NOVBMBBE 23, 1900.] 



SCIENCE. 



783 



Zeiss Apochromatic objectives, which, in 

 conjunction with the compensating eye- 

 pieces, yield a much more perfect correction 

 of the chromatic and spherical aberrations 

 than was previously attainable. We believe 

 that we are not going too far by saying that 

 to Professor Abbe is due the world-wide 

 fame of German microscope construction. 

 This reputation is not limited to the micro- 

 scope itself, but to all its accessories, and em- 

 braces also microtomes, photo-micrographic 

 and projection appliances and, in particu- 

 lar, photographic objectives, the construc- 

 tion of which has undergone wonderful 

 changes since the introduction of the Jena 

 glasses. The enormous exigencies of mod- 

 ern artificial illumination has given rise to 

 many improvements in photometry. In 

 this department the path has been smoothed 

 by the efforts of the Imperial Physical and 

 Technical Institute, and photometers are 

 now made by which the intensity of a 

 luminary can be measured with a degree of 

 accuracy within J per cent. The result is 

 that German photometers enjoy a predomi- 

 nant popularity. —Germany, the cradle of 

 spectrum analysis, occupies naturally an 

 important position in the manufacture of 

 spectrum appliances. The construction of 

 these instruments, varying from the largest 

 and finest spectrometers for astronomical, 

 physical and chemical research, to the 

 smallest hand spectroscopes, employs a large 

 number of establishments. The same ap- 

 plies to the manufacture of polariscopic ap- 

 pliances, which have a wide reputation and 

 command a particularly large market in the 

 sugar trade. — JSTo less importance attaches 

 to the optical measuring instruments de- 

 signed for the special requirements of 

 physicists, chemists, mineralogists, etc., 

 which are made with astronomical precision, 

 so as to satisfy the highest exigencies of 

 modern research. Among these we may 

 mention the crystaloptic instruments and 

 those for studying the theory of the nature 



of light. — In the construction of telescopes 

 Germany has, in addition to general im- 

 provements, achieved a triumph, which has 

 given her a great advantage. We are 

 referring to the new form of binocular 

 telescopes, in which, by the interposition of 

 prisms, the dimensions of terrestrial tele- 

 scopes are reduced to their lowest limits, 

 while, at the same time, the defining power, 

 light-gathering power and the stereoscopic 

 effect are greatly increased as compared with 

 the old types. The invention of these tele- 

 scopes has created a wide demand in the 

 army and navy. Very considerable, too, 

 is the industry in optical auxiliaries, prisms, 

 quartz and calc-spar preparations, etc., in 

 which Germany excels both in quality and 

 productiveness. 



VI. The manufacture of electrical meas- 

 uring instruments for scientific purposes 

 has, in Germany, kept pace with the great 

 strides made in electrical engineering. A 

 number of prominent firms apply them- 

 selves to this technical branch and have 

 made themselves a good name. This in- 

 dustry has likewise profited by the funda- 

 mental labors of the Imperial Physical and 

 Technical Institute, in particular by the 

 establishment of standards and by impor- 

 tant investigations. We may here mention 

 the introduction of new resistance materials, 

 called manganine and constantan, which 

 are not affected by changes of temperature 

 and are now introduced by nearly all Ger- 

 man firms occupied with the manufacture 

 of electrical measuring instruments. Men- 

 tion should also be made of the work ac- 

 complished in standard cells, which facili- 

 tate the application of the so-called methods 

 of compensation for accurately measuring 

 the strength and E.M.F. of electrical cur- 

 rents. This is, therefore, another depart- 

 ment where the influence of scientific re- 

 search has been felt in practical manufac- 

 ture. 



VII. Electro-medical appliances are also. 



