8 PROCEEDINGS OF THE AMERICAN ACADEMY 



existence of the element in the sun is not conclusive. It is supported, 

 however, if there is any striking peculiarity in the lines of the element 

 which is reproduced in the corresponding lines in the solar spectrum. 

 Thus the nebulous character of the lines of magnesium is perfectly 

 reproduced in the corresponding lines in the solar spectrum. The test 

 of coincidence, therefore, requires primarily a normal spectrum and the 

 highest possible dispersion. The earlier observers were limited to in- 

 struments of small dispersion, and the entire number of lines observed 

 in the solar spectrum was small compared with that given by the best 

 modern apparatus. The chances for an apparent coincidence were 

 therefore much greater, and evidence of a very misleading character 

 could be obtained. 



In Dr. H. Draper's published photograph, the coincidence of the 

 greater part of the oxygen lines with bright bands in the solar spectrum 

 is quite striking ; and it is not a matter of surprise that he was led to 

 conclude the connection between the two spectra to be a physical 

 one, and to announce the existence of oxygen in the sun as proved. 

 Instances are not infrequent where instrumental imperfection or lack 

 of power has led to results unsupported by later and more powerful 

 research. Witness the spots of Venus of the older observers. Now 

 when we apply to the spectra of the sun and oxygen a dispersion and 

 definition that show the minute detail of each, the "bright bands" at 

 once vanish, or no longer appear as such, and all the apparent connec- 

 tion between them and the oxygen lines disappears also. The bright 

 bands of Dr. H. Draper's spectrum are found to be occupied by nu- 

 merous dark lines, of various degrees of intensity ; but the hypothesis 

 of Prof. J. C. Draper, that these are the true representatives of the 

 oxygen lines, is rendered untenable by the lack of any systematic 

 connection between the two. It happens quite frequently that an oxy- 

 gen line falls centrally upon the space between two dark lines of the 

 solar spectrum, but not more frequently than we might expect as a 

 matter of chance, when we consider the vast number of lines and 

 spaces ; and the fact that the spaces are no brighter than the sur- 

 rounding background of the solar spectrum would not seem to permit 

 of their interpretation as bright lines. 



The subject of bright lines in the solar spectrum is one upon which 

 men will probably differ, and we have sought information upon it. Of 

 course there is no a priori reason why such bright lines should not 

 exist, as they do in many stars ; but we have photographed the sun's 

 spectrum every day that the sun has shone for nearly five months, 

 without finding a line that could with certainty be pronounced 



