446 HENRY DRAPER. 



the Coincidence of the Bright Lines of the Oxygen Spectrum witli 

 Bright Lines in the Solar Spectrum," 1877. " Eclipse of the Sun in 

 July, 1878" (published in 1878). "Photographing the Spectra of the 

 Stars and Planets," 1879. " Photography of Jupiter's Spectrum, and 

 Photographs of the Nebula in Orion," 1880. "Photographs of the 

 Spectrum of the Comet of June, 1881." 



His Avork upon the photography of stellar spectra continued from 

 1872 until his death, and he has left a large number of valuable pho- 

 tographs, which promise to exercise great influence upon the direction 

 of modern astronomical investigation. Although he began with the 

 use of reflectors, most of his subsequent astronomical work was done 

 with an eleven and a half inch refractor. With this instrument he 

 made his well-known photographs of the Nebula of Orion. 



In 1874 he superintended the photographic work of the Transit of 

 Venus Commission, and the United States government in honor of his 

 able work caused a special gold medal to be struck, which bears upon 

 the face the words, " Decori decus addit avito," and upon the reverse, 

 " Famam extendere factis, hoc virtutis opus." 



Perhaps his most famous investigation is that upon the presence 

 of oxygen in the sun. The results of this investigation are, if fully 

 substantiated by subsequent observers, extremely important. The 

 method of procedure was to photograph the solar spectrum side by 

 side with that of oxygen. The entire investigation is well worthy of 

 study, not from its results alone, but from its refined and delicate 

 methods. In the photograplis the bright lines of the oxygen spectrum 

 coincide with certain bright spaces between the dark lines of the solar 

 spectrum. In regard to the conclusions of Dr. Draper, Prof. C. A. 

 Young of Princeton remarks : " Naturally there has been some scep- 

 ticism and discussion as to the correctness and soundness of his con- 

 clusions ; but no one with an unprejudiced mind can, we think, resist 

 the evidence after careful examination of the plates, especially those 

 obtained during his second and still more elaborate investigation of 

 the subject in 1878-79." This investigation illustrates the scientific 

 position of Dr. Draper better, perhaps, than any we can choose. His 

 early training as a chemist, his active years spent in the mysteries of 

 photography, and his ample fortune, fitted him to undertake such an 

 investigation. It is by reflecting upon the methods of this work, and 

 upon its results, tlaat we can appreciate liow much the scientific world 

 has lost. At present, photography seems the most potent means for 

 studying the light of the stars, for unravelling the mysteries of the 

 sun, and for estimating the energy of molecular movements in general. 



