THE NATIONAL PHYSICAL LABOBATORY. 135 



Rapps 1878 .65 



English Glass .15 



Ver Deer .08 



16"' .05 



59'" .02 



ANALYSIS OF GLASSES. 



SiO. Na.,0 CaO AI..O3 ZnO B0O3 

 16'" — 67.5 14 7 2.5 7 2 



59'" — 72 11 5 12 



Weber had found in 1883 that glasses which contain a mixture of 

 soda and potash give a very large depression. He made in 1883 a glass 

 free from soda with a depression of 0°.l. The work was then taken 

 up by the Aichungs Commission, the Eeichsanstalt, and the Jena 

 factory. Weber's results were confirmed. An old thermometer of 

 Humboldt's containing 0.86 per cent, of soda and 20 per cent, of potash 

 had a depression of 0°.06, while a new instrument, in which the per- 

 centages were 12.7 per cent, and 10.6 per cent., respectively, had a 

 depression of 0°.65. An English standard, With 1.5 per cent, of soda, 

 12.3 per cent, of potash, gave a depression of 0°.15, while a French 

 'Ver deer' instrument in which these proportions were reversed gave 

 only 0°.08. It remained to manufacture a glass which should have a 

 low depression and at the same time other satisfactory properties. The 

 now well-known glass 16"' is the result. Its composition is shown in 

 the table. The fact that there was an appreciable difference between 

 the scale of the 16"' glass and that of the air thennometer led to 

 further investigation, and another glass, a borosilicate, containing 12 

 per cent, of boron, was the consequence. This glass has a still smaller 

 depression. As a result of this work Germany can now claim that 'the 

 manufacture of thermometers has reached in Germany an unprece- 

 dented level and now governs the markets of the world.' 



Previous to 1888 Germany imported optical glass; at that date 

 nearly all the glass required was of liome manufacture. Very shortly 

 afterwards an export trade in raw glass began, which in 1898 was 

 v^orth £30,000 per annum, while the value of optical instruments, such 

 as telescopes, field glasses, and the like, exported that year was over 

 £250,000. Such are the results of the application of science, i. e., 

 organized common sense, to a great industry. The National Ph3^sieal 

 Laboratory aims at doing the like for England. 



The question of standardization of patterns and designs is probably 

 too large a one to go into on the present occasion. Some months ago a 

 most interesting discussion of the subject took place at the Institution 

 of Electrical Engineers. To my mind there is no doubt that the 

 judicious adoption of standard types combined with readiness to scrap 

 old patterns, so soon as a real advance or improvement is made, is 

 necessary for progress. One who has been over some good German 



