Sibe'ria (Sibir) was originally heard of as a Tartar stronghold on the Irtish, captured by the Russians in 1580; and gradually widening in scope, the name is now applied to the vast territory belonging to Russia in northern Asia, lying between the Arctic Ocean and the Chinese empire, and extending from the Urals to the Sea of Japan. It covers an area of 4,833,500 sq. m. - nearly forty times as great as that of the United Kingdom - and has a population of 5,727,000. Its natural divisions, broadly corresponding to the administrative ones, are: West Siberia, including the governments of Tobolsk and Tomsk, as also parts of Perm; East Siberia (Yeniseisk, Irkutsk, Yakutsk, and Transbaikalia); Kamchatka; and the Amur region, which includes the governments of Amur, Usuri, the maritime province, and part of the island of Saghalien. The great plateau of eastern Asia enters Siberia to the east of Lake Baikal, where it is 3000-4000 feet high and 1300 miles wide, and stretches thence with a gradually decreasing height and width towards Behring Strait. It is fringed on the W. by the Altai (q.v.) and Sayan mountains, and on the E. by the Stanovoi Mountains. The border-ridges of the plateau attain heights of from 7000 to nearly 11,000 feet, but very few of them penetrate into the region of perpetual snow. A broad alpine belt fringes the plateau to the NW., thickly clothed with forests, and containing several auriferous districts. Another belt of high plains (1700-2500 feet high) spreads all along the base of the alpine belt. The whole of West Siberia, between these high plains and the shores of the Arctic Ocean, is an immense lowland, whose southern part - the prairies of Ishim, Upper Tobol, and Baraba - is extremely fertile, and covered with a luxurious grass-vegetation, with masses of deciduous forest. This is even now the granary of Siberia, and exports grain to the mines of the Urals. Nearly one-third of the population of Siberia is gathered on those prairies, and is more thoroughly Russian than in many parts of European Russia. Farther north, especially between the Obi and the Irtish, begin the urmans, or immense marshes, which cover nearly 100,000 sq. m., clothed with thickets and meagre forests, in which some 30,000 Ostiaks, Voguls, and Samo-yedes find scanty means of existence in hunting and fishing. Farther north still begin the tundras, which extend along the Arctic seaboard as far as Kamchatka, and cover an aggregate area of some 450,000 sq. m., with a really terrible climate. Nevertheless some 50,000 human beings wander over these inhospitable tracts with reindeer and dogs. Of the plateau which fills vast tracts in East Siberia, the upper terrace, 3000 to 4000 feet high, is quite unsuitable for agriculture, but its lower terrace (2500 to 3000 feet), especially in Transbaikalia, is good for tillage and cattle-breeding, and is peopled by both Buriats and Russians; the smaller chains of mountains are rich in gold, copper, iron, and silver. The high plains (1500 to 2000 feet), watered by the Zeyaand its tributaries, and covered with a very fertile soil and excellent oak forests, are the richest part of the Amur territory, and are being rapidly occupied by immigrants, chiefly sectaries, from Russia, who already number about 60,000. Khabarovka, at the junction of the Usuri with the Amur, is the capital of the territory; the excellent harbour of Vladivostok is the terminus (since the loss of Port Arthur in 1905) of the Trans-Siberian railway (over 6500 miles from St Petersburg, and costing over 50 millions sterling). See Amur, Maritime Province, Saghalien, Kamchatka, and New Siberia. The rivers of Siberia are of immense value for navigation. They all rise in the plateau, and each of them receives a tributary only smaller than itself - the Obi, the Irtish; the Yenisei, the Tunguska; and the Lena, the Vitim; whilst the Shilka and Argun unite to form the Amur. Communication in summer by sea has been established between Western Europe and the Obi and Yenisei, on which, as on the Lena, steamers ply, save when they are frozen. On the Amur steamers ply for a distance of 2000 miles. Overland communication is maintained by means of post-stations between all the chief towns - the great highway from Russia to the Pacific passing through Tiumen, Omsk, Tomsk, Krasnoyarsk, Irkutsk, Tchita, Blagoveschensk, and Khabarovka. The chief lake is Baikal (q.v.). Siberia fully deserves its reputation of being the coldest country of the world; but it has a much warmer