bockenheim- Frankfort o. M. 
 
 Rheostats for scientific exact measurements 
 
 very accurately calibrated, 
 of constantan or manganine wire, wound so as to obviate self-induction. 
 
 53. Series of 0.1, 0.2, 0.3, 0.4, 1, 2, 8, 4, 10, 20 etc. to 4000 
 ohms, i. e. in combinations of upwards of 11 111.1 ohms, with plug 
 connections. Also in 
 
 54. Decades of 4 x 2 + 1 4- 1 or 10 x [0.1, 1, 10, 100, 
 1000, 10 000, 100 000] ohms, with plug connections. Also in the form of 
 
 55. Branching Rheostats, with pairs of 1, 10, 100, 1000 and 
 10 000 ohms. Also in the form of 
 
 56. Resistance Bridges composed of series or decade resistance 
 boxes with branch resistances. Finally,? injthe form of 
 
 57. Shunts and Addition Rheostats, for diminishing the sensi- 
 tiveness or extending 1 the range of galvanometers. 
 
 Rheostats for industrial exact measurements. 
 
 58. Single Resistances of 1, 10, 100 up to 10000 ohms. 
 
 59. Series of 1, 2, 3, 4; 10, 20, 30, 40; 100, 200 etc.; giving a 
 total maximum of 11 110 ohms, with plug connections. Also in 
 
 60. Decades of 10 x [1, 10, 100, 1000] ohms with crank changer. 
 Finally, in the form of 
 
 61. Resistance Bridges, combined decade and branch resistances. 
 
 62. Portable Resistance Bridge, with galvanometer, of 0,01 
 to 1 million ohms, for comparing E. M. F.'s of single cells, con- 
 sisting of 4 decades, 3 pairs of branch resistances, pole reverser, switch 
 and with key; all parts fitted with crank manual; in case fitted with lock. 
 
 All resistances are joined by separate conductors to the connecting pieces, 
 there being no common conductors. By means of terminal plugs which are to 
 be inserted at the side any one of the resistances may be branched off. 
 
Hartmann & Braun, Bockenheim- Frankfort o. M. 
 
 173 
 
 Electrical Measuring Instruments for School Purposes. 
 
 In the following instruments particular attention has been paid to 
 simplicity and intelligible arrangement of the parts and care has been 
 taken to render the movements of the pointers and the divisions on the 
 dial distinctly visible from a distance of 10 meters. 
 
 63. Lecture Galvanometer with bell magnet, powerful damper, 
 with pointer; interchangeable multipliers; also for use as a differential 
 galvanometer. The pointer magnet may be replaced by a reflecting 
 magnet. The galvanometer may thus be used as a reflecting galvano- 
 meter for projection on the screen or for telescopic reading. 
 
 64. Simple Lecture Galvanometer, with 2 bar magnets, one of 
 these, the astatizing magnet, being detachable. The whole instrument 
 can be taken to pieces. 
 
 65. Resistance Bridge with stretched measuring wire of 1 meter 
 length, divided in half decimeters for the audience and in millimeters for 
 the purposes of the lecturer. 
 
 66. Open Wire Coils, wound 
 so as to obviate self-induction, of 1 
 and 10 ohms, forming comparison 
 resistances. 
 
 88. 
 
 67. Lecture Voltmeter. Iron core drawn into solenoid. Coun- 
 teracting spring. The rectilinear movement is by means of a lever 
 transmitted to the centre of the pointer. Eange 0.5 to 3 volts. Also sui- 
 table for measuring the voltage of single cells. By means of an additi- 
 onal resistance the range may be increased 10 times. 
 
 68. Lecture Amperemeter, similar construction, range 0.2 to 2 
 amperes, with shunt up to 10 amperes. 
 
 69. Induction Apparatus. The secondary coil is detachable and 
 the iron core may be replaced by a magnet. The apparatus is adapted 
 for Faraday's experiments on induction. 
 
 70. Telephone having all its parts exposed to view, forming an 
 alternating current galvanometer for measurement of fluid resistances, 
 -e. g. the internal resistances of cells in connection with bridge 65 and 
 induction apparatus 69. 
 
