OF ARTS AND SCIENCES. 231 



VIII. 



RESEARCHES UPON THE PHOTOGRAPHY OF PLAN- 

 ETARY AND STELLAR SPECTRA. 



By the late Henky Draper, M. D., LL. D. 



With an Introduction hy PuoFESSOR C. A. YouNG, a List of the Photo- 

 graphic Plates in Mrs. Draper^s Possession, and the Results of the Meas- 

 uremeiU of these Plates by Professor E. C. Pickering. 



Presented April 11, 1883. 



Introduction. 



The early successes of Dr. Draper in the construction of liis 15^7-inch 

 reflector, and his photography of the moon, together with his studies 

 in spectrum photography in 1SG9 and 1870, led him to desire to extend 

 his work to the investigation of stellar spectra. It was with this 

 object specially in view that he constructed in 1869 and 1870 his 

 great 28-inch silvered glass reflector, which was finally completed and 

 ready for work in 1871, and in May, 1872, he obtained his first photo- 

 graphs of the spectrum of a Lyraj, by merely inserting a quartz prism 

 in the path of the rays just inside the focus of the small mirror. The 

 plates obtained on this occasion failed, however, to show any lines. 



In August of the same year he succeeded by the same method in 

 getting plates showing four lines in the spectrum of the same star, the 

 least refraiiiiible line beins; near G. 



Other lines of work connected with investigations of the solar spec- 

 trum, and with the superintendence of the photographic preparations 

 for the transit of Venus in 1874, occupied most of Dr. Draper's time 

 for the next two or three years. 



In 1875 he obtained a fine 12-inch refractor from A. Clark & Sons, 

 which he mounted upon the same stand with his 28-inch reflector, and 

 in 1876 he resumed his operations upon stellar spectra, and obtained a 

 number of photographs, some of them with this 12-inch instrument 

 and some with the 28-inch. 



In the summer of 1880 he exchanged the 12-inch instrument for an 

 11-ihch by the same makers, the new instrument having a special cor- 



