ous planets are discovered, and that, not as
was recently predicted, in numbers gradually decreasing, but so rapidly
that more have been discovered during the last ten years than during the
preceding twenty.

The discovery of the giant planet Uranus, an orb exceeding our earth
twelve and a half times in mass and seventy-four times in volume, was a
matter of much greater importance, so far as the dignity of the
planetary system was concerned, for it is known that the whole ring of
asteroids together does not equal one-tenth part of the earth in mass,
while Uranus exceeds many times in volume the entire family of
terrestrial planets--Mercury, Venus, the Earth, and Mars. The detection
of Uranus, unlike that of Ceres, was effected by accident. Sir W.
Herschel was looking for double stars of a particular kind in the
constellation Gemini when by good fortune the stranger was observed.

The interest with which astronomers received the announcement of the
discovery of Uranus, though great, was not to be compared with that with
which they deservedly welcomed the discovery of Neptune, a larger and
more massive planet, revolving at a distance one-half greater even than
the mighty space which separates Uranus from the sun, a space so great
that by comparison with it the range of 184,000,000 of miles, which
forms the diameter of our earth's orbit, seems quite insignificant. It
was not, however, the vastness of Neptune's mass or volume, or the awful
remoteness of the path along which he pursues his gloomy course, which
attracted the interest of astronomers, but the strangeness of the
circumstances under which the planet had been detected. His influence
had been felt for many years before astronomers thought of looking for
him, and even when the idea had occurred to one or two, it was
considered, and that, too, by an astronomer as deservedly eminent as Sir
G. Airy, too chimerical to be reasonably entertained. All the world now
knows how Leverrier, the greatest living master of physical astronomy,
and Adams, then scarce known outside Cambridge, both conceived the idea
of finding the planet, not by the simple method of looking for it with a
telescope, but by the mathematical analysis of the planet's disturbing
influence upon known members of the solar system. All know, too, that
these mathematicians succeeded in their calculations, and that the
planet was found in the very region and close to the very point
indicated first by Adams, an