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. MAGNITUDE OF COMETS. Although Comets have a smaller mass than any other cosmical bodies--being, according to our present knowledge, probably not equal to 1/5000th part of the earth’s mass--yet they occupy the largest space, as their tails in several instances extend over many millions of miles. The cone of luminous vapour which radiates from them has been found in some cases (as in 1680 and 1811) equal to the length of the earth’s distance from the sun, forming a line that intersects both the orbits of Venus and Mercury. It is even probable that the vapour of the tails of comets mingled with our atmosphere in the years 1819 and 1823.--_Humboldt’s Cosmos_, vol. i. COMETS VISIBLE IN SUNSHINE--THE GREAT COMET OF 1843.