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SCIENCE. 



[N. S. Vol. XII. No. 308. 



III. Surveying and Nautical Instruments; — a. 

 Geometrio Instruments, b. Surveying, Mining and 



exploring Instruments, c. Nautical Instruments. 



IV. Meteorological, Geo-magnetic, Thermometrio 

 and Calorimetric Instruments. 



V. Optical Instruments : — a. Photometrical Ap" 

 pliances ; b. Spectroscopes and Optical Measuring In- 

 struments ; c. Microscopes and their auxiliaries ; d. 

 Photomicrography and Projection ; e. Photographic 

 Ojectivea ; f. Hand Telescopes and Terrestrial Tele- 

 scopes ; g. Crystaloptics, Appliances for demonstrat- 

 ing and observing the Phenomena of Light. 



VI. Electrical Measuring Instruments for Scientific 

 Purposes. 



VII. Electro-medical, Physiological and Biological 

 Instruments. 



VIII. Appliances for Chemical and Chemico-phys- 

 ioal Research, Laboratory and Educational Apparatus. 



IX. Drawing and Calculating Appliances. 



X. Appliances for the Examination of Materials 

 and for Special Purposes, Special Tools and Auxili- 



Pollowing the plan of grouping the ex- 

 hibits into sections according to subjects of 

 applied science, it may be profitable to ap- 

 pend a short sketch of the present position 

 of philosophical instrument-making in Ger- 

 many. 



I. German mechanicians found them- 

 selves for the first time in their history face 

 to face with a task of some magnitude 

 when called upon, some seventy years ago, 

 to construct metrological and standardizing 

 appliances for the purpose of determining, 

 under the direction of the great astronomer 

 Bessel, the standards of the old Prussian 

 system of measures. Subsequently, the 

 mechanical arts received an important 

 impetus through the inti'oductiou of the 

 metric system in general and the influence 

 and requirements of the Standardizing 

 Commission in particular. The numerous 

 inducements and hints which German mech- 

 anicians have received from the Stand- 

 ardizing Commission have enabled them to 

 effectually cooperate in the introduction of 

 the metric system both in and outside Ger- 

 many. Opportunities presented themselves 

 for the construction of very exact compara- 



tors, dividing engines, terminal and divided 

 measures, balances of the highest degree of 

 precision, etc.; and while acquitting them- 

 selves of these tasks, German mechanicians 

 have both learned and accomplished much. 

 A considerable portion of the equipment 

 of the ' Bureau international des poids et 

 mesures ' has proceeded from German work- 

 shops. The achievements of Germany in 

 the department of metrological instruments 

 and appliances are prominently demon- 

 strated within the Joint Exhibition of 

 Mechanicians and Opticians by the Special 

 Exhibits of the Imperial Kormal-Aichungs- 

 Kommission [Ofiice of Standards]. 



II. From the measures, the indispensable 

 fundament of all exact research, we pro- 

 ceed to the astronomical instruments. 

 This department is necessarilj' at a disad- 

 vantage inasmuch as the largest and most 

 costly instruments, the large refractors, can 

 only be exhibited under very special cir- 

 cumstances. Hitherto German telescope- 

 makers have supplied large refractors 

 almost exclusively to countries outside 

 Germany, but in this respect they have 

 actively competed with other makers. Re- 

 cently they have been given an opportunity 

 of proving their powers in the construction 

 of the new Potsdam refi-actor, which is not 

 only one of the largest instruments in 

 Europe, but also the first large telescope 

 built for a German observatory, and the 

 results have been brilliant indeed. In the 

 main, the German makers have devoted 

 their attention to the construction of 

 medium-sized and small astronomical in- 

 struments, refractors, transit-circles, alti- 

 tude-circles, heliometers, etc., but with 

 such success that, as regards the precision 

 and delicacy of the individual parts of the 

 instrument, Germany stands now un- 

 rivaled. Recently great progress has been 

 made in the construction of astronomical 

 objectives. The first optician who broke 

 the ice in the important department of 



