SPECTRUM ANALYSIS OF THE HEAVENLY BODIES. 143 
of light. Since they shine by reflecting the sun’s light, their spectra re- 
semble the solar spectrum, and the only indications in their spectra which 
may become sources of knowledge to us are confined to any modifications 
which the solar light may have suffered either in the atmospheres of the 
planets, or by reflection at their surfaces. 
Moon.—On the moon the results of their observations have been negative. 
The spectra of the various parts of the moon’s surface, when examined under 
different conditions of illumination, showed no indication of an atmosphere 
about the moon. The speaker also watched the spectrum of a star, as the 
dark edge of the moon advanced towards the star, and then occulted it. No 
signs of a lunar atmosphere presented themselves. 
Jupiter.—In the spectrum of Jupiter, lines are seen which indicate the 
existence of an absorptive atmosphere about this planet. In fig. 3, Plate III. 
these lines are presented as they appeared when viewed simultaneously with 
the spectrum of the sky which, at the time of observation reflected the light 
of the setting sun. One strong band corresponds with some terrestrial atmo- 
spheric lines, and probably indicates the presence of vapours similar to those 
which are about the earth. Another band has no counterpart amongst the 
lines of absorption of our atmosphere, and tells us of some gas or vapour 
which does not exist in the earth’s atmosphere. 
Saturn.—The spectrum of Saturn is feeble, but lines similar to those 
which distinguish the spectrum of Jupiter were detected. These lines are 
less strongly marked in the ansze of the rings, and show that the absorptive 
power of the atmosphere about the rings is less than that of the atmosphere 
which surrounds the ball. Janssen has quite recently found that several of 
the atmospheric lines are produced by aqueous vapour. It appears to be 
very probable that aqueous vapour exists in the atmospheres of Jupiter and 
Saturn. 
Mars.—On one occasion some remarkable groups of lines were seen in the 
more refrangible part of the spectrum of Mars. These may be connected 
with the red colour which distinguishes this planet. 
Venus.—Though the spectrum of Venus is brilliant and the lines of 
Fraunhofer were well seen, no additional lines affording evidence of an 
atmosphere about Venus were detected. The absence of lines may be due 
to the circumstance that the light is probably reflected, not from the 
planetary surface, but from clouds at some elevation above it. The light 
which reaches us in this way by reflection from clouds would not have been 
exposed to the absorbent action of ae lower and denser strata of the planet’s 
atmosphere. 
Tuer Fixep Srars. 
The fixed stars, though immensely more remote, and less conspicuous in 
brightness than the moon and planets, yet because they are original sources 
of light, furnish us with fuller indications of their nature. The telescope 
was appealed to in vain, for in the largest instruments the stars remain 
diskless—brilliant points merely. 
The stars have, indeed, been represented as suns, each upholding a dependent 
family of planets. This opinion rested upon a possible analogy alone. It was 
not more than a speculation. We possessed no certain knowledge from 
observation of the true nature of those remote points of light. This long and 
earnestly coveted information is at last furnished by spectrum analysis. .We 
are now able to read in the light of each star some indications of its nature. 
The speaker referred to two bright stars which had been examined with 
great care. The spectra of these stars are represented in Plate IV. 