174 
 
 Hartmann & Baum, Bockenheim -Frankfort o. M. 
 
 On the Platform in the centre of the room. 
 
 71. Large Electromagnet with vertical bobbins, fitted with all 
 appliances for Faraday's experiments, also with 
 
 72. Waltenhofen's Induction Pendulum and 
 
 73. Lenard's Bismuth Spiral for measuring magnetic fields. 
 
 74. Weber's Earth Inductor for determining terrestrial magnetic 
 inclination. A. magnetometer supplied with the inductor for adjusting 
 purposes renders it suitable for a tangent galvanometer. 
 
 75. Astatic Oscillation Galvanometer according to Weber, for 
 observing inductive impulses by the earth inductor. Adjustable damping. 
 
 76. Magnetometer according to Gauss and Weber, for deter- 
 mining the terrestrial magnetic declination and the horizontal intensity 
 by observations of oscillation and deflection. 
 
 77. Reflecting Electrometer for measuring electro-static po- 
 tential differences. The peculiar arrangement and shape of the vane 
 renders the deflections proportional within wide limits. Ranging from 
 1 to 500 fold between 1 and 50000 volts. 
 
 Industrial Direct Reading Instruments for large currents, 
 
 for E. J\f. F. 3 Sy Intensity, 
 Insulation resistances., Energy expended. 
 
 Displayed along the walls. 
 
 78. Voltmeter and Amperemeter for continuous currents. 
 Circular cases, two sizes. Attraction of core of rolled sheet iron into 
 solenoid; torsion counter spring (compensation of temperature by double 
 spiral). Transformation of reciprocal in circular motion by means of 
 lever with jewelled pivots. The peculiar form of the iron core admits 
 of the form of the dial being varied at will. 
 
 Range from 1 to 20-fold reading, numerous models for all currents 
 up to 3000 amp. 
 
Hartmann & Braun, Bockenheim- Frankfort o. M. 
 
 175 
 
 79. Voltmeter and Amperemeter for continuous and alter- 
 nating currents. Circular case. Two different sizes. Reciprocal action 
 within a solenoid (attraction or repulsion) of two or more extremely 
 light segments of a cylinder shell of soft iron. Index on aluminium 
 center with jewelled steel points. 
 
 In spite of the presence of iron these instruments are available 
 both for continuous and alternating currents, with the same calibration, 
 irrespective of the rapidity of pole reversion. Range from 1 to 10-fold. 
 
 Made as a voltmeter in 15 differently calibrated forms, from 0.5 
 to 3000 volts. 
 
 Made as an amperemeter, in, 16 differently calibrated, forms, from 
 0.5 to 3000 amp. 
 
 91. 
 
 80. Double Solenoid Voltmeter and Amperemeter for conti- 
 nuous and alternating currents. 
 
 An annular iron core of extremely small polar distance is excentri- 
 cally pivoted between two conaxial solenoids; the current tends to place 
 the core conaxial with respect to the solenoids. 
 
 81. Hot wire Voltmeter and Amperemeter, for continuous 
 and alternating currents; with small consumption of energy. In the case of 
 the voltmeters the bend of a short, very thin wire, through which the 
 current passes, is heated and the amount of the expansion is transmitted 
 by a peculiar device to the axle of the pointer. These voltmeters are 
 by means of suitable introduction of resistances calibrated to indicate 
 from 3 to 3000 volts. 
 
 In the case of amperemeters a shunt is added to the heating wire 
 or a heating wire of suitable thickness is made to heat a metal tube 
 fixed at one end and the expansion of the latter is transmitted by means 
 of a contact lever to the center of the index. 
 
176 
 
 Hartmann & Braun, Bockenheim- Frankfort o. M. 
 
 Both instruments are provided with arrangements for compensating 
 influences of external temperature. 
 
 82. Electrostatic Voltmeter for high voltage, in circular case. 
 By the peculiar shape and arrangement of the working parts the 
 
 intervals of the scale are rendered nearly proportional. Range from 
 1 to 10-fold, between 100 and 50000 volts. 
 
