s indeed possible, nay more, it is extremely probable,
that the two last-named planets have a greater number of these secondary
bodies revolving around them; but, unfortunately, the Uranian and
Neptunian systems are at such immense distances from us, that even the
magnificent telescopes of to-day can extract very little information
concerning them.

From the distribution of the satellites, the reader will notice that the
planets relatively near to the sun are provided with few or none, while
the more distant planets are richly endowed. The conclusion, therefore,
seems to be that nearness to the sun is in some way unfavourable either
to the production, or to the continued existence, of satellites.

A planet and its satellites form a repetition of the solar system on a
tiny scale. Just as the planets revolve around the sun, so do these
secondary bodies revolve around their primaries. When Galileo, in 1610,
turned his newly invented telescope upon Jupiter, he quickly recognised
in the four circling moons which met his gaze, a miniature edition of
the solar system.

Besides the planets and their satellites, there are two other classes of
bodies which claim membership of the solar system. These are Comets and
Meteors. Comets differ from the bodies which we have just been
describing in that they appear filmy and transparent, whereas the others
are solid and opaque. Again, the paths of the planets around the sun and
of the satellites around their primaries are not actually circles; they
are ovals, but their ovalness is not of a marked degree. The paths of
comets on the other hand are usually _very_ oval; so that in their
courses many of them pass out as far as the known limits of the solar
system, and even far beyond. It should be mentioned that nowadays the
tendency is to consider comets as permanent members of the system,
though this was formerly not by any means an article of faith with
astronomers.

Meteors are very small bodies, as a rule perhaps no larger than pebbles,
which move about unseen in space, and of which we do not become aware
until they arrive very close to the earth. They are then made visible to
us for a moment or two in consequence of being heated to a white heat by
the friction of rushing through the atmosphere, and are thus usually
turned into ashes and vapour long before they reach the surface of our
globe. Though occasionally a meteoric body survives the fiery ordeal,
and reaches the earth more or