In order to facilitate his astronomical observations, Professor Draper constructed an equatorial telescope, with an aperture of twenty-eight inches, for his private observatory at Hastings, on the Hudson. This telescope was the work of his own hands, and when completed was the largest one of the kind in the United States. His astronomical investigations were principally of a photographical character. He was peculiarly adapted to this kind of work, since he had studied photography with his father, who was a pioneer in the photographic art, having taken the first photographic likeness of the human face ever obtained. By means of his large telescope, Professor Draper was able to take the largest and finest photographs of the heavenly bodies ever obtained, and by this means greatly advanced the interests of science. To him was due also the discovery of the gelatino-bromide dry process of photography, which has proven so useful to the art of photography, especially in its application to astronomy. In 1874, after much labor and many costly experiments, he succeeded in obtaining photographs of the fixed lines of stellar spectra, which no one before had ever been able to accomplish. By obtaining photographs of the spectrum of the sun he was able to demonstrate the existence of oxygen in that luminary, a fact never before known to astronomers. His numerous and successful efforts in this line of work rendered him so conspicuous that he was conceded to be without a peer in the department of sidereal photography. As a result of his grand achievements the commissioners appointed by Congress to make arrangements for the observation of the transit of Venus, in 1874, selected him as the superintendent of the photographic department. He performed his duties with such efficiency that Congress ordered a gold medal to be presented to him, bearing the inscription: “He adds lustre to ancestral glory.” In addition to being an expert in astronomical photography Professor Draper was a fine analytical chemist, and in addition to his work as professor of physiology, for several years he taught analytical chemistry in the University. During the last few years of his life he was very much interested in the subject of electricity, and gave much time and study to the problem of overcoming the difficulties of adapting the electric light to practical use, and contributed much valuable information on this point.