244 



SCIENCE. 



EN. S. Vol. XXII. No. 556. 



Let me pass from these generalities, 

 which have been suggested to my mind by 

 the consideration of some of the scientific 

 changes that have taken place during the 

 last hundred years, and let me refer briefly 

 to some of the changes and advances which 

 appear to me to be most characteristic of 

 that period. It is not that I am concerned 

 with a selection of the most important re- 

 searches of the period. Estimates of rela- 

 tive importance are often little more than 

 half-concealed expressions of individual 

 preferences or personal enthusiasms; and 

 though each enthusiastic worker, if quite 

 frank in expressing his opinion, would de- 

 clare his own subject to be of supreme im- 

 portance, he would agree to a compromise 

 that the divergence between the different 

 subjects is now so wide as to have destroyed 

 any common measure of comparison. My 

 concern is rather with changes, and with 

 tendencies where these can be discerned. 



The growth of astronomy has already 

 occupied so large a share of my remarks 

 that few more words can be spared here. 

 Not less, but more, remarkable than the 

 preceding centuries in the actual explora- 

 tion of the heavens, which has been facili- 

 tated so much by the improvements in in- 

 struments and is reinforced to such effect 

 by the cooperation of an ever-growing band 

 of American astronomers, it has seen a new. 

 astronomy occupy regions undreamt of in 

 the older days. New methods have supple- 

 mented the old ; spectroscopy has developed 

 a science of physics within astronomy ; and 

 the unastronomical brain reels at the con- 

 tents of the photographic chart of the 

 heavens which is now being constructed by 

 international cooperation and will, when 

 completed, attempt to map ten million stars 

 (more or less) for the human eye. 



Nor has the progress of physics, alike on 

 the mathematical side and the experimental 

 side, been less remarkable or more restricted 



than that of astronomy. The elaborate and 

 occasionally fantastic theories of the eigh- 

 teenth century, in such subjects as light, 

 heat, even as to matter itself^ were rejected 

 in favor of simpler and more comprehensive 

 theories. There was one stage when it 

 seemed as if the mathematical physicists 

 were gradually overtaking the experimental 

 physicists ; but the discoveries in electricity 

 begun by Faraday left the mathematicians 

 far behind. Much has been done towards 

 the old duty, ever insistent, of explaining 

 new phenomena ; and the names of Max- 

 well, Weber, Neumann, and Hertz need only 

 to be mentioned in order to suggest the 

 progress that has been made in one subject 

 alone. We need not hesitate to let our 

 thoughts couple, with the great physicists of 

 the century, the leaders of that brilliant 

 band of workers upon the properties of 

 matter who carry us on from wonder to 

 wonder with the passage of each successive 

 year. 



Further, it has been an age when technic- 

 al applications have marched at a marvel- 

 ous pace. So great has been their growth 

 that we are apt to forget their comparative 

 youth ; yet it was only the middle of the 

 century which saw the awakening from 

 what now might be regarded as the dark 

 ages. Nor is the field of possible application 

 nearing exhaustion : on the contrary, it 

 seems to be increasing by reason of new dis- 

 coveries in pure science that yet will find 

 some beneficent outcome ' in practice. In- 

 visible rays and wireless telegraphy may be 

 cited as instances that are occupying pres- 

 ent activities, not to speak of radium, the 

 unfolding of whose future is watched by 

 eager minds. 



One gap, indeed, in this subject strikes 

 me. There are great histories of mathe- 

 matics and great histories of astronomy; I 

 can find no history of physics on the grand 

 scale. Some serviceable manuals there are. 



