30 PHYSICS 



As time rolls on, the greatest names more and more fully absorb the 

 activity of a whole epoch. 



Metrology 



Finally, it will hardly be possible to consider the great advances 

 made in physics except on the theoretical side. Of renowned experi- 

 mental researches, in particular of the investigations of the con- 

 stants of nature to a degree of ever-increasing accuracy, it is not prac- 

 ticable to give any adequate account. Indeed, the refinement and 

 precision now demanded have placed many subjects beyond the 

 reach of individual experimental research, and have culminated in 

 the establishment of the great national or international laboratories 

 of investigation at Sevres (1872), at Berlin (1887, 1890), at London 

 (1900), at Washington (1901). The introduction of uniform inter- 

 national units in cases of the arts and sciences of more recent develop- 

 ment is gradually, but inexorably, urging the same advantages on 

 all. Finally, the access to adequate instruments of research has 

 everywhere become an easier possibility for those duly qualified, and 

 the institutions and academies which are systematically undertaking 

 the distribution of the means of research are continually increasing 

 in strength and in number. 



Classification 



In the present paper it will be advisable to follow the usual pro- 

 cedure in physics, taking in order the advances made in dynamics, 

 acoustics, heat, light, and electricity. The plan pursued will, there- 

 fore, specifically consider the progress in elastics, crystallography, 

 capillarity, solution, diffusion, dynamics, viscosity, hydrodynamics, 

 acoustics; in thermometry, calorimetry, thermodynamics, kinetic 

 theory, thermal radiation; in geometric optics, dispersion, photo- 

 metry, fluorescence, photochemistry, interference, diffraction, polar- 

 ization, optical media; in electrostatics, Volta contacts, Seebeck 

 contacts, electrolysis, electric current, magnetism, electromagnetism, 

 electrodynamics, induction, electric oscillation, electric field, radio- 

 activity. 



Surely this is too extensive a field for any one man! Few who are 

 not physicists realize that each of these divisions has a splendid and 

 voluminous history of development, its own heroes, its sublime class- 

 ics, often culled from the activity of several hundred years. I repeat 

 that few understand the unmitigatedly fundamental character, the 

 scope, the vast and profound intellectual possessions, of pure physics; 

 few think of it as the one science into which all other sciences must 

 ultimately converge or a separate representation would have been 

 given to most of the great divisions which I have named. 



