430 SPB CTROS CO PI C LIS CO VER Y. 



nearly half a century ago, has been pursued with equal brilliancy to this 

 crowning result — however regarded, this exploit of the younger Draper must 

 command unqualified admiration. 



As has been repeatedly shown in our pages, the early Draper was one of the 

 early and most successful explorers of the chemical relations of the luminous 

 spectrum. He was a pioneer in this line of investigation, and the first to- 

 make extensive use of photography in this branch of research ; and he was 

 so far in advance of his time, that his discoveries were totally unaj)preciated. 

 But he furnished the fortunate men who followed him with their tools to reap 

 the splendid harvest of spectroscopic discoverj^ which has so impressed the 

 world during the last eighteen years. We have never had any doubt that 

 history would set all these things right, but the venerable doctor will at any 

 rate be easy in the assurance that the sceptre has not departed from his 

 family. 



When it was established that the light emitted by vaporized and incan- 

 descent bodies gives spectra by which they may be identified, the passage 

 was rapid to the discovery of chemical substances by the analysis of light.- 

 A study of the spectra of the sun and stars soon gave evidence that they 

 contained forms of matter with which we are familiar upon earth. All the 

 metals, for examj)le, in a state of luminous vapor, yielded bright lines in 

 the spectrum so distinctive in each case that there was no possibility of 

 mistaking them. When these were carefully majiped and compared with 

 the spectra from the sun and stars, such a startling mass of coincidences was- 

 at once disclosed, that there was no escape from the conclusion of a common 

 causality, or that these metals exist also in the stellar bodies. There was- 

 but one serious difficulty. The lines obtained by the combustion of the 

 the metals were bright and colored, while the corresponding lines in the 

 solar and stellar spectra were all dark. Kirchhoff resolved the difficulty in 

 1859, by showing how the bright lines may become dark lines by absorption, 

 in such conditions as the celestial bodies furnish ; and it was thus not only 

 established as a fact that there are various terrestrial' metals in the sun and 

 stars, but their mode of manifestation was brought into complete harmony 

 with theoretical requirements. 



The nebular hypothesis, which had been growing for a century, and 

 which assumed the origin of all the bodies in the solar sj^steni from a com- 

 mon nebulous source, was, of course, at once and profoundly affected by the 

 new revelations. It was proved that there are common elements extensively 

 distributed among celestial bodies, which confirms the hypothesis that they 

 have a common origin. Not only was there new and positive proof of the 

 existence of nebulous matter in the celestial spaces, but the ultimate elements 

 of which material Nature is constituted were shown to be universal, and the 

 nebular hypothesis was thus strongly confirmed. Yet a difficulty at once 

 arose, that thefmain predominant elements terrestrial Nature were not 

 found to exist in the sun and stars. The evidence, of course, was negative, 

 but it was held by many to be weighty, in disjiroof of the nebular doctrine,- 



