70 : PHYSICAL GEOGRAPHY.

 

 

lake-regions of the world are almost entirely
confined to the northern continents.
191. Oceanic Drainage Systems.—North Amer-

ica contains the most extensive lake-system in the.

world. The lake-region surrounds Hudson Bay,
and drains into the Arctic through the Mac-
kenzie; into Hudson Bay through the Sas-
katchewan; or into the Atlantic through the
St. Lawrence. To it belong the Great Lakes—
Superior, Michigan, Huron, Erie, and Ontario—

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

embracing a combined area of nearly 100,000
square miles—and the numerous lakes of Brit-
ish America. —

Athabasca, Great Slave, and Great Bear Lakes drain
into the Arctic through the Mackenzie; Lake Winnepeg,
into Hudson Bay through the Nelson; and the Great
Lakes, into the Atlantic through the St. Lawrence.

Europe contains two extensive systems of fresh-
water lakes. The larger region is in Low Europe,
and surrounds the Baltic Sea and its branches;
to it belong Lakes Ladoga and Onega in Russia,
Wener and Wetter in Sweden, with numerous
smaller lakes. The smaller region is found in
the Alps in High Europe.

Africa contains an extensive system of lakes
west of the predominant system. Victoria ‘and
Albert Nyanzas, which drain into the Nile, Lake
Tanganyika, which drains into the Livingstone

 

 

 

or the Congo, and Lake Nyassa, which drains
into the Zambezi, are the principal lakes.

The remaining continents contain but few large
fresh-water lakes. In South America we find Lake
Maracaybo, with brackish water from its vicinity
to the sea; and in Asia, Lake Baikal.

192. The Inland Drainage Systems are inti-

mately connected with that of inland rivers. The
term Steppe Lakes and Rivers is generally applied .
to those which have no outlet to the ocean.

Cause of the Saltness of Inland Waters.—All river-
water contains a small quantity of common salt and other
saline substances. Since lakes which have no outlet, or,
as they are generally called, inland lakes, lose their waters
by evaporation only, the saline ingredients must be con-
tinually increasing in quantity; the water of such lakes
is therefore generally salt.

The Dead Sea in Syria is remarkable for the quantity
of its saline ingredients. In every one hundred pounds
of its waters there are over twenty-six pounds, or more
than one-fourth, of various saline ingredients.

North America.—The largest inland drainage-
system is in the Great Basin, containing Great
Salt, Walker, Pyramid, and Owen Lakes.

South America.—The largest.region of inland
drainage includes the plateau of Bolivia, contain-
ing Lake Titicaca. The waters of this lake are .
fresh, but have no outlet to the sea, the river form-
ing the outlet being lost in a salty, sandy plain.

Europe and Asia contain a vast region of in-
land drainage extending from the Valdai Hills
eastward to the Great Kinghan Mountains, em-
bracing most of the Asiatic plateaus.

The region contains Lake Elton in Russia, and the Cas-
pian and Aral Seas. The combined area of the last two
is 175,000 square miles. They receive the waters of the
Volga, the Ural, the Sir, and the Amoo, all large streams.
Numerous Jakes occur on the plateaus. Lake Lop, in the

depression north of Thibet, receives the Tarim, and Lake
Hamoon, on the Iranian plateau, the Helmund River.

Africa contains Lake Tchad in the Soudan, re-
ceiving the Komadagu and the Shirwa, and Lake
Ngami in Southern Africa. —

Australia contains Lakes Eyre, Torrens, Gaird-
ner, and Amadeo near the southern coast.

193. Utility of Lakes.—By offering extended basins
into which the rivers, when swollen, can disgorge them-—
selves, lakes greatly diminish the destructive effects of
jnundations, often checking them entirely. They afford
extended surfaces for evaporation, and, collecting the finer
sediment of the rivers when deserted by their waters,
form fertile plains.

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