CHARACTERISTICS AND DISTRIBUTION OF LAKES 601 
island of Olkhon. He also says that the position of the River Selenga, 
which enters the lake at right angles on the eastern shore, and that 
of the river Angara, which leaves Lake Baikal, also at right angles, on 
the western shore, seem to indicate that they have once been parts of 
a single stream which was cut in two by the formation of the lake. 
Chersky ^ reckons 336 tributaries to the lake, the most important 
of which are the Upper Angara, the Selenga (which descends from 
the basin of Lake Kosso-gol), the Barguzin, and others ; the only 
visible outlet is by the Lower Angara, a tributary of the Yenisei. 
The water of the lake is clear and transparent, so that the bottom 
can be seen at a depth of 8 fathoms. The hydrography of Lake 
Baikal was studied by a commission under Drizhenko. Previously 
the lake had been regarded as one approaching very nearly the polar 
type, because observations at deep places were almost lacking. 
According to Vosnessensky,^ director of the meteorological and 
magnetic observatory of Irkutsk, it ought to be relegated to the 
category of lakes of the temperate type. Inverse stratification exists 
only during the cold period of the year (December to June) ; in 
summer (June to December) it is direct. At the beginning of the 
months of December and of June the thermal layers become uniform, 
and the temperature from the surface to the bottom hardly varies, 
remaining very near the temperature of maximum density. All 
these changes occur only in the layer from 0 to 1000 feet ; deeper 
than that the temperature remains constant. In the superficial 
layer from 0 to 50 feet the influence of different factors on the 
vertical distribution of temperature is apparent — depth, nearness to 
the shore and to the mouths of great rivers. In the deeper layer, 
from 50 to about 1000 feet, the temperature is very uniformly 
distributed over all the area of the lake. 
Owing to the sudden changes of wind, to the fogs, and to the 
want of protected bays, navigation on Lake Baikal is difficult. From 
the end of May to the beginning of July a north-east wind with the 
local name of " Barguzin blows on the southern part of the lake, and 
from August there is the " Kultak coming also from the north-east. 
The strongest winds are called " Sorma,'' and blow from the north- 
west, producing short but high waves, which sometimes rise to the 
height of 4 feet. During storms, which occur frequently but are of 
short duration, the waves of the Baikal rise to 6 or 7 feet. In June 
and July the Baikal is almost calm, and during this lull numerous 
aquatic plants float on the surface of the water. The lake begins 
to freeze in November, but it is never frost-bound before the middle 
1 Guide to Great Siberian Raihoay, p. 331. 
2 See Schokalsky and Schraidt, Sur les Explorations scientijiques des Mers et des 
Eaux douces de 1' Empire russe, p. 48, 1907. 
