BAIKAL (known to the

See also:

• MONGOLS

Mongols as Dalai-nor, and to the

See also:

• TURKISH

Turkish tribes as Bai-kul)  , a lake of East Siberia, the sixth in size of all the lakes of the world and the largest fresh-water basin of Eurasia . It stretches from S.W. to N.E . (51° 29' to 550 50' N. lat. and 103° 40' to 11o° E. long.), separating the government of Irkutsk from that of Transbaikalia, and has a length of 386 m. and a width of from 20 M. to 50 M . Its southern extremity penetrates into the high plateau of Asia, and the lake lies entirely in the Alpine zone which fringes that plateau on the north-west . Its area is 13,200 sq . M., i.e. nearly as great as Switzerland . The length of its coast-line is 525 M. along the western, and 64o m. along the eastern shore . Its altitude has been estimated at 1587 ft . (Chersky) and at 1679 ft . (Suess)—118 ft. above the level of the Angara at Irkutsk (Zapiski Russ . Geog . Soc. xv., 1885); but 1500 ft. would seem to be a more correct altitude (Izvestia East Sib .

Branch, xxviii . 1, 1897), Its level is subject to slight oscillations, and after a heavy five weeks' rain in 1869 it rose 7 ft., an immense territory at the mouth of the Selenga being submerged . A hydrographic survey of this lake was made by Drizhenko in 1897–1902 . The elongated hilly island of Olkhon, and the peninsula of Svyatoi Nos, which forms its continuation on the opposite eastern shore, divide the lake into two basins . The deepest part is in the south-east, at the foot of the Khamardaban border-ridge of the high plateau . An elongated trough, 66 m. long, reaches there a depth of over 600 fathoms, with a maximum depth of 88o fathoms, i.e. about 5280 ft. below the level of the ocean . As a rule the bottom of the lake has very steep slopes : the Too-fathom and even the 250-fathom lines run close to the shores, that is to say, the steepness of the surrounding mountains (4600 to 6000 ft.) continues beneath the surface . At the mouth of the Selenga, however, which enters from the south-east, pouring into it the waters and the alluvial deposits from a drainage area of 173,500 sq . M., a wide delta is thrust out into the lake, reducing its width to 20 M. and spreading under its waters, so as to leave only a narrow channel, 230 to 247 fathoms deep, along the opposite coast . The depth of the middle portion of the lake has not yet been measured, but must exceed 500 fathoms . It was expected that an under-ground ridge would be found connecting Olkhon with Svyatoi Nos; but depths exceeding 622 fathoms have been sounded even along that line . As to the northern basin, the configuration of its bottom is in accordance with the high mountains which ' See L .

Pinvert, Lazare de Baif, 1496 ?–1547 (1900) . 215 surround it, and most of its area has a depth exceeding 400 fathoms, the maximum depths along three lines of soundings taken across it being 491, 485, and 476 fathoms respectively . The water is beautifully clear . Temperature.—The surface-layers of this immense basin are heated in the summer up to temperatures of 551° to 570 F., both close to the shores and at some distance from the mouth of the Selenga ; but these warmer layers are not deep, and a

uniform temperature of nearly 39° F. is generally found at a depth of 20 fathoms, as also on the surface in the middle of the lake . At a depth of 500 fathoms there is a nearly uniform temperature of 38° . At various places round the shores, e.g. the mouth of the Barguzin, hot springs exist . The lake freezes usually at the end of December, or in the beginning of January, so solidly that a temporary post-horse station is erected on the ice in the middle of the lake, and it remains frozen till the second half of May . The evaporation from this large basin exercises a certain influence on the climate of the surrounding country, while the absorption of heat for the thawing of the ice has a notable cooling effect in early summer . Rivers.—Lake Baikal receives over 300 streams, mostly short mountain torrents, besides the Upper Angara, which enters its north-east extremity, the Barguzin, on the east, and the Selenga on the south-east . Its only outflow is the lower Angara, which issues through a rocky cleft on the west shore . The Irkut no longer reaches the Baikal, though it once did so . After approaching its south-west extremity it abandons the broad valley which leads to the lake, and makes its way northwards through a narrow gap in the mountains and joins the Angara at Irkutsk .

Mountains.—With the exception of the delta of the Selenga, Lake Baikal is surrounded by lofty mountains . The Khamardaban border-ridge (the

summit of a mountain of the same name is 5300 ft. above the lake), falling with steep cliffs towards the lake, fringes it on the south; a massive, deeply-ravined highland occupies the space between the Irkut and the Angara; the Onot and Baikal ridges (also Primorskiy) run along its north-west shore, striking it diagonally; an Alpine complex of yet unexplored mountains rises on its north-east shore; the Barguzin range impinges upon it obliquely in the east; and the Ulanburgasu mountains intrude into the delta of the Selenga . Geology.—It is certain that in previous geological ages Lake Baikal had a much greater extension . It stretched westwards into the valley of the Irkut, and up the lower valleys of the Upper Angara and the Barguzin . Volcanic activity took place around its shores at the end of the Tertiary or during the Quaternary Age, and great streams of lava cover the Sayan and Khamar-daban mountains, as well as the valley of Irkut . Earth-quakes are still frequent along its shores . Fauna.—The fauna, explored by Dybowski and Godlewski, and in 'goo–2 by Korotnev, is much richer than it was supposed to be, and has quite an original character; but hypotheses as to a direct communication having existed between Lake Baikal and the Arctic Ocean during the Pest-Tertiary or Tertiary ages are not proved . Still, Lake Baikal has a seal (Phoca vitulina, Phoca haikalensis of Dybowski) quite akin to the seals of Spitsbergen, marine sponges, polychaetes, a marine mollusc (ancilodoris), and some marine gammarids . The waters of the lake swarm with fish (sturgeons and salrnonidae), and its herring (Salina omul) is the chief product of the fisheries, though notably fewer have been taken within the last forty or fifty years . Planktonis very abundant . The little Lake Frolikha, situated close to the northern extremity of Lake Baikal and communicating with it by means of a river of the same name, contains a peculiar species of trout, Salmo erythreas, which is not known elsewhere . Generally, while there is a relative poverty of zoological groups, there is a great wealth of species within the group .

Of gammarids, there are as many as 300 species, and those living at great depths (330 to 380 fathoms) tend to assume abyssal characters similar to those displayed by the deep-

sea fauna of the ocean . Navigation.—Navigation of the lake is rendered difficult both by sudden storms and by the absence of good bays and ports . The principal port on the western shore, Listvinichnoe, near the outflow of the Angara, is an open roadstead at the foot of steep mountains . Steamers ply from it weekly to Misovaya (Posolskoe) on the opposite shore, a few times a year to Verkhne-Angarsk, at the northern extremity of the lake, and frequently to the mouth of the Selenga . Steamers ascend this river as far as Bilyutai, near the Mongolian frontier, and bring back tea, imported via Kiakhta, while grain, cedar nuts, salt, soda, wool and timber are shipped on rafts down the Khilok, Chikoi and Uda (tributaries of the Selenga), and manufactured goods are taken up the river for export to China . Attempts are being made to render the Angara navigable below Irkutsk down to the Yenisei . In winter, when the lake is covered with ice 3 ft. to 4 ft. thick, it is crossed on sledges from Listvinichnoe to Misovaya . But a highway, available all the year round, was made in 1863-1864 around its southern shore, partly by blasting the cliffs, and it is now (since 1905) followed by the trans-Siberian railway . Further, a powerful ice-breaker is used to ferry trains across from Listvinichnoe to -Misovaya .