118 H. Draper—Photograph of Jupiter’s Spectrum. 
is, CaB,Si,O,, or Ca,Si0,+B,Si,0,,... The formula requires: 
Silica, 48-78, boron trioxide, 28°46, lime, 22°76=100. These 
results set at rest any further question as to the chemical com- 
position of danburite. It does not appear, however, that there 
is any immediate relation between danburite and topaz in chem- 
ical composition, which, considering the similarity in crystal- 
line form, is rather remarkable. 
ognostic characters.—The pyrognostic characters of this 
species are sufficiently important to be here repeated. B. B 
the mineral glows, fuses gently at 3°5 to a colorless glass, im- 
parting to the flame the characteristic green color due to boron. 
On cooling, the assay loses its transparency and becomes milk- 
white. In the closed tube it phosphoresces brilliantly with a 
reddish yellow light. The mineral is slightly acted upon by 
hydrochloric acid, sufficiently so to give the reaction for boric 
acid with turmeric paper. When previously ignited to the 
point of fusion the mineral gelatinizes with acid. 
Comparison with the original danburite.—A comparison be- 
tween the characters of the danburite from Russell, N. Y., 
and those of the same species from the original ipee iy 
is there apparent divergence. In regard to this there is only to 
be said that the earlier determinations upon the Danbury mineral 
were made on imbedded fragments in feldspar where apparent 
planes, at best of a problematical nature, certainly did not rep- 
resent the true crystalline form of the species 
Art. XVI.—On a Photograph of Jupiter's Spectrum, showing 
Evidence of Intrinsic Light from that Planet; by Professor 
Henry Draper, M.D. 
[Read before the Royal Astronomical Society, May 14th, 1880, and extracted from 
the Monthly Notices. ] 
THERE has been for some years a discussion as to whether 
the planet Jupiter shone to any perceptible extent by his own 
intrinsic light, or whether the illumination was altogether 
derived from the sun. Some facts seem to point to the con- 
clusion that it is not improbable that Jupiter is still hot 
enough to give out light, though perhaps only in a periodic or 
eruptive manner. 
It is obvious that spectroscopic investigation may be usefully 
employed in the examination of this question and I have inci- 
dentally, in the progress of an allied inquiry,* made a photo- 
* See paper “On Photographing the Spectra of the Stars and Planets,” read 
before the National Academy of Sciences, Oct. 28, 1879, and published in this 
Journal, Dec., 1879, and in Nature, Nov. 27, 1879. 
