EDITOR'S TABLE. 



61 



9 



pages,' the elder 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 dis- 

 coveries were totally unappreciated. 

 But he furnished the fortunate men who 

 followed him with their tools to reap 

 the splendid harvest of spectroscopic 

 discovery, which has so impressed the 

 woi'ld daring the last eighteen years. 

 We have never had any doubt that his- 

 tory 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 sub- 

 stances 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 fa- 

 miliar upon earth. All the metals, for 

 example, 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 mapped and com- 

 pared with the spectra from the sun 

 and stars, such a startling mass of co- 

 iiicidences 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 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 fur- 



1 8ee PopuxAE Science Monthly, vol. iv., p. 

 361 ; vol. is., p. 390. 



nish ; and it was thus not only estab- 

 lished 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 system from a common nebu- 

 lous source, was, of course, at once 

 and profoundly aff'ected by the new 

 revelations. It was proved that there 

 are common elements extensively dis- 

 tributed among celestial bodies, which 

 confirms the hypothesis that they have 

 a common origin. Not only was there 

 new and positive j^roof of the exist- 

 ence 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 the main predominant ele- 

 ments of 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 disproof of the nebular doctrine. 

 If the non-metallic elements, it was 

 said, which form the principal part of 

 terrestrial objects, do not exist in the 

 sun, the derivation of that body and of 

 its encircling planets from the same 

 primeval source is impossible. Dr. 

 Draper has now proved that oxygen in 

 large proportions exists in the sun (and 

 probably nitrogen also) ; and his dis- 

 covery can therefore only be regai'ded 

 as lending further and more powerful 

 confirmation to the nebular hypothesis. 



Dr. Draper's paper, in the American 

 Journal of Science and Arts, is accom- 

 panied by an illustrative diagram, which 

 brings the demonstration before the eye 

 of every reader. It exhibits the spec- 

 trum of the sun, and that which is pro- 

 duced from air, so juxtaposed that the 

 fact and the extent of the identity of 

 the lines in the two representations are 



