SKETCH OF PROFESSOR HENRY DRAPER. 407 



sketch of Henry Draper which appeared in a late number of " Har- 

 per's Weekly ": 



" He had for a companion, friend, and teacher, from childhood, 

 one of the most thoroughly cultivated and original scientific men of 

 the present age, who attended carefully to his instruction, and im- 

 pressed upon him deeply the bent of his own mind in the direction of 

 science. The boy was, in fact, immersed in science from his young- 

 est years, and not merely crammed with its results, but saturated with 

 its true spirit at the most impressible period. He was taught to love 

 science for the interest of its inquiries, and was early put upon the 

 line of original investigation in which he has won his celebrity. Henry 

 Draper inherited not only his father's genius, but his problems of re- 

 search. Dr. John W. Draper was an experimental investigator of 

 such fertility of resources and such consummate skill that the Euro- 

 pean savcmts always deplored his proclivity to literary labors as a 

 great loss to the scientific world. Henry Draper inherited from his 

 father in an eminent degree the aptitude for delicate experimenting, 

 and a fine capacity of manipulatory tact. The elder Draper was one 

 of the founders of the recent science of photo-chemistry. He worked 

 early and brilliantly in the new and fascinating field of the chemistry 

 of light, and more than forty years ago by his extensive contributions 

 to this subject he prepared the way for those who entered to reap the 

 fruits of his labors in the splendid field of spectrum analysis. But 

 the scepter was not to depart from the family. Henry pursued the 

 same line of research, and by his extension of it will have a permanent 

 place among the discoverers of the period." 



Henry Draper's first important scientific investigation was made 

 at the age of twenty, and was embodied in his graduating thesis at 

 the Medical College. It was on the functions of the spleen, which 

 was illustrated by microscopic photography an art then in its in- 

 fancy. Soon after receiving his degree he went to Europe, and while 

 there visited the widely-known observatory of Lord Rosse, and studied 

 the construction and working of his celebrated colossal reflecting 

 telescope. This led him to consider the problem of using reflecting 

 telescopes for the purpose of photographing celestial objects. On his 

 return home he constructed a telescope of this kind of fifteen and a 

 half inches aperture, and with it took a photograph of the moon fifty 

 inches in diameter the largest ever made. His success spurred him 

 on to further improvements, so that he became an adept in grinding, 

 polishing, and testing reflecting mirrors. An equatorial telescope was 

 afterward constructed by him, with an aperture of twenty-eight inch- 

 es, for his observatory at Hastings-on-the-Hudson. The instrument 

 was wholly the work of his own hands, and was designed mainly to 

 photograph the spectra of the stars. After a long series of experi- 

 ments, it was finished in 1872, and has been pronounced by President 

 Barnard as ' probably the most difficult and costly experiment in celes- 



