pear more wild and chimerical. To cominence a prolonged research for an invisible world, one that no keenness of vision could detect, and which never could be revealed but by telescopic aid, a world whose magnitude was so small that it would not appear so large as a star of the smallest size visible to the naked eye, and one which must be sought out and detected, not by its planetary disc, but by its wanderings among thousands of stars, which it in all respects resembled, and from which it could in no wise be distinguished, but by its motion, seemed like a wasting of time and utter throwing away of labor and energy.

Piazzi, of Palermo, in Sicily, was one of the planet searching association. He had already distinguished himself as an eminent and accurate observer, and had with indefatigable zeal constructed a most extensive catalogue of the relative places of the fixed stars, and thus, in some sense, anticipated a part of the labor that the research for the suspected planet contemplated. Assisted by his own and by preceding catalogues, he entered on the great work with the energy and zeal which distinguished all his great astronomical efforts. On the evening of the first day of the year 1801, this astronomer had his attention attracted by a small star in the constellation of the Bull, which he took to be one recorded in the catalogue of Mayer; but on examination, it was found not to occupy any place either on Mayer's or his own catalogue. Yet it was so small that it was an easy matter to account for this fact, by its having been overlooked in preceding explorations of the region in which it was found. With intense anxiety the astronomer awaited the evening of the following night, to settle the great

but years of persevering toil could have wiped away the reproach which rested on astronomy.

A sufficient number of observations were soon made to reveal the orbitual elements of the planet, now named Ceres. It was found, in all respects, to narmonize in its movements with the older planets, and its orbit filled precisely the blank in the strange empirical law discovered by Bode. The period and distance hypothetically computed from that law sixteen years before, by Baron de Zach, were verified in the most remarkable manner by the actual period and distance of Ceres. Order and beauty now reigned in the planetary system, and a most signal victory had crowned the efforts of astronomical science.

The only remarkable difference between the new planet and the old ones, consisted in its minute size, the great obliquity of its orbit, and the dense atmosphere by which it appears to be surrounded. Its diameter is so small as to render its measure next to impossible, and the best practical astronomers differ widely in their results. Sir William Herschel makes its diameter only 163 miles, while Schroeter cannot make it less than ten times that quantity. The mean of these two extremes is probably near the truth.— No satellites have been found in attendance on this minute planet, although Sir William Herschel suspected the existence of two at one time, a suspicion which subsequent observations have not confirmed.

The beautiful order established in the solar system by the discovery of Ceres was a subject of the highest gratification to the whole astronomical world, and especially to those who had been instrumental in reaching this remarkable result. An opportunity had

scarcely presented itself for the expression of delight occasioned by this announcement, before all interested were startled by a declaration from Dr. Olbers, of Bremen, that he had found another planet on the evening of the 28th of March, 1802, with a mean distance and periodic time almost identical with those of Ceres. This discovery broke through all the analo gies of the solar system, and presented the wonderful anomaly of two planets revolving in such close proximity, that their orbits, projected on the plane of the ecliptic, actually intersected each other.

The new planet was called Pallas, and is of a magnitude about equal to that of Ceres. Its orbit is greatly inclined to the plane of the ecliptic, and its eccentricity is very considerable. The existence of these small planets, in such near proximity, for a long while perplexed astronomers. At length Olbers suggested that these minute bodies might be the fragments of a great world, rent asunder by some internal convulsion of sufficient power to produce the terrific result, but of a nature entirely beyond the boundary of conjecture.

Extraordinary as this hypothesis may appear, the results to which it led are not less remarkable. If a world of large size had been actually burst into fragments, it is easy to perceive that these fragments, all darting away in the orbits due to their impulsive forces. would start from the same point, and hence would return at different intervals indeed, but would all again pass through the point of space occupied by the parent orb when the convulsion occurred. Hav. ing found two of these fragmentary worlds, the point of intersection of their orbits would indicate the re

on through which the other fragments might be expected to pass, and in which they might possibly be discovered. So reasonable did the views of Olbers appear, that his suggestions were immediately acted upon by himself and several distinguished observers, and on the 2d of September, 1804, Mr. Harding, of Lilienthal, while scrutinizing the very region indicated by Olbers, detected a star of the eighth magnitude, which seemed to be a stranger, and was soon recognized to be another small planet, fully agreeing, in all its essential characteristics, with the theory of Olbers. The new world was named Juno, and is remarkable for the eccentricity of its orbit. Its diameter has not been well determined, owing to its minute size. This discovery gave to the theory of Olbers the air of reality, and finding the nodes of the three fragments to lie in the opposite constellations Cetus and Virgo, he prosecuted his researches in these regions with redoubled energy and zeal.

His efforts were not long without their reward. On the 29th of March, 1807, he detected the fourth of his fragments in the constellation Virgo, and very near the point through which he had, for four years, been waiting to see it pass. This was a most wonderful discovery, and almost fixed the stamp of truth upon the most extraordinary theory which had ever been promulgated. This new asteroid was named Vesta and for nearly forty years, the examinations which were conducted revealed no new fragment, and it began to be regarded as positively ascertained, that all the small bodies revolving in this region had been revealed to the eye.

But on the 8th day of Dec., 1845, Mr. Hencke, of

Dreisen announced to the world the discovery of an other asteroid, which was named Astrea. Before two years had rolled round, the same indefatigable observer discovered a sixth member in this wonderful group, which was called Hebe. His success induced other observers to undertake a similar examination, and in a very short time the researches of Mr. Hind of London, were rewarded by the discovery of a seventh and eighth asteroid, which were named Iris and Flora.

Thus have we no less than eight of these minute worlds, revolving in orbits so nearly equal, that for weeks and months these miniature orbs may sweep along in space, almost within hail of each other. Let us now return to an examination of the hypothesis of Olbers, that these are the fragments of a world of large size, which once occupied an orbit intermediate between those of Mars and Jupiter.

The

If any internal convulsion could burst a world and separate its fragments, it is readily seen that the fragments of largest mass would move in orbits more nearly coincident with that of the original planet, while the smaller fragments would revolve in orbits greatly inclined to the primitive one. This condition is wonderfully fulfilled among the asteroids. larger planets, Ceres and Vesta, revolve in orbits with small inclinations to the ecliptic, while the smaller objects are in some instances found to move in planes with very great inclinations. The force necessary to burst a planet, and to give to its fragments certain orbits, has been computed by Lagrange, and he finds that in case any fragment is projected with an initial velocity one hundred and twenty-one