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received from Saturn at successive oppositions, and - deducting” 
therefrom that portion which calculation (founded on the light 
received from the planet when the ring disappears) shows to be 
due to the globe, it would be possible to determine according to 
what law the ring varies in brilliancy as its amount of opening 
changes, and thus to determine generally what may be the 
nature of the ring’s surface. 
The result of the application of spectroscopic analysis to the 
rings has been at once interesting and perplexing. The spec- 
trum of the planet’s light exhibits certain absorption-lines 
indicative of the presence of vapour. Now Mr. Huggins has 
discovered that the same lines are present in the spectrum of the 
ring’s light also ; and that, of the two, the latter spectrum exhi- 
bits these dark lines somewhat the more distinctly. This result 
is remarkable. It indicates that the amount of vapour through 
which the light from the globe has passed before reaching us is 
less than the amount passed through by the light from the 
rings. We are accustomed to recognise the probability that the 
globe of Saturn is surrounded by an atmosphere proportional in 
extent to the enormous volume of the planet. On the other 
hand, the small bodies forming the rings if they had atmo- 
spheres at all, would have vapourous envelopes so limited in 
extent, one would suppose — the volume of each of these satel- 
lites being so minute — that the most powerful spectroscope 
should fail to reveal any trace of its existence. Supposing them 
to resemble our own satellite, but on a much smaller scale, their 
atmospheres would be a million-fold too small to produce any 
distinctive dark lines in the spectrum of their light ; for though 
the moon is so much the nearest of all the celestial bodies, its 
spectrum has no dark lines other than those belonging to it as 
formed by reflected solar light. When we remember that Saturn, 
when at his least distance from the earth, is upwards of 820 
millions of miles from us, or more than 3,000 times farther from 
us than the moon is, the visibility of distinctive dark lines in the 
spectrum of the ring will appear one of the most interesting and 
remarkable results of spectroscopic research. It would be per- 
plexing in the extreme if we supposed the rings to be conti- 
nuous bodies ; but accepting, as we are bound to do, the theory 
that they consist of flights of minute satellites, the result be- 
comes one of the most surprising that can well be imagined. 
The explanation I would venture to offer of this strange 
phenomenon will, I fear, appear to many unduly speculative, if 
even it do not seem opposed to well-known physical laws. In 
an appendix to my treatise on Saturn, I have maintained the 
view that the moon has so thoroughly parted with its original 
internal heat that even the gases once subsisting on its surface 
have been transformed into the solid form. I was aware when 
