we pray may extend to all evangelical churches, it will utterly melt away every bar of prejudice which has too long separated one communion from another; and theological truth will be sought for its own sake, without respect to the denominational channel in which it may chance to flow.

ART. V.-1. Recherches sur les Mouvements d'Uranus. Par M. U. J. LE VERRIER. Séance de l'Académie des Sciences du 1er. Juin, 1846. Comptes Rendus, tome xxii, No. 22. 2. Sur la Planète qui Produit les Anomalies Observées dans le Mouvement d'Uranus. Détermination de sa Masse, de son Orbite, et de sa Position Actuelle. Par M. U. J. LE VERRIER. Séance de l'Académie des Sciences du 31 Août, 1846. Comptes Rendus, tome xxiii, No. 9.

3. Examen des Remarques Critiques, et des Questions de Priorité que la Découverte de M. Le Verrier a Soulevées. Par M. ARAGO. Séance de l'Académie des Sciences du 19 Octobre, 1846. Comptes Rendus, tome xxiii, No. 16.

4. Account of some Circumstances historically connected with the Discovery of the Planet exterior to Uranus. By G. B. AIRY, Esq., Astronomer Royal. London, Edinburgh, and Dublin Philosophical Magazine, and Journal of Science. Dec., 1846 LE VERRIER's idea of sitting down in his study to discover a new planet by ciphering, instead of resorting to the vulgar method of looking after the suspected stranger with a telescope, was bold and original. We believe his investigation to be the first recorded and published attempt to demonstrate the existence and whereabout of a member of the solar family, without the aid of hypothesis of any kind, by a rigorous application of the law of universal gravitation. The successful result of his labors, attained with arduous toil in the most abstruse regions of analysis, has already been announced to the world; and while it has struck the unlearned with a species of vague astonishment, it has been hailed by those who could better comprehend the magnitude, and appreciate the difficulties, of the undertaking, with an admiration which borders upon enthusiasm. As a triumph of mathematical skill, his work surpasses all former achievements in theoretical astronomy, and inscribes the name of Le Verrier in living characters on the furthest boundary of our system. What future revelations a long series of observations upon the motion of the new planet may make, it

would now be presumption to predict; but it is not difficult to conjecture that many years must elapse before the limits of the sun's dominion can be extended further into space.

We have said that Le Verrier's method of research was original. A short sketch of the history of the discovery of the telescopic planets will establish the truth of this allegation.

In 1781 Sir William Herschel was engaged in a series of observations for the purpose of determining the parallax of the fixed stars. On the 13th of March of that year he observed a star with a sensible disc, which was magnified under the higher powers of his telescope. The body, therefore, could not be a fixed star. He suspected it to be a comet; and, after watching its course till the 19th of the following month, he reported it as such to the Royal Society. Subsequent observations of the continental astronomers proved the supposed comet to be a planet, which revolved around the sun in the regions of space far beyond the orbit of Saturn. These facts prove the justice of Arago's remark, that the discovery of Uranus was neither the consequence of a preconceived idea, nor of a systematic combination of observations.

John Kepler had observed a void space (hiatus) between the orbits of Mars and Jupiter, and imagined that the harmony of the solar system required that this space should be occupied by a planet. It had been suggested as early as 1772 that if the distance of Mercury from the sun be represented by 4, the distance of Venus will be 3+4; of the Earth, 6+4; of Mars, 12+4; of Kepler's hypothetical planet, 24+4; of Jupiter, 48+4; of Saturn, 96+4. This series constitutes what is usually called Bode's law. The discovery of Uranus, at a distance corresponding to 192+4, the next term of the series, seemed to give the law so strong confirmation, that astronomers were encouraged to hope that the missing planet between the orbits of Mars and Jupiter might be discovered. Schroeter formed an association of twenty-four German astronomers to make a systematic search for the planet, but their search was fruitless. De Zach even computed, on the basis of Bode's law, what should be the elements of the orbit of the supposed planet; but his calculations did not determine its place in the heavens. His researches, though worthy of a place in the history of astronomy, were founded entirely on the analogies of the solar system, and, on this account, cannot be placed in comparison with the rigorous demonstration of Le Verrier, of which the basis was an established and universally admitted truth.

After all these conjectures, computations, and researches, the discovery of Ceres was the result of accident. Piazzi, the astro

nomer royal at Palermo, being engaged in a review of the heavens for the purpose of forming a new catalogue of the fixed stars, perceived a small body, which a few days afterward appeared to have changed its position. This discovery was made on the 1st of January, 1801. Piazzi believed the body to be a comet, and sent an account of his observations to Bode. An inspection of these observations convinced Bode that the body was a planet, and his conjecture was verified soon after by Piazzi himself. It is remarkable, that the mean distance and periodic time of Ceres corresponded very nearly with the same elements of the hypothetical planet, as calculated by De Zach.

Ceres filled up the gap which Kepler had noticed in the planetary spaces, and supplied the term wanting in Bode's law. The harmony of the system was complete, Bode's law was satisfied, and there was no reason to anticipate the discovery of another planet. But science breaks through the trammels of hypothesis, and the generalization of to-day falls before the fact of to-morrow. On the 28th of March, 1802, Olbers, of Bremen, while examining the constellation Virgo, observed a movable star of the seventh magnitude, which was soon afterward proved by Gauss to be a planet, and was named Pallas.