 83. Aperiodical Voltmeter and Amperemeter for continuous 
 currents on Deprez's principle. In circular case. 
 
 84. Differential Voltmeter for controlling the voltage in the 
 two circuits of three wire systems. 
 
 85. Universal Voltmeter for controlling the voltage in central 
 electric light installations, for continuous and also for alternating currents 
 with scale divisions visible at a great distance; scale embracing the 
 range of voltage of a particular plant. Two sizes of 50 and 35 centi- 
 meters diameter. 
 
 87. 
 
 86. Contact Voltmeter with minimum and -maximum efficiency, 
 for giving visible and audible signals or for actuating automatic voltage 
 regulators and cell switches, in the latter case with the aid of inter- 
 mediate Relais. 
 
 87. Signalling Voltmeters with direct reading of the normal 
 voltage. Incandescence of a green lamp signifies that the voltage has 
 become too low, that of a red lamp that it has risen too high. An 
 alarm bell is sounded at the same time. 
 
 88. Voltmeter for special purposes, e. g. for testing accumu- 
 lators, for electro-plating, for ships, railways and tram-cars, in various 
 forms according to the special purpose. 
 
Hartmann & Braun, Bockenheim- Frankfort o. M. 
 
 177 
 
 89. Registering Voltmeters and Amperemeters, on the prin- 
 ciple of Kohlrausch's spring galvanometer, which is particularly adapted 
 for this purpose on account of its relatively powerful action, the recti- 
 linear movement of its iron core suspended by a torsionless spring and 
 its perfect damping. With 24 hours and 8 day clock work for the re- 
 gistering drum. 
 
 90. Wattmeter for direct reading. In circular case. External 
 shunt connection as with the voltmeter and amperemeter; the system is 
 similar to No. 19, but arranged vertically and fitted with horizontal axis 
 pivoted between two points. For purrents up to 30 amperes and for 
 voltages up to 150 volts. With extra shunts and additional resistances 
 for several hundred amperes and several thousand volts. 
 
 91. Ohmmeter in circular case for per- 
 manent connection with the circuit, for taking 
 at any time direct readings of the resistances 
 of insulations in ohms. By means of a com- 
 mutator either the positive or the negative pole 
 may be examined with respect to earth con- 
 nection. The instrument can be made for an}' 
 constant voltage. 
 
 92. New Ohmmeter for taking direct 
 readings of resistances. Astatic magnetic system 
 with differential multiplier, so arranged that the 
 indications of the instrument are affected neither 
 by terrestrial magnetism nor by the magnetic 
 momentum of the needle nor by the voltage 
 of the battery. Range from single to hundredfold 
 reading. 
 
 93. New Volt-Coulombmeter. The current which is to be 
 registered deflects the movable system of a wattmeter; a spring supplies 
 the counterforce and is drawn out at short intervals by a very simple 
 clockwork actuated by the current. The travel of the spring is trans- 
 mitted to a registering set of wheels provided with electro-magnetic 
 coupling which becomes disconnected whenever the strength of the current 
 and the tension of the spring are in equilibrium. This play is repeated 
 every minute. Range from single to 200-fold. 
 
 94. Motor-Coulombmeter. By a peculiar arrangement the velo- 
 city of this motor, which is provided with electrical damping, is rendered 
 proportional to the current. By a special device absolutely certain starting 
 is ensured even with the weakest current. An automatic switch for the 
 
 12 
 
178 Hartmann & Braun. Bockenheim- Frankfort o. M. 
 
 armature wire prevents the motor from consuming any current except 
 when in motion. 
 
 95. Automatic Cut-outs for a certain maximum or minimum. 
 Efficient within 3%. 
 
 96. Automatic voltage Regulator. The sliding contact which 
 serves for connecting and disconnecting resistances is moved by a screw 
 in a straight line. The screw is coupled to a small electro-motor. The 
 latter takes its current in either direction through a contact voltmeter. 
 
