Oxygen in the Sun. 303 



occupied many eminent physicists ; but the fact that the 

 latest and most complete investigations have left the minds of 

 scientific men still in doubt, has led the writers to take up 

 the question again with more perfect and powerful apparatus 

 and increased facilities, in order, if possible, to add something 

 to the knowledge of the subject. 



The question of the existence of oxygen in the sun was 

 first seriously 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 

 i American 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 observa- 

 tion, and took advantage of the improvements in photography 

 to record the oxygen lines upon a sensitive plate. Dr. H. 

 Draper was led to abandon Geissler'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 lines had been mapped by previous observers, notably 

 by Thalen, 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 tempe- 

 rature 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- 



