of its basin, will in course of time become rich in various kinds
of salt.

No two of the lakes of the Great Basin are alike in the composition
of their waters. This fact may be due to a difference in the rocks
about the lake basin, to the presence of varying mineral springs,
or to the drying up of one or more of the lakes at some time so
that their former salts were buried under sands and clays when
the water again filled the basin.

Great Salt Lake contains little besides common salt. In Mono Lake,
soda and salt are equally important constituents, while Owens Lake
contains an excess of soda. In other basins borax was present in
such quantities that when the waters dried up it formed important
deposits. The value of these deposits is now fully understood, and
many enterprising companies are at work separating and purifying
the borax.

Owens Lake was once fresh, although now it is so strong with soda
that it would destroy the skin if a bather should remain in it very
long. The former outlet of this lake was toward the south, through
a pass separating the Sierra Nevada from the Coso Mountains. For a
distance of thirty miles the old river-bed has been transformed
into a wagon road, and it is interesting to ride all day along the
bed of this dead river, past bold cliffs against which the waters
once surged and foamed. The river emptied far to the south, into a
broad, shallow lake whose former bed is now white with soda and
borax. The old beach lines stand out distinctly upon the slopes of
the enclosing mountains.

The lake bed is now the seat of an important industry--the gathering
of the borax and its refining. There are extensive buildings at
one spot upon its border, and men come and go across the blinding
white surface. A twenty-mule team dragging three huge wagons creeps
slowly along the base of the distant mountains, but all that can
be distinguished is a cloud of dust.

[Illustration: FIG. 45.--FREIGHTING BORAX ACROSS THE DESERT]

The slow crumbling of the rocks, and the setting free of those
constituents which are soluble, the work of the streams in gathering
the rock waste into the lakes, the dry air and the heat of the long
summer days, have all conspired together to give us these valuable
deposits in the dried-up lakes of the Great Basin.

No portion of the earth seems to be without value to man. The great
bodies of water are convenient highways. The rich valleys and timbered
mountains offer useful pro