 . 97. Automatic Switch for regulating the voltage by connecting 
 and disconnecting accumulators w : ith the circuit. Similar in construction 
 to No. 96. 
 
 98. Differential Arc Lamps with stationary luminous point, 
 A steady uniform light is obtained by the introduction of a clock work 
 which retards the movement of the carbons. Low structure, various 
 decorative designs, to burn from 5 to 15 hours, for currents from 1 to 15 amp. 
 
 96 and 97. 
 
 99. Small Electromotors of Vao > Vis and Vs HP ' wound as 
 series motors, and of l /4 ,' l /2 and * HP wourid as shunt motors. 
 The speed of the former varies according to the load, the latter run at 
 almost constant velocities. Both types are very efficient and well built. 
 
 100. Portable dynamo -machine for blasting; in wood case 
 with leather strap. It generates at a speed of about 3 rotations of the 
 crank per second 0.85 amp. and 75 volts (efficiency of 65 watts). Total 
 weight 10.5 kilos. The igniting electrodes consist of thin platinum wires 
 embedded in the cartridge. 
 
 Portable measuring appliances for use in the installation 
 of electrical plants. 
 
 Exhibited at the entrance of the Exhibition room. 
 
 101. Portable Measuring Apparatus for Cable Laying. Two- 
 wheeled firmly built truck fitted with resistance bridge for usual resistances, 
 an apparatus for testing insulation resistances by the method of 
 deflection, with a telescope galvanometer. Underneath a space is 
 provided for a stand upon which the galvanometer may be placed. By 
 
179 
 
 102. 
 
180 Hartmann & Braun, Bockenheim- Frankfort o. M. 
 
 I 
 
 means of a cloth folded upon the truck a tent can speedily be pitched 
 for the protection of the galvanometer and other instruments. A mea- 
 suring battery of 100 dry accumulators, with pachytrope for selecting 
 various voltages, and a controlling voltmeter and amperemeter complete 
 the apparatus. 
 
 102. Portable Apparatus for measuring the resistances of 
 cable insulations, consisting of a telescopic galvanometer with 3 shunts, 
 comparison resistance, a batterj^ of 100 cells with key; in oak trunk with 
 folding feet by means of which the trunk may be converted into a stand. 
 Range up to 500 megohms. 
 
 103. Similar Apparatus with simple needle galvanometer and 
 50 cells. Modification of the method of direct deflection, independent 
 of the voltage of the current generator. The results are found nearly 
 without calculation by a curve supplied with the apparatus. Range up 
 to 10 megohms. Weight 14 kilos. 
 
 104. Ohmmeter, also in oak case fitted with folding legs, con- 
 taining 50 cells. Direct reading of the required resistance of the 
 insulation within the limits of 1000 and 1 000 000 ohms. Weight 14 kilos. 
 
 105. Insulation tester for the examination of domestic installation 
 consisting of an induction coil which is made to act by continuous cur- 
 rent either upon a galvanometer of 100000 ohms resistance or by alter- 
 nating current upon a sounding apparatus with resistances up to 
 30000 ohms. 
 
 106. Portable Bridge with direct reading for resistances of 
 solids and electrolytes, e. g. for measuring the internal resistance of 
 cells or for testing earth connections of lightning conductors. Galvano- 
 meter, easily set up. Measuring telephone and cells. All in oak case. 
 Weight 11 kilo (vid. No. 10). 
 
 107. Portable Voltmeter and Amperemeter, mounted on tripod 
 or fitted in wood box with handle. The voltmeters intended for fitters 
 are so arranged that by means of a crank changer single portions of 
 the winding may be coupled in multiple arc or in series. The instru- 
 ments are accordingly provided with two scales, the range of one forming 
 the continuation of that of the other. The voltage may thus be mea- 
 sured within very wide limits. 
 
