cess of evaporation we are describing takes place in the case of
all lakes, though only here and there is the air so dry that the
evaporation prevents the basin from overflowing at the lowest point on
its rim, forming a river which goes thence to the sea. Even in the
case of the Great Lakes of North America a considerable part of the
water which flows into them does not go to the St. Lawrence and thence
to the sea. As long as the lake finds an outlet to the sea its waters
contain but little more dissolved mineral matter than that we find in
the rivers. But because all water which has been in contact with the
earth has some dissolved mineral substances, while that which goes
away by evaporation is pure water, a lake without an outlet gradually
becomes so charged with these materials that it can hold no more in
solution, but proceeds to lay them down in deposits of that compound
substance which from its principal ingredient we name salt. The water
of dead seas, because of the additional weight of the substances which
it holds, is extraordinarily buoyant. The swimmer notes a difference
in this regard in the waters of rivers and fresh-water lakes and those
of the sea, due to this same cause. But in those of dead seas,
saturated with saline materials, the human body can not sink as it
does in the ordinary conditions of immersion. It is easy to understand
how the salt deposits which are mined in many parts of the world have
generally, if not in all cases, been formed in such dead seas.[5]

[Footnote 5: In some relatively rare cases salt deposits are formed in
lagoons along the shores of arid lands, where the sea occasionally
breaks over the beach into the basin, affording waters which are
evaporated, leaving their salt behind them.]

It is an interesting fact that almost all the known dead seas have in
recent geological times been living lakes--that is, they poured over
their brims. In the Cordilleras from the line between Canada and the
United States to central Mexico there are several of these basins. All
of those which have been studied show by their old shore lines that
they were once brimful, and have only shrunk away in modern times.
These conditions point to the conclusion that the rainfall in
different regions varies greatly in the course of the geologic ages.
Further confirmation of this is found in the fact that very great salt
deposits exist on the coast of Louisiana and in northern
Europe--regions in which the ra