summer than is generally supposed. In moderate latitudes July has an average temperature of from 61° to 67°, and 69° on the Middle Amur. The hot summer and a cloudless, bright sky favour vegetation, and melons are grown in the open air in the steppes of Minusinsk and Irkutsk. But the summer is short, as a rule, and cold weather sets in very rapidly. Night frosts are usual in September, and in November all rivers are frozen. In November, even in South Siberia, the mercury of the thermometer is occasionally frozen, and in December and January it remains frozen for weeks. In the far north the cold is really terrible; temperatures as low as - 75° and - 85° F. have been measured at Verkhoyansk and Yakutsk. The population of Siberia is very unequally distributed; there are from 20 to 40 inhabitants to the square mile in parts of South Tomsk and Tobolsk, while the deserts of the far north are almost uninhabited. The total population, which was less than 1,000,000 in 1800, has now attained over 5,720,000, and it is yearly increased by some 50,000 Russian immigrants. The Russians in Siberia proper number over 3,800,000. They occupy the best parts of the territory in the south, as well as the valleys of the chief rivers. The indigenous population hardly numbers now 700,000; the Ugrian stock is represented by the Voguls, the Ostiaks, and the Samoyedes on the slopes of the Urals. Various Turkish tribes inhabit the slopes of the Altai and Sayan mountains; the Yakuts number 200,000. The Mongolian race is represented by the Kalmucks (about 20,000 in the Altai), the Buriats (250,000) around Lake Baikal, and the nomadic Tunguses (about 50,000) in the mountains of East Siberia and the Amur region. Nearly 15,000 Manchurians and Chinese stay on Russian territory of the Amur and Usuri; and 3000 Coreans are settled around the Gulf of Peter the Great. Finally, in the north-east there are tribes akin to the Eskimos, including the Tchuktchis, the Koryaks, and the Kamchadales. On the Lower Amur we find the Gilyaks, and in the island of Saghalien the Ainos. The Russians belong to the Greek Orthodox faith, or to some of its nonconformist sects. Most Turkish tribes are Mohammedans. The Buriats profess Bud-dhism; and most of the Ugrian and Finnish peoples are Shamanists. The rapid increase of population which has taken place since 1875 is chiefly due to free immigration. The exiles transported to Siberia have contributed but little to the settled population. The facilities afforded by the Siberian railway have given an extraordinary impetus to dairy-farming in Siberia. From 1898 to 1904 the dairies increased from 140 to 2630 (250 of them co-operative), and the produce from 48,360 cwt. to 681,857 cwt. It is estimated that there are 25 million cows, giving milk rich in butter, of which about 80 million lb. are exported annually, two special lines of steamers from Reval and Riga carrying it in refrigerators to London. Agriculture and cattle-breeding are extending; several large districts now produce more corn than is wanted for the population, and export some. Hunting continues to be profitable in some parts. Sables, Arctic foxes, and gray foxes have become rare; squirrels, common foxes, bears, deer, antelopes, some ermines and a few beavers in the north-east, are still obtained. Fishing is extensively carried on in lakes and rivers. Tiumen builds steamers. In 1860-1900 from 400 to 600 cwt. of gold was annually obtained in East Siberia, and 50 cwt. in West Siberia, exclusive of Perm. Silver is extracted in the Altai; lead in the Altai, and in Nertchinsk; copper in Altai; and much iron. A university has been opened at Tomsk (1888). The Russians began the conquest of the territory in 1580, when a band of Cossack robbers under Yermak subdued the Tartars on the Tobol River. New bands of Cossacks, traders, and hunters supported by the Moscow government, and followed by dissenters flying from religious persecution and peasants escaping from serfdom, poured into Siberia during the next two centuries. The estuary of the Amur was discovered in 1849, and a military post established at the mouth of the river in 1851. The left bank of the Amur and the right bank of the Usuri were annexed in 1853-57. Nordenskiold first circumnavigated Asia in 1878-79. See the relevant parts of Reclus, Geographie Universelle (trans. by Keane), and of Picturesque Russia; Seebohm, Siberia in Asia (1882); Lans-dell, Through Siberia (1882); and books by Ken-nan (1891), Wright (1903), and De Windt (1904).