ive 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
Khamar-daban 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
880 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 100-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 underground 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
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 55-1/2deg to 57deg 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 39deg 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 38deg. 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