This noble discovery marked in a signal manner the maturity of
astronomical science. The proof, or at least the urgent presumption,
of the existence of such a planet, as a means of accounting (by its
attraction) for certain small irregularities observed in the motions
of Uranus, was afforded almost simultaneously by the independent
researches of two geometers, Mr. Adams of Cambridge, and M. Leverrier
of Paris, who were enabled _from theory alone_ to calculate whereabouts
it ought to appear in the heavens, _if visible_, the places thus
independently calculated agreeing surprisingly. _Within a single
degree_ of the place assigned by M. Leverrier’s calculations, and by
him communicated to Dr. Galle of the Royal Observatory at Berlin, it
was actually found by that astronomer on the very first night after
the receipt of that communication, on turning a telescope on the spot,
and comparing the stars in its immediate neighbourhood with those
previously laid down in one of the zodiacal charts. This remarkable
verification of an indication so extraordinary took place on the 23d of
September 1846.[20]--_Sir John Herschel’s Outlines._
Neptune revolves round the sun in about 172 years, at a mean distance
of thirty,--that of Uranus being nineteen, and that of the earth one:
and by its discovery the solar system has been extended _one thousand
millions of miles_ beyond its former limit.
Neptune is suspected to have a ring, but the suspicion has not been
confirmed. It has been demonstrated by the observations of Mr. Lassell,
M. Otto Struve, and Mr. Bond, to be attended by at least one satellite.
One of the most curious facts brought to light by the discovery of
Neptune, is the failure of Bode’s law to give an approximation to its
distance from the sun; a striking exemplification of the danger of
trusting to the universal applicability of an empirical law. After
standing the severe test which led to the discovery of the asteroids,
it seemed almost contrary to the laws of probability that the discovery
of another member of the planetary system should prove its failure as
an universal rule.