1770, which passed through the system of Jupiter's satellites without affecting their orbits (this theory has been since published in the Annals of the Academy of Sciences, vol. iii.); and also a memoir on Faye's periodical comet of 1743, which, according to his prediction, returned to its perihelion on the 4th April, 1851, and on the 12th September, 1858. The next inquiry of our author was into the perturbations of the planet Uranus, which had baffled the ingenuity of astronomers. His first memoir on the theory of this planet was published in November, 1845, and was so highly esteemed that its author, on the 19th January, 1846, was elected a member of the Academy of Sciences, in the section of Astronomy, in place of Count Cassini. In June, 1846, M. Leverrier published his second memoir on the motions of Uranus, in which he shows that its irregularities cannot be produced by Jupiter or Saturn, but must be owing to the action of an undiscovered planet, "situated in the ecliptic at a mean distance double that of Uranus;" and he decides that its heliocentric place in January 1, 1847, must be in 325° of longitude. In a subsequent memoir, published on the 31st August of the same year, he determines its mass and all the elements of its orbit, placing it in 318° 47´ of longitude, about 5° to the east of the star δ of Capricorn, and adding that at its opposition on the 19th August, 1846, its disc being about 3´´7, it would be visible with good telescopes. This position of the unknown planet was communicated on the 18th September to M. Galle of Berlin, who discovered it as a star of the eighth magnitude on the 23rd September, the same evening on which he received its position from M. Leverrier. This grand discovery placed M. Leverrier in the first rank of European mathematicians, and honours of all kinds were conferred upon him from every part of Europe. Louis Philippe gave him the cross of officer of the legion of honour, of which he has since been made commander. The king of Denmark sent him the order of Dannebroga. Foreign academies elected him one of their honorary or corresponding members. M. Salvandi, the minister of public instruction, had a bust of him executed. A professorship of astronomy was added to the Faculty of Sciences in Paris, as an appointment for the great astronomer; and he was made a member of the Board of Longitude as adjunct astronomer.
Previous to his great work on the theory of Uranus, namely in 1843, M. Leverrier had presented to the Academy of Sciences his "New determination of the Orbit of Mercury and its perturbations;" and in 1843 he communicated the new tables of Mercury founded on his theory, which have been since published in 1860, in the fifth volume of the Annals of the Imperial Observatory of Paris. In 1853 he communicated to the Academy his tables of the apparent motion of the Sun, which were published in the same work; and so great is the accuracy of these tables and those of Mercury, that the observed egress of Mercury from the Sun's disc on the morning of the 12th of November, 1861, differed only one second from the mean of the observations made at Rome, Altona, and Malta. In 1853, on the death of M. Arago, M. Leverrier was appointed director of the imperial observatory; and the results of the great reforms which he made in that establishment appeared in 1855 and 1856, in the two volumes of the Annals of the Observatory, which were published in these years. The third and fourth volumes of this important work were published in 1858, the fifth volume in 1859, the two parts of the sixth volume in 1860, and the four volumes for 1856-57-58 and 1859 in October, 1861.