The advent of the goddess of wisdom to claim a place among the planets was as unexpected as when, according to the fable, she sprang forth armed and full grown from the brain of Jupiter. If Ceres had been wanting to make perfect the heavenly harmonies, Pallas was now leered at as an interloper, who was sure to introduce discord into the celestial chorus. A lucky suggestion of Olbers saved the music of the spheres. He remarked, that though the orbit of Pallas had a much greater inclination and eccentricity than that of Ceres, the mean distances of the two planets from the sun were very nearly equal. He observed also that their orbits appeared to intersect each other in two points, one of which was in Virgo and the other in Cetus. He was thus led to make the fortunate conjecture that Ceres and Pallas were fragments of a larger planet, which had been broken in pieces by some external shock or internal explosion. He also suggested that other fragments of the shattered planet probably existed, which, in process of time, would likewise pass through the nodes of the orbits of Ceres and Pallas.

This singular but ingenious hypothesis was destined soon to receive an unexpected confirmation. While Harding of Lilienthal was exploring the firmament for the purpose of constructing some celestial charts, he discovered, Sept. 2d, 1804, another planet near

one of the nodes of the orbits of Ceres and Pallas. Though the discovery of Juno was accidental, it encouraged Olbers to hope that, by watching the region of these nodes, other fragments of the ancient planet might be discovered. Accordingly, he undertook to review the stars in Virgo and Cetus several times each year, particularly at their oppositions, when the planetary fragments, if any existed, would be nearest to the earth, and, consequently, most likely to be detected. After three years of persevering labor, his efforts were rewarded by the discovery of Vesta.

This was the first instance in the history of astronomy, of the discovery of a suspected planet by a systematic series of observations. But, as Arago justly remarks, the supposition of Olbers, that if a planet existed, it would pass, at some time or other, through a given constellation of the zodiac, bore neither resemblance nor analogy to the demonstration of Le Verrier, that a planet necessarily existed beyond Uranus, in a determinate direction, at a determinate distance, and with a determinate mass.

This interesting group of planets received no further accession to its numbers till the 8th of Dec., 1845. On that day, Hencke of Driessen, while studying the constellation Taurus, discovered a star of the ninth magnitude in a place where none had been seen before. Six days afterward it was again observed by Encke of Berlin, who established its planetary character, and named it Astræa.

It thus appears that of the six planets whose existence was detected from 1781 to 1845, five were discovered by fortunate accidents, and one by following the suggestions of a fanciful but specious hypothesis. It was reserved for Le Verrier, in 1846, to introduce a new era in physical astronomy by applying the powers of the higher mathematics to enlarge the boundaries of the solar system.

We next propose to give an account of this wonderful discovery, and have collected for this purpose the principal facts in relation to it from the scientific papers cited above. We shall endeavor to present these facts in a less abstruse and technical garb than they wear in the original documents.

The illustrious astronomer, John Kepler, discovered that the planets revolve in ellipses, having the sun in one of their foci; and that the arcas described by the radius vectors are proportional to the times. If the sun were attended by only one planet, these laws of Kepler would be rigorously true; but it is a necessary consequence of Newton's law of universal attraction, that if two or more planets revolve around the sun, they will attract each other

in the direct ratio of their masses, and in the inverse ratio of the squares of their distances. These mutual attractions among the planets cause them to deviate very sensibly from their elliptic orbits, and produce irregularities in their motion, which are called perturbations. It is possible to ascertain the effect of the disturbing force of a given planet upon each of the others in the system, and the sum of the perturbations produced by all the planets in the motions of any one, will give the amount of the deviations of that one from its elliptic orbit. These corrections will give the planet's theoretical orbit; and when, after a series of years, the observed place of the body is constantly found to agree with its calculated, or theoretic place, the motions of the planet are known, and its orbit represents the observations.

After La Place had developed analytically the perturbations produced upon Uranus by Jupiter and Saturn, it was hoped that exact tables of the motion of Uranus could be constructed. This work was undertaken by Bouvard; but he met with unexpected difficulties.

Between the years 1690 and 1771, Uranus had been observed, as a fixed star of the sixth magnitude, by Flamstead, Bradley, Mayer, and Lemonnier, no less than seventeen times. Regular meridian observations of Uranus had been made for nearly forty years from the date of its discovery by Herschel, when, in 1820, Bouvard commenced the construction of his tables. But Bouvard found it impossible to represent, at the same time, the ancient and the modern observations. He therefore rejected those made prior to 1781, and calculated his tables on the basis of those made since that date, which he presumed were entitled to greater confidence. He proposed to leave it for future times to determine whether the difficulty of reconciling the two series of observations was caused by the inaccuracies of the ancient series, or resulted from some foreign and undiscovered action which might affect the planet.

But in 1845, Bouvard's tables, which failed to represent the old observations, were equally in error in respect to the actual place of Uranus. Thus Uranus alone, of all the planets, refused to be restrained by the curb and rein of theory. The obstinate old deity seemed inclined to have his own way, and move along any path he pleased, in provoking disregard of the metes and bounds which the presumptuous children of this puny grand-daughter of his had prescribed for him. What was to be done? The wayward progenitor of the gods must not be allowed to set bad examples to his descendants, and introduce disorder into a household where everything had gone on, hitherto, as regularly as clock-work.