hematical demonstration is not
sufficient (or perhaps we may say it is too much) for some minds.
Therefore, to simplify matters, Venus has been provided with a mirror
surface and a glass case. (See preceding essay, on Astronomical
Paradoxes, for further details.)

The enigma next to be considered is of a more doubtful character than
the myth relating to the satellite of Venus. Astronomers are pretty well
agreed that Venus has no moon, but many, including some deservedly
eminent, retain full belief in the story of the planet Vulcan.

More than seventeen years ago the astronomical world was startled by the
announcement that a new planet had been discovered, under circumstances
unlike any which had heretofore attended the discovery of fresh members
of the solar system. At that time astronomers had already become
accustomed to the discovery, year after year, of several asteroids,
which are in reality planets, though small ones. In fact, no less than
fifty-six of these bodies were then known, whereof fifty-one had been
discovered during the years 1847-1858 inclusive, not one of these years
having passed without the detection of an asteroid. But all these
planets belonged to one family, and as there was every reason to believe
that thousands more travel in the same region of the solar system, the
detection of a few more among the number had no longer any special
interest for astronomers. The discovery of the first known member of the
family had indeed been full of interest, and had worthily inaugurated
the present century, on the first day of which it was made. For it had
been effected in pursuance of a set scheme, and astronomers had almost
given up all hopes of success in that scheme when Piazzi announced his
detection of little Ceres. Again the discovery of the next few members
of the family had been interesting as revealing the existence of a new
order of bodies in the solar system. No one had suspected the
possibility that besides the large bodies which travel round the sun,
either singly or attended by subordinate families of moons, there might
be a ring of many planets. This was what the discovery of Ceres, Pallas,
Juno, and Vesta seemed to suggest, unless--still stranger thought--these
were but fragments of a mighty planet which had been shattered in
long-past ages by some tremendous explosion. Since then, however, this
startling theory has been (itself) exploded. Year after year new members
of the ring of multitudin