HYDROGRAPII Y. The Arctic rivers flowing through the Siberian low lands and the Amur of the Pacific have great length and very extensive basins. The four great rivers, the Ob, Yenisei, Lena, and Amur (qq.v.), with their numerous tributaries, afford about 30,000 miles of interior navigation. The Ob and its tributary the Irtysh are the most important rivers of Siberia, flowing as they do through the most fertile and populous di,stricts in the southwest of the country. The Oh with its affluents supplies more than 9000 miles of navigation. Its estuary ou the Kara Sea is very large, but vessels drawing more than 12 feet cannot enter it. Its long tributary, the Irtysh, is also navigable. The Yenisei is navi gable for 1850 miles and ocean steamers might as cend it for 1000 miles. The ice-choked northern sea, however, makes the Yenisei as well as the Ob unimportant in sea trade. Local trade and steam navigation are developing along the river, but its chief importance is as a link in the line of water communication between Lake Bai kal in Eastern Siberia and Tiumen, near the west ern boundary, a very important route more than half way ac•o.ss Siberia. This route is by way of the Angara tributary of the Yenisei from Lake Baikal and Irkutsk by steamer 400 miles to Bratski Ostrog, where rapids obstruct steam navi gation, though the improvements required to make steamers available around the worst rapids (11/4 miles) would not he very costly. Thence the
route is nninterrupted to the Yenisei, down that river to the Kass, whose source lies near that of the let tributary of the Ob. These rivers were canalized and connected by a canal, so that boats pass between the Yenisei and the Ob (586 miles). The route continues on the Irtysh and its Tobol tributary to 'Mullen, over 3000 miles by water from Irkutsk. At that point freight is trans ferred between boat and railroad.
The Lena is navigable by river steamers for 1750 miles from its mouth, and serves consider able local traffic. The Yana and Kolima, other large Arctic rivers, are still little known. The Anon• basin supplies 8940 miles of navigation in cluding the Amur, the Shilka and Ingoda, the Seya and its tributaries, the Sungari and its tributaries, and the Ussuri. The great commercial disadvantage of the Siberian rivers is that they are open to navigation only from three to five months in the year. Lake Baikal, the largest fresh-water lake in Asia, is in Eastern Siberia. Considerable agriculture is developing around its shores and the Government has constructed a number of ports to facilitate the lake trade.