In 1855 M. Leverrier called the attention of the Academy of Sciences to the great importance of meteorological observations, and at the same time addressed to the ministers of war and public instruction a plan for organizing them. Both these ministers instantly adopted the plan, and measures were taken "for establishing meteorological observations at Paris, in France, and in the French colonies, on the largest scale." A magnetical and meteorological observatory was established at Algiers, M. Leverrier having, at his own risk, had all the instruments prepared which such an institution required. On the 2nd January, 1860, M. Leverrier communicated to the Academy a remarkable paper on the theory of Mercury. He found that the observations made on twenty-one transits of that planet, could be represented within nearly a second by augmenting by thirty-eight seconds the secular motion of its perihelion. He conceives that this excess of motion is due to some unknown cause, which must be such as not to produce any other sensible effect on the planetary system. This cause, he thought, might be either a single planet between Mercury and the Sun, or a ring of asteroids such as that which exists between Mars and Jupiter. If the disturbing body were a single planet, its brightness, he thought, must be such as to make it visible, and therefore he is disposed to believe that the increased secular motion in Mercury's perihelion is produced by a ring of asteroids, which, if they exist, we fear we have no chance with our present telescopes of discovering. On the 3rd of June, 1861, M. Leverrier communicated to the Academy of Sciences a letter, addressed to Marechal Vaillant, "On the Constitution of the Planetary System, and on the theory and tables of Mars," which he had completed, and which no doubt will appear in the next volume of the Annals of the Observatory. The following are the results at which he has arrived:—1. That there is between Mars and the Sun a ring of asteroids, whose united mass is comparable to that of Mercury. 2. That at the distance of the Earth from the Sun there is a second ring of asteroids, whose mass is nearly equal to the tenth part of that of the Earth. 3. That the united mass of the asteroids between Mars and Jupiter, is nearly equal to the third part of the mass of the Earth. 4. That the masses of the two last groups are complementary to each other. Ten times the mass of the group placed at the distance of the Earth, added to three times the united mass of the seventy asteroids between Mars and Jupiter, is nearly equal to the mass of the Earth. These remarkable deductions will, no doubt, excite some controversy in the astronomical world. On the 2nd December, 1861, M. Leverrier laid before the Academy of Sciences an abstract of his researches on "The System of Planets nearest the Sun, Mercury, Venus, the Earth, and Mars," and on the three rings of asteroids. In this communication he insists more particularly on the theories and the observations which support them, and promises, at one of the next meetings of the Academy, to treat of the comparison of the theories with observation. Like his eminent predecessor, M. Arago, M. Leverrier occupies a high place in the political world. In 1849 he represented the department of La Manche in the legislative assembly, joining the anti-revolutionary party, and taking a deep interest in all questions of public instruction or scientific interest. In 1859 he drew up a report on the project of a law relative to the construction of new lines of the electric telegraph. He took an active part also in the measures for reorganizing the polytechnic school, and he was a member of the commission for drawing up a scheme for professional education. M. Leverrier speaks with great facility and distinctness, and from his special knowledge on many subjects he has much influence in the chamber. When political parties were greatly divided, M. Leverrier attached himself to the politics of the Court. After the coup d'état he was appointed a member of the senate, and was afterwards inspector-general of superior instruction. From this time he devoted himself to the improvement of educational institutions in France, and he especially impressed upon the study of the sciences a more practical and limited character. In 1850 he drew up a report on the system of instruction in the polytechnic school, and in 1854 he was appointed a member of the commission for improving it. The great services which M. Leverrier has done to astronomy, and his capacity for doing more, induce us to express the hope that he will devote the whole of his leisure to physical astronomy, and place himself, as no doubt he will do, at the head of the astronomers of any age or nation.—D. B.
LEVESQUE, Pierre Charles, a French historian, born at Paris 28th March, 1736; died 12th May, 1812. In 1773 he went to Russia, and was appointed professor in the school of cadet nobles at St. Petersburg. From the documents of the kingdom he compiled a valuable "History of Russia." He followed this by a "History of France under the first five Valois;" and by histories of Rome and Greece.—P. E. D.
LEVI, David, by birth a Jew, a native of London, where he was born in 1740 in humble circumstances. He was brought up to the trade of a shoemaker, which he exchanged for that of a hatter, but contrived to acquire a superior knowledge of the Hebrew language and some reputation as a writer. In 1783 he published "An Account of the Rites and Ceremonies of the Jews," in an octavo volume, which was followed by his "Lingua Sacra," consisting of a Hebrew Grammar, a Hebrew-English Dictionary, &c., the first part of which appeared in 1785, and the last in 1788. This work must be regarded a remarkable monument of industry and perseverance, produced as it was in the leisure hours of a life of labour and poverty; but it is of no
