2 PROCEEDINGS OF THE AMERICAN ACADEMY 



The question of the existence of oxygen in the sun was first seri- 

 ously investigated, we believe, by Dr. Henry Draper, who published 

 in the American Journal of Science for 1877 and 1879, and in foreign 

 journals, papers accompanied by reproductions of his photographs. 

 Dr. Draper was firmly persuaded of the existence of oxygen in the 

 sun's atmosphere, and based this belief upon the apparent coincidence 

 of the lines of oxygen taken in air with certain bright spaces in the 

 sun's spectrum which appeared upon his photographs. 



Prof. John Christopher Draper published a paper in the Ameri- 

 can Journal of Science for 1878, in which he stated his conviction that 

 oxygen exists in the sun; but his line of argument was just the 

 reverse of that of Dr. H. Draper. While the latter apparently proved 

 the existence of oxygen in the sun by the coincidence of its bright 

 lines with bright spaces in the solar spectrum, the former was led to 

 believe that the bright oxygen lines coincided with dark lines in 

 the sun. 



Both observers abandoned the old method of eye observation, and 

 took advantage of the improvements in photography to record the 

 oxygen lines upon a sensitive plate. Dr. H. Draper was led to aban- 

 don Geisler's tubes filled with oxygen, and to employ the electric 

 spark in common air, on account of the greater brilliancy of the lines, 

 while Prof. J. C. Draper still adhered to tubes filled with rarefied 

 oxygen. The oxygen liues had been mapped by previous observers, 

 notably by Thaleu, and Schuster had shown that there were four 

 spectra of oxygen which could be produced under varying conditions 

 of temperature and pressure. 



The photographs of Dr. Henry Draper's oxygen spectrum, together 

 with the juxtaposed solar spectrum, were submitted to the French 

 Academy of Sciences in Paris, June 23, 1879, by M. Cornu. From 

 the remarks of M. Faye we make the following extract : — 



" Dr. H. Draper has, however, succeeded in discovering oxygen, 

 not in the chromosphere, but in the photosphere, where it discloses 

 itself by bright lines. It is obvious that this gas is dissociated at a 

 depth, and is immediately taken up by multiple combinations in the 

 region and at the temperature of the brilliant surface. I see in these 

 facts the hope of a confirmation, and above all of an extension, of 

 the views I have put forth on the constitution of the sun ; but what- 

 ever may be the fate that the progress of spectrum analysis reserves 

 to them, I express here my admiration for the discovery of Mr. 

 Draper, and I hope that his results, so well confirmed by the photo- 

 graphic proofs that our learned member, M. Cornu, has shown the 