 108. Simple Incandescent Lamp Photometer, constructed on 
 Foucault's principle in such a manner that the candle power of the lamps 
 may be compared without dark room. Either a paraffine candle or a 
 standard incandescent lamp may be used as a standard of comparison. 
 The ratio of intensity may be read directly by a scale with range from 
 single to 10 fold reading. The apparatus is very light being only 1 meter 
 long. It may also be used for outdoor determination of the luminosity 
 of arc lamps. 
 
R. Fuess, Steglitz. 181 
 
 R. Fuess, 
 Steglitz nr. Berlin, 
 
 Diintherstrasse 2/8. 
 (Formerly J. G. Greiner jun. & Geissler.) 
 
 The exhibits are shown in the German University Exhibition. 
 
 I. Mineralogical Division. 
 
 41 Photographs of the principal instruments used in mineralogical 
 research; 3 sets in gilt frames. 
 
 1 large Microscope, Model No. 1. 
 
 Accessories and small auxiliary apparatus adjusted for micro- 
 scope No. 1, mahogany case. 
 
 1 Microscope, Model No. 3. 
 
 1 Microscope, 5. 
 
 1 Adams's Polarizing Apparatus, with goniometer for mea- 
 suring optical axes. 
 
 1 Klein's Reflecting Goniometer. 
 
 1 Universal Heliostat. 
 
 1 Case with set of thin rock sections. 
 
 II. Meteorological Division. 
 
 1 Sprung's and Fuess's Barograph. 
 
 1 Sprung's and Fuess's Anemograph with electrical registering 
 apparatus. 
 
 1 Sprung's and Fuess's Pluviometer, with electrical registering 
 apparatus. 
 
 1 Aspirating Psychrometer according to Prof. Assmann. 
 (Complete equipment for travellers in tropical climates.) 
 
 1 Aspirator for Psychrometers. 
 
 III. Meteorological Instruments for Explorers. 
 
 1 Fortin Barometer for measuring altitudes. 
 1 Hypsometer ., 
 
 1 Assmann's small Aspirator Psychrometer, 
 1 Sling-Thermometer, 
 
182 R. Fuess, Steglitz. ' 
 
 IT. Hygienic Division. 
 
 1 Anemometer for examining ventilations. 
 
 1 Anemometer with crossed bowls. Smallest model. 
 
 1 Koppe's Hair-Hygrometer. 
 
 1 Maximum and Minimum Thermometer. 
 
 V. Architectural Division of the Prussian Ministry of Public Works. 
 
 1 Registering water mark designed by Seibt and Fuess. 
 1 Water mark with divisions and figures on china. 
 10 Photographs of the principal instruments for registering water 
 marks designed by Seibt and Fuess, in frame. 
 
 (All information respecting these instruments may be obtained from 
 Mr. Winter, mechanician in the German University Exhibition. 
 
INDEX. 
 
 Alcoholometers: Schultze 92. 
 Anemometers: Fuess 181. 
 Aneroid-Barometers: Bohne 11. - 
 
 Lufft 47. Moeller 51. 
 Astronomical Instruments and 
 
 Appliances: Merz 49. - - Riefler 
 
 61. Steinheil Sohne 103. Tes- 
 
 dorpf 124. 
 
 Balances: Betting 11. Hasemann 
 
 17. Bunge (A. T Herzberg) 21. - 
 
 Staudinger & Co. 99. 
 Barometers, mercurial: Bock 14. 
 - Kiichler & SOhne 151. - - Alt, 
 
 Eberhardt & Jaeger 151. Greiner 
 
 152. Fuess 181. 
 
 Calculating Machines: Burck- 
 
 hardt 15. 
 
 Clocks: Riefler 61. Dieckmann 157. 
 Colorimeters: Krtiss 42. 
 
 Didactical Purposes, Apparatus 
 for: Kohl 35. Gebhardt 147. 
 
 Drawing Instruments: Ott 54. - 
 Riefler 61. -- Sydow 120. -- Tes- 
 dorpf 124. 
 
 Electrical Instruments and Ap- 
 pliances: Hartmann & Braun 160. 
 
 Electro - Therapeutical Instru- 
 ments: Hirschmann 19. Reiniger, 
 Gebbert & Schall 58. 
 
