Page:The New International Encyclopædia 1st ed. v. 12.djvu/188

After his return to France lie taught at Toulouse, Besancon, and N'aney. He was appointed to the chair of l^atin and Greek philosophy at the Col- lege of France in lS5(i, and liecame a iiieinl)er of the Institute in 1805, and vice-president of the Aeadi'niie des Sciences Alorales et I'olitiques in 187.'!. In philosophy he was a pupil of I'ousin. His works include: La plii/si(iiii' d'Aiislntc et la science contcmporaine (1800) : La science dii beau, ses principes, scs applicitiions, son histoirc (1872) ; Etudes de pitilosophie grccqne et latine (1864); Le spirit iuilism<: dans I'art (1804); La science de I'incisible (1865) ; and I^es har- monies provident ielles (1872; 4th ed. 1885). LEVER (OF. lercor, Icveiir, Ft. leveur, lever, from Lat. levator, lifter, from levarc. to raise). A form of machine much useil in simple physical instruments. It consists essentially of a rigid body pivoted at one point. If tlie lindy is acted on by two forces ( F, and F,) in ditrerent direc- tions, which hold it in equilibrium, the formula for the mechanical advantage can l)e deduced at once; the general principle being that since there I •<- / is equilibrium the moment of one force around the pivot at P, i. e. F,/,, must equal the moment of the second force around the same axis, i.e. FjL. The lixeii point is called the "fulcrum.' and i, and /^ the 'lever-arms.' Thus to balance a force F, a force l'"2 is necessary, where F,/, = F,L, The 'mechanical advanUige' is therefore, /,//,. Another mode of deducing the same formula is to consider the system displaced slightly when in equilibrium under the forces F, and F.. The point of application of F, will move a distance x; that of F,, a distance x,. By the principle of energy F,a;,=Fja;2; but by geometry, if the displacement is small, -l-=---?,and hence FJ,=: FjJj, as l)efore. In some levers the fulcrum lies between the two balancing forces, e.g. pump-handle, crow- bar, scissors. In other cases it lies beyond the forces, e.g. sugar-tongs, nut-cracker, claw-ham- mer, a wheelbarrow. See Mectia.mcs. LEVER, Charles .Tames (1806-72). An Irish novelist, born in Dublin, August .31, 1806. He graduated B. A. from Trinity College, Dublin, in 1827, and then studied medicine at Oiittingen, Germany. A visit to Canada in 1820 he subse- quently turned to good use in Arthur O'Lean/ (1S44) and Con Oregon (1840). Returning to Dublin, he took his medical degree at Trinity (1831), and received several appointments from the Board of Health. In the Dublin I'nirersitti Magazine for February, 1837, appeared the first installment of Barrii Lorrequer. This was fol- lowed by Charles O'ilalley, Jack Hinton. the Guardsman, Tom Burke of Ours. The Martins of Cro' Martin, and Roland Cashel. These novels, pervaded with a spirit of farcical humor, were innnensely popular. By 1850 the vein had, how- ever, been a little too well worked. Lever dis- ])layed a quieter humor in The Oodd Family Abroad (1853-54), depicting English life on the Continent. His later work is less interesting. Ijcver lived much on the Continent and there gathered material for his novels. In 1840 he was physician to the British Legation at Brussels. In 1857 he was appointed Consul at Spezia and ten years later at Trieste, where he died .lune 1, 1872. His ^'orks were published by Koutlcdge (33 vols., London, 1876-78; since reprinted), ajid in the Barrington Edition (32 vols., Boston, 1002). Consult his Life, by Fitzpatrick (London, 1870). LEVERET (OF. levrri, diminutive of Icvre. Fr. lit'rre. It. Icpre, hare, from Lat. li-pus. hare). The young of the hare during the first year of its age. See Hare. LEV'ERETT, -loiix (1610-79). An American colonial otlicial. He came to Boston with his father in 1033 from Boston Parish, England, but went back to serve in the Parliamentary Army in 1644. He was a captain inider Cromwell, who became his friend. On his return to Boston he was a member of the General Court (1651-52), and was sent to bring Maine under the jurisdic- tion of Massachusetts. He also took part in tlie capture of settlements along the Saint LawreiU'e. In 1606 he went to England to represent the Colony, and remained six years. On his return he was made Speaker of the General Court and major-general of the militia. For six years he w.qs in the Governor's Council, and was then made Deputy Governor. When Bcllingham died in 1672 he filled out his term. He was regularly elected Governor in 1673, and died in office. Con- sult the Report of the New England Genealogical Society for 1881. LEVERRIER, Ic-var'yu', I^rbaix .Jean .Jo- seph (1811-77). A French astronomer, born at Saint-Lo. He was admitted to the Ecole Polytech- nique in 1831, and was subsequently employe<l for some time as an engineer in connection with the Government tobacco monopoly. His Tables de Mercure and several memoirs on 'the secular inequalities' opened to him the door of the Academy in 1846. At the instance of Arago he applied himself to the examination of the disturbances in the motions of the planets, from which the existence of an undiscovered planet could be inferred; and, as the result of his laborious calculations, directed the attention of astronomers to the point in the heavens where, a few days afterwards, the planet Neptune was actually discovered. The elements of the orbit of the planet had also been calculated by the English astronomer Adams in 1845, but no search was made for the planet. For this Leverrier was rewarded with the grand cross of the Legion of Honor, a professorship of astronomy in the Faculty of Sciences at Paris, and various minor honors. In 1854 Leverrier was appointed to the directorship of the Observatory of Paris, an office which, .save during an interval of three years (1870-73), he held till his death. See Adams, .John CotTrii ; Xeptune. LEVERWOOD. A synonym for ironwood. See Hornbeam.