YENISEI (from a Tungus word meaning Great River), a river of Asiatic Russia, rising in Mongolia and flowing into the Arctic Ocean, having a total length of 2,700 m. and a basin ex tending over a million square miles. It marks a structural bound ary of great antiquity in the history of the continent. The western plain, extending from the Urals and covered by quaternary allu vial deposits, with a few isolated remnants of friable Tertiary sandstones, forms, apart from the smaller rivers of the Arctic tundra, a catchment area for the Ob. Near the left bank of the Yenisei there is a slight rise in the plain which deflects a few short tributaries to the Yenisei, but most of its drainage area lies to the right, on the ancient plateau remnant of Angara land, the middle of which forms a watershed, with drainage either to the Arctic, or to the east and west. Thus the Yenisei and the Lena are marginal rivers of an ancient block. Contrasts between the land to the west and that to the east of the Yenisei, north of Krasnoyarsk, are sharp, orographically, geologically, in soil formation and in climate, the winter isotherms curving southward on the higher land. The effects are that the plateau population is scanty, and that the limit of possible cultivation, which from the Urals to long.
50° E. remains considerably north of lat. 6o° N., on the plateau lies considerably farther south. North of the Arctic circle, the difference disappears, the whole region being tundra.
Towards the south the plain forms an amphitheatre west of Lake Baikal; within it lie the courses of the Angara, the Stony or Middle Tunguska, the upper courses of the Lower Tunguska and of the Lena. It is bounded by the Archaean masses on the Middle Yenisei, cut off by a fracture along the river between the confluences of the Angara and the Stony Tunguska, and by the pre-Cambrian fold mountains to the south. Bogdanovich supposes that a great inland lake existed in the amphitheatre during the Angara epoch of the Mesozoic. The Yenisei is thus a mountain river of composite character. In Chinese Mongolia it flows through a longitudinal valley at the northern foot of the Tannu-ola; it then cuts through the western Sayan mountains and passes through portions of successive transverse valleys to Krasnoyarsk and its confluence with the Angara. It then flows along the western
base of the Archaean range and finally enters the most north westerly part of the Palaeozoic plateau. The Yenisei is formed by the junction of the Bei-kem and Chua-Kem streams in the Uryan khansk district of Chinese Mongolia, and is known as the Ulu kern or Upper Yenisei. It receives the Kemchik river on the left and the town of Kemchik at the junction is much visited by Rus sian traders, who also have quarters in Krasniy at the junction of the Bei-kem and Chua-kem (or Little Yenisei).
After crossing the frontier it receives the Us on the right bank and there is a Russian settlement at Usinskoe. Eighty-two miles north of the frontier are formidable rapids, the limit of raft navi gation. This part of its course is through coniferous mountain forest, with some meadow land along the banks. Gold, asbestos, salt, coal, magnesia and iron occur in the mountains, but are little worked; the inhabitants are mainly nomad Finno-Tatar hunters, though Russian colonization is slowly spreading. The river now enters a prairie region, with the Abakan draining it on the left and the Tuba on the right. Minusinsk (q.v.) lies 8 m. from the confluence of the Abakan and Yenisei; and the Minusinsk black earth region, sheltered by the West Sayan mountains, the Siberian Urals and the Abakan range, is noted for its fertility and its mild climate and has been settled from prehistoric times. Gold and coal are found. Iron is found on the Irba, a tributary of the Tuba. At Novo-Selovsk 55° 5' N., 91° 16' E., the Chulim, a tributary of the Ob is only 6 m. distant, but canalization is im practicable owing to difference of level. At Krasnoyarsk (q.v.) the railway crosses the river, which here flows through a plain with mountains to the south and west, whose red sandstone and marl have given Krasnoyarsk its name.