90 Henry Draper. 
was illustrated with microphotographs of great excellence. 
This early study of photography led him to the discovery of 
the value of palladious chloride as an intensifier. From this 
time dates his interest in the photographic studies in which he 
afterward attained such eminence. Shortly after graduation 
he spent a year in Kurope, and made a visit to Lord Rosse at 
Parsonstown, Ireland. Here he saw the great reflector so well 
known to science, and became very much interested in it, 
because of its photographic possibilities. Upon his return he 
set about constructing a metal speculum fifteen inches in diam- 
glass 153 inches in diameter. The details of the construction 
and mounting of these mirrors were published as a monograph, 
in 1864, by the Smithsonian Institution. With this instrument 
a great amount of astronomical photography was done, the piece 
of work best known being his photograph of the moon, In per- 
fection of detail it was far in advance of any previous attempt. 
The original negatives, of which over 1500 were taken, were 
photographie corrector. A five-inch finder completed this 
unrivalled photo-telescopic battery. All these instruments 
laboratory and the workshop. ough a wooden building of 
but one story, unpretending in appearance, its internal arrange- 
ments were admirable, and its facilities for astronomical photo- 
graphy entirely unsurpassed. 
The wo t the observatory was done chiefly during the 
summer months; Dr. Draper residing then at his country place 
at Dobbs Ferry, two miles distant. In the winter, he carried 
