opulated as many temperate countries.[1416] [See
maps pages 8, 9, and 612.] The fact that they are for the most part
dependencies or former colonial possessions of European powers indicates
their retarded economic and political development. The contrast between
the Mongol Tunguse, who lead the life of hunters and herders in Arctic
Siberia, and the related Manchus, who conquered and rule the temperate
lands of China, shows how climates help differentiate various branches
of the same ethnic stock; and this contrast only parallels that between
the Eskimo and Aztec offshoots of the American Indians, the Norwegian
and Italian divisions of the white race.

[Illustration: MEAN ANNUAL ISOTHERMS AND HEAT BELTS [_Centigrade_]
0 deg.C = 32 deg.F. 20 deg.C = 68 deg.F. 30 deg.C = 86 deg.F.]

[Sidenote: Temperature as modified by oceans and winds.]

The zonal location of a country indicates roughly the degree of heat
which it receives from the sun. It would do this accurately if
variations of relief, prevailing winds and proximity of the oceans did
not enter as disturbing factors. Since water heats and cools more slowly
than the land, the ocean is a great reservoir of warmth in winter and of
cold in summer, and exercises therefore an equalizing effect upon the
temperature of the adjacent continents, far as these effects can be
carried by the wind. The ocean is also the great source of moisture, and
this, too, it distributes over the land through the agency of the wind.
Where warm ocean currents, like the Gulf Stream and Kuro Siwa, penetrate
into temperate or sub-polar latitudes, or where cool ones, like the
Peruvian and Benguela Currents wash the coasts of tropical regions, they
enhance the power of the ocean and wind to mitigate the extremes of
temperature on land. The warm currents, moreover, loading the air above
them with vapor, provide a store of rain to the nearest wind-swept
land. Hence both the rainfall and temperature of a given country depend
largely upon its neighboring water and air currents, and its
accessibility to the rain-bearing winds. If it occupies a marked
central position in temperate latitudes, like eastern Russia or the
Great Plains of our semi-arid West, it receives limited moisture and
suffers the extreme temperatures of a typical continental climate. The
same result follows if it holds a distinctly peripheral location, and
yet lies in the rain-shadow of a mountain barrier, like western Peru,
Patagonia and