These important communications were made to the French Academy of Sciences on the 31st of August, 1846. On the 18th of the following month, M. Leverrier wrote to his friend, M. Galle, of Berlin, requesting him to direct his telescope to that point in the heavens which his computations had revealed as the one occupied by the constructive planet. The request was readily complied with, and on the very first evening of examination, a star of the eighth magnitude was discovered, which was evidently a stranger in that region, as it was not found on an accurate map of the heavens, including all stars of that magnitude. The following evening was awaited with the deepest interest, to decide, by the actual motion of the suspected star, whether indeed it was the planet so wonderfully revealed by the analysis of Leverrier. The night came on. Again was the telescope directed to the star in question, when lo! it had moved from its former place, in a direction and with a velocity almost precisely accordant with the theory of the French geometer! The triumph was perfect; the planet was actually found. The news of its discovery flew in every direction, and filled the world with astonishment and admiration.

The exceeding accuracy with which its place had been predicted, coming within less than one degree of its actual position, gave to M. Leverrier the highest confidence in the perfection of his analysis, and filled with astonishment the oldest and most learned astronomers. If scepticism had existed with reference to the possible solution of so complex a problem,-if the theory of Leverrier had been regarded as a beautiful speculation, ingenious and plausible, but vain in its practical application, the actual discovery of the planet silenced all cavil, and put to flight every lingering doubt.

As if anything were wanting to give a more positive character to the computations of Leverrier, it was now found that a young English mathematician, Mr. Adams, of Cambridge, had actually accomplished the resclution of precisely the same problem, and had reached results almost identical with those of the French geometer. This astonishing coincidence on the part of two computers unknown to each other, each starting from the same data, pursuing independent trains of reasoning, and arriving at the same results, confirmed, as it would seem, in the fullest manner, the accuracy of the resolution which had been obtained.

On learning that Leverrier had communicated to the Academy of Sciences, in August, 1846, his final results, I wrote immediately,

requesting the computed place of his planet, with such directions as would best guide me in a search, which I desired to make for it with the great refracting telescope of the Cincinnati Observatory. But before my letter reached its destination, the planet had been found, and the news of its discovery soon reached the United States. It was almost impossible for me to credit the statement, and I was almost disposed to believe that the prediction of the planet's position had been mistaken for its actual discovery. With these conflicting doubts, I waited for the coming of night with a degree of anxiety and excitement which may be readily imagined. I had no star-chart to guide me in my search for the planet; I had no meridian instrument with which to detect it by its motion; but I was not without hope that the power of our great telescope might be sufficient to select at once the planet from among the fixed stars, by the magnitude of its disc.

As soon as the twilight disappeared, the instrument was directed to the point in the heavens where the planet had been found. I took my place at the finder, or small telescope attached to the larger one, and my assistant was seated at the great instrument.

On placing my eye to the finder, four stars of the eighth magnitude occupied its field. One of them was brought into the field of the large telescope, and critically examined by my assistant, and rejected. A second star was in like manner examined, and rejected. A third star, rather smaller and whiter than either of the others, was now brought to the centre of the field of the great telescope, when my assistant exclaimed, "There it is! there is the planet! with a disc as round, bright, and beautiful as that of Jupiter!" There, indeed, was the planet, throwing its light back to us from the enormous distance of more than 3,000,000,000 of miles, and yet so clear and distinct, that in a few minutes its diameter was measured, and its magnitude computed.

It is not my intention to follow, critically, the history of this wonderful discovery; yet there are some facts so remarkable, that it would be wrong to pass them in silence. From the moment the planet was detected in Berlin, it has been observed by all the best instruments in the world, with a view of ascertaining how accurately theory had assigned the elements of its orbit. In consequence of its very slow motion, it became a matter of the utmost importance to obtain, if possible, some

remote observation made by an astronomer who might have entered the place of the planet in his catalogue as a fixed star. Mr. Adams led the way in the computation of the elements of the orbit of the new planet from actual observation, and was followed by many other computers,-among them Mr. S. C. Walker, then of the Washington Observatory, United States.

Having obtained an approximate orbit, Mr. Walker computed backwards the places of the new planet for more than fifty years

and then examined the late catalogues, in the hope of finding its place on some of them as a fixed star. Among recent catalogues there was no success; but in an examination of Lalande's Catalogue, he found an observation on a star of the eighth magnitude, made May 10th, 1795, which was so near the place which his computation assigned the planet at the same date, that he was led to suspect that this star might indeed prove to be the new planet. In case his conjecture were true, on turning the telescope to the place occupied by the star, it would be found blank, as its planetary motion would have removed it very far from the place which it occupied more than fifty years before. The experiment having been made, no star could be found; and strong evidence was thus presented that Mr. Walker had actually found an observation of the new planet, giving its position but in consequence of the great discrepancy between

in 1795;

L

the period of M. Leverrier and that which would result from a reliance on this observation of the new planet Neptune, Mr. Walker's discovery was at first received with great hesitation. A greater doubt was thrown over the matter from the fact that Lalande had marked the observation as uncertain; and it was only by reference to the original manuscripts preserved in the Royal Observatory of Paris that the doubts could be removed.

The discovery of Mr. Walker was subsequently made by Mr. Petersen, of Altona; and the results of these astronomers reached Paris on the same day. A committee was at once appointed to examine the original manuscript of Lalande, when a most remarkable discovery was made. This astronomer had observed a star of the eighth magnitude on the evening of the 8th of May, 1795; and on the evening of the 10th, not finding the stai as laid down, but observing one of the same magnitude very near the former place, he rejects the observation of the 8th of May as inaccurate, and enters the observation of the 10th, marking it doubtful.

On close examination, this star proves to be the planet Neptune; and by this discovery we are placed in possession of observations which render it possible to determine the elliptic elements of the new planet with great precision. These differ so greatly from those announced by Leverrier and Adams previous to the discovery, that Professor Pierce, of Cambridge, Massachusetts, pronounces it impossible so to extend fairly the limits of Leverrier's analysis as to embrace the planet Neptune; and that, although its mass, as determined from the elongation of its satellite, renders it possible to account for all the perturbations of Uranus by its action, in the most surprising manner, yet, in the opinion of Professor Pierce, it is not the planet to which geometrical analysis directed the telescope. Leverrier rejects absolutely the result reached by the American geometer, and claims Neptune to be the planet of his theory, in the strictest and most legitimate sense.

Time and observation will settle the differences of these distinguished geometers; and truth being the grand object of all research, its discovery will be hailed with equal enthusiasm by both of the disputants. In any event, the profound analytic research of Leverrier is an ever-during monument to his genius, and his name is for ever associated with the most wonderful discovery that ever marked the career of astronomical science.

THE wonderful characteristics which mark the flight of comets through space; the suddenness with which they blaze forth; their exceeding velocity, and their terrific appearance; their eccentric motions, sweeping towards the sun from all regions and in all directions; have rendered these bodies objects of terror and dread in all ages of the world. While the planets pursue an undeviating course round the sun, in its orbits nearly circular, and almost coincident with the plane of the earth's