374 Chronicles. of Science. [July, 
attractive influence to travel in its present orbit. Discovered in 
1846, the comet was missed at the perihelion passage of 1851, 
seen in 1857, again missed in 1862, and re-discovered, by three 
observers almost simultaneously, in April of the present year. It 
will travel across the southernmost parts of the constellations 
Ursa Major and Bootes, remaining throughout invisible to the 
naked eye. . 
Mr. Huggins has subjected Brorsen’s comet to spectroscopic 
analysis. The results are exceedingly interesting. It will be re- 
membered that two former comets, examined by Mr. Huggins, 
exhibited, so far as the light of their nuclei was concerned, 
spectra closely resembling those of the gaseous nebule. Their 
come appeared to shine by reflected light. The spectrum of the 
present comet is very different. It consists of three bright bands, 
somewhat resembling those seen by Donati in the spectrum of the 
comet which bears his name. The length of the bands shows that 
they are not due to the steller nucleus of the comet alone, but are 
produced by the light of the coma, or at least of its brighter 
portions. In one of the bands Mr. Huggins could occasionally 
detect two bright lines, shorter than the band, and therefore pre- 
sumably due to the nucleus alone. This view of their origin was 
confirmed by the circumstances that they were not visible when the 
middle of the comet was not upon the slit, whereas the nebulous 
band on which they were projected continued visible so long as any 
part of the comet except its extreme margin was upon the shit. A 
very faint continuous spectrum was also visible.. The brightest 
band was found to lie nearly in the same position as the brightest 
line of the nebule, which is coincident with the double line in the 
spectrum of nitrogen. 
It appears, then, that Brorsen’s comet resembles the two others 
(and probably Donati’s) in this respect, that the nucleus and part of 
the coma shine by their own light. But whereas only the bright- 
est part of the come of the two other comets shone by their own 
light, it appears that nearly the whole of the coma of Brorsen’s 
comet is self-luminous. 
We have to record a most interesting application of spectro- 
scopic analysis to a different subject of astronomical research. It is 
well known that what is called the proper motion of the stars, or 
their apparent change of place on the sidereal concave, is in reality 
only a portion of their true motion—the transverse portion. The 
other part—or the motion of a star directly towards or from the 
eye—produces no effects perceptible by the telescope. It would 
require thousands of years before any motion of this sort could 
produce an appreciable change in a star’s apparent brilliancy ; but 
by a subtle application of spectroscopic analysis, Mr. Huggins has 
led the way in a process of research which promises to afford us 