 Forrestry, Appliances for: Stau- 
 dinger & Co. 99. Tesdorpf 124. 
 
 Cwasmeter: Kromschro'der 158. 
 
 Glass Instruments and Applian- 
 ces: Bock 14. Niehls 53. Schmidt 
 & v. d. Eltz 66. Schultze 92. - 
 
 - Uebe 135. - Kiichler & Sohne 
 151. Alt, Eberhardt & Jaeger 151. 
 
 - Greiner 152. - - Gundelach 153. 
 Schilling 155. Lindenlaub 156, 
 
 - Strasser & Rhode 156. 
 
 Hygrometers: Bohne 11. 
 
 L^aryngological Instruments: 
 Doerffel & Farber 14. Sydow 120. 
 
 Levellinglnstruments: Butenscho'n 
 16. Ott 54. Tesdorpf 124. 
 
 Levels: Pessler 58. 
 
 mathematical Instruments: Bu- 
 tenscho'n 16. Ott 54. Riefler 61. 
 
 Measures: Bube 158. 
 
 Meteorological Instruments: 
 Bohne 11. Bock 14. Lufft 47. 
 
 - Moeller 51. Fuess 181. 
 Micro logical Instruments: Jung 24. 
 Microscopes: Schieck 66. Schmidt 
 
 & Haensch 67. - - Voigt & Hoch- 
 gesang 137. Zeiss 145. Fuess 181. 
 
 Microtomes: Jung 24. 
 
 Mineralogical Appliances: Voigt 
 & Hochgesang 137. Fuess 181. 
 
 Ophthalmological Instruments: 
 Doerffel & Farber 14. Jung 28. - 
 Sydow 120. 
 
Optical Instruments and Appli- 
 ances: Halle 17. - - Krttss 42. - 
 Merz 49. Schieck 66. Schmidt 
 & Haensch 67. Schulze & Bartels 
 94. Schott & Genossen 96. Steeg 
 & Reuter 97. Steinheil Sohne 103. 
 -Voigtlander & Sohn 141. Zeiss 
 145. 
 
 Pendulum Apparatus: Riefler 61. 
 
 Photographic Appliances: Schulze 
 
 & Bartels 94. Steinheil S8hne 103. 
 
 - Voigtlander & Sohn 141. Zeiss 
 145. 
 
 Photometric A ppli a nces:Krtiss 42. 
 
 - Schmidt & Haensch 67. 
 Physical Apparatus: Kohl 35. - 
 
 Krttss 42. Schmidt & Haensch 67. 
 Staudinger & Co. 99. - - Steinheil 
 Sohne 103. -- Voigt & Hochgesang 
 137. Zeiss 145. Gebhardt 147. 
 Physiological Instruments: Doerf- 
 fel & Farber 14. - - Jung 28. - 
 Sydow 120. 
 
 Polarizing Appliances: Krttss 42. 
 Schmidt & Haensch 67. Steeg 
 
 & Reuter 97. 
 Polarizing Prisms: Halle 17. - 
 
 Steeg & Reuter 97. 
 
 Saccharometers: Schmidt & Haensch 
 
 67. Schultze 92. 
 Spectroscopical Instruments and 
 
 Appliances: Krtiss 42. Schmidt 
 
 & Haensch 67. Steinheil Sohne 103. 
 Surveying Instruments: Buten- 
 
 schOn 16. Ott 54. Tesdorpf 124. 
 
 Theodolites: Butenschon 16. Ott 
 54. Tesdorpf 124. 
 
 Thermometers: Bohne 11. Bock 
 14. Moeller 51. Schmidt & v. d. Eltz 
 66. Schultze 92. Uebe 135. - 
 Standardizing Institute 150. Ktich- 
 ler & Sohne 151. Alt, Eberhardt 
 & Jaeger 151. - - Greiner 152. - 
 Fuess 181. 
 
 marks: Fuess 181. 
 
 Julius Bahike, Berlins. 
 

 
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 UNIVERSITY OF CALIFORNIA LIBRARY 
 
 
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