4 W. J. MCGEE 



knowledge, during the half century; but nobler still have 

 been the tasks of the fewer searchers who have been able to 

 span two or more specialties, and to simplify knowledge by 

 co-ordination. The solidarity of science is well illustrated by 

 the work of the physicist Bunsen and the chemist Kirchoff, 

 both of Germany, who in 1859 combined their specialties (as 

 few great men are able to do) and blent ideas in the inven- 

 tion of the spectroscope, which has revolutionized several 

 sciences. By aid of this device, later chemists and physicists 

 have discovered new facts and made some of the most impor- 

 tant generalizations of the time ; by its daily aid, the metallur- 

 gist appHes the Bessemer process, which has revolutionized 

 the steel production of the world; aided by a derivative de- 

 vice (the bolometer), Langley has been able to measure and 

 weigh the light and combustion rate of the firefly lamp, and 

 thus to gain a new point of view in physiology. Still greater 

 has been the service of the spectroscope to the astronomer; 

 for it has brought, as it were, to the test tube and crucible, our 

 sun and other suns, and the luminous planets and comets, so 

 that their substance may be analyzed hardly less definitely 

 than the rocks beneath our feet; it even enables the astrono- 

 mer to read from the shifting lines of the spectrum the rela- 

 tive motions of stars long enough to be fixed. This applica- 

 tion of the spectroscope marks the most noteworthy advance 

 in astronomy not only of the half century but of all time. 

 No key ever unlocked sublimer revelations or more inspiring 

 vistas than this instrument which opened the door of the 

 new astronomy. 



A few of the principal advances in science, made in the 

 last fifty years, may be noted. 



Europe and America have contributed to astronomy 

 in fairly equal measure. The spectroscope was the gift of 

 the older country, and some of its most brilliant products 

 were brought forth by Huggins and other transatlantic 

 students; yet spectroscopy was revolutionized by the Amer- 

 ican physicist Rowland, with his exquisitely deHcate 

 diffraction gratings and his marvelous mechanism for pro- 

 ducing them. So, too, the photometric work of the Pick- 

 erings in Harvard observatory, with its adjunct in Peru, 



