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 



