1384 H. Draper—Photographs of the Spectrum of the Comet. 
Art. XXIV.—Note on Photographs of the Spectrum of the Comet 
of June, 1881; by Professor HENRY DRAPER, M.D. 
THE appearance of a large comet has afforded an opportunity 
of adding to our knowledge of these bodies by applying to it a 
new means of research. Owing to the recent progress in pho- 
tography, it was to be hoped that photographs of the comet 
and even of its spectrum might be obtained and peculiarities 
invisible to the eye detected. For such experiments my 
observatory was prepared, because for many years its resources 
ad been directed to the more delicate branches of celestial 
photography and spectroscopy, such as photography of stellar 
spectra and of the nebule. ore than a hundred photographs 
of spectra of stars have been-taken, and in the nebula of Orion 
details equal in faintness to stars of the 14:7 magnitude have 
been photographed. 
It 
when an exposure of 162 minutes was 
given, the tail impressed itself to an extent of nearly ten 
degrees in length. 
which would show the continuous spectrum of the nucleus 
and the banded spectrum of the coma. After an exposure 0 
eighty-three minutes, a strong picture of the spectrum of the 
nucleus, coma and part of the tail was obtained, but the banded 
spectrum was overpowered by the continuous spectrum. 
I then applied the two-prism spectroscope used for stellar 
spectrum photography, anticipating that although the diminu- 
tion of light ae , serious after passing through the shit, 
two prisms and two object glasses, yet the advantage of being 
being more weakened than the banded by the increased disper 
sion the latter would become more distinct. 
