tic latitudes and high altitudes by drawing the dead-line to all
organic life. It dominates life in steppes and torrid deserts as in
sub-polar wastes. It encourages intimacy with the sea in tropical Malays
and Polynesians, and like a slave-driver, scourges on the fur-clad
Eskimo to reap the harvest of the deep. It is always present in that
intricate balance of geographic factors which produces a given
historical result, throwing its weight now into one side of the scales,
now into the other. It underlies the production, distribution and
exchange of commodities derived from the vegetable and animal kingdoms,
influences methods of agriculture, and the efficiency of human labor in
various industries.[1409] Hence it is a potent factor in the beginning and
in the evolution of civilization, so far as this goes hand in hand with
economic development.

[Sidenote: Climate in the interplay of geographic factors.]

The foregoing chapters have therefore been indirectly concerned with
climate to no small degree, but they have endeavored to treat the
subject analytically, showing climate as working with or against or in
some combination with other geographic factors. This course was
necessary, because climatic influences are so conspicuous and so
important that by the older geographers like Montesquieu[1410] and others,
they have been erected into a blanket theory, and made to explain a wide
range of social and historical phenomena which were properly the effect
of other geographic factors.

[Sidenote: Direct and indirect effects of climate.]

For a clear understanding of climatic influences, it is necessary to
adhere to the chief characteristics of the atmosphere, such as heat and
cold, moisture and aridity, and to consider the effect of zonal
location, winds and relief in the production and distribution of these;
also to distinguish between direct and indirect results of climate,
temporary and permanent, physiological and psychological ones, because
the confusion of these various effects breeds far-fetched conclusions.
The direct modification of man by climate is partly an _a priori_
assumption, because the incontestable evidences of such modification
are not very numerous, however strong the probability may be. The
effect of climate upon plant and animal life is obvious, and immediately
raises the assumption that man has been similarly influenced. But there
is this difference: in contrast to the helpless dependence upon
enviro