TANEY. 21 in the noted case of Ex-parte Merryman in an- swer to an application for a writ of habeas corpus in behalf of a citizen of Jialtiniore who had been arrested by a United States ollicor on a charge of treason, denying in strong and vigor- ous language the right of the President to sus- pend the writ of habeas corpus and affirming that that power was vested in Congress alone. A memoir of Taney's life, in part an autobiog- raphy, was published in 1872 bj' Samuel Tj-ler. T'ANG, tiing. One of the seven most cele- brated dynasties of China. It lasted from 618 to 907 and was founded by Li Yuan, a soldier and a descendant of one of the princely houses, who, after a reign of eight years, during which man}- reforms were introduced, abdicated in fa- vor of his second son, Li Shih-min, the real uni- fier of the Empire and the most illustrious of the T'ang rulers (627-649). With the twelfth Emperor decay began to set in and in 907 the line came to an end. In 923 a descendant of one of the T'ang emperors established the Posterior T'ang, which came to an end in 936 under its fourth Emperor. The T'ang is undoubtedly one of the most bril- liant periods of Chinese history. The Empire was extended to the Caspian Sea and China itself was divided into fifteen provinces. In 628 a maternal uncle of Mohammed visited China and built the mosque at Canton, and a century and a half later 4000 Mohammedan soldiers, whose descendants now form an iniix>rtant ele- ment of the population, settled in the country. Learning and literature were fostered, the Han- lin Yuan (q.v. ) had its beginning, and Budd- hism, Taoism, and even Nestorian Christianity flourished under Imperial patronage. Paper money was then first used and the Peking Gazette was founded. TANGANYIKA, tiin'gan-ye'ka. A large lake in Central Africa, extending from latitude 3° 16' to 8° 48' S., and from longitude 29° 20' to 31° 20' E. (Map: Africa, H 5) . Its northern end is 175 miles southwest of the Victoria Nyanza, and its southern end 190 miles northwest of Lake Nyassa. It lies in the western branch of the Great Rift Valley (q.v.), which is interrupted at the south end of the lake by a plateau, but continued farther to the southeast as the basin of Lake Nyassa. Tanganyika extends in a north and south direction, with a length of 400 miles and a breadth of 20 to 40 miles. Its area is estimated at over 12.000 square miles. Its basin, which includes a nari-ow strip of fertile lowland along either shore, is bounded by the high and steep sides of the Rift Valley, which in some places form precipitous rocky cliffs, and reach a height of 4200 feet above the level of the lake, which is 2700 feet above the sea. The depth is very great, ranging in the greater portion from ,500 to over 2000 feet, and the lake is remarkably free from shoals, reefs, or islands. There are, however, floating islands of vegetation, the shores being often very densely forested with palms. Navigation is also rendered dangerous by severe hurricanes and tornadoes to which the basin is subject. The lake is fed by numerous small streams from the .surrounding plateau, and dis- charges into the Conso through the Lukiiga, which leaves it near the middle of the western shore. This discharge, however, is intermittent, and the level of the lake is subject to periodic TANGERMANN. flueturitions, each of which may range over a scries of years. The fall of the lake level in re- cent times has amounted to two feet annually. Though the water is, as a wdiole, fresh, it has in some portions a tendency to become brackish. The fauna of the lake is very ricli and peculiarly interesting. IJesides the usual fresh-water lish, crocodiles, and hippopotamuses, all of which are abundant, there are a number of peculiar iso- lated groups of deep-water niollusks and crabs wdiich are asserted to be of marine origin. This fact points to the theory that in Jurassic or Cretaceous times the lake was an arm of the sea which became isolated by subsequent up- heavals. Politically the west shore belongs to the Congo Free State, the east shore to German East Afri- ca, and the south shore to the British colony of Rhodesia. All three powers have trading and mission stations on the shores, and several steamers have been launched on the lake. Of the ninnerous native towns the largest is Ujiji, on the east shore. Lake Tanganyika was discovered in 1858 by Burton and Speke. and later explored b.v Livingstone, Cameron, Stanley, and others. Consult Peters, Das deutsch-ostrafrikanische Schutzgebiet (Munich, 1895). TANGENT (Lat. tangcns, pres, part, of tangcre, to touch; connected with Goth, trkan, leel. taka, AS. tacan, Eng. take). An unlimited straight line which meets a curve in but one point, without cutting it. The point is called the point of contact or point of tangency. A tangent may be thought of as the limiting posi- tion of a secant, the point of tangency being the point in which the points of intersection of the secant with the curve coincide. In the circle there is but one distinct tangent at any point in the circumference, and this is perpendicular to the radius at that point. The segments of two tangents to a circle from an external point, lim- ited by the point and the points of contact, are equal. If the point moves up to the circumfer- ence, the segments become zero and the tangents coincide; if the point moves inside the circum- ference, the tangents become imaginary. (See Continuity.) All conic sections being of the second class (see CuBVE) admit of but two tan- gents from any point. Curves belonging to high- er classes admit of a greater number, depending upon the class. Tangents are of different orders of contact (see CoNT.iCT) according to the num- ber of coincident points at the point of tangency, and thus serve to distinguish various singulari- ties of curves. (See Cukve.) In coordinate geometry the projection, upon the X-axis, of the segment of the tangent between the point of contact and the X-axis is called the subtangent. An important class of tangents are known as asymptotes (q.v.). In the geometry of surfaces the tangent plane corresponds to the tangent line of curves. The extensive list of properties involving tangents is best obtained from works on analytic geometry, TANGERMANN, tiing'er-man. Wiuiei.m (1815—), A German Old-Catholic theologi.an, known as an author by the pseudonym Victor Granella, He was born at Essen-on-the-Ridir and studied theology at Miinster and Munich. In 1840 he became priest at Neuss and afterwards held several prominent positions in his Church. In 1870 he was deprived of his offices because of
