illes. The sudden southward drop of the 0 deg.C.
annual isothermal line toward the St. Lawrence and the Great Lakes
brought the northwestern fur trade to the back gate of New York, where
it opened on the Mohawk and upper Hudson, and brought prosperity to the
young colony. Even to-day the center of collection for the Canadian fur
fields is Quebec, located at 47 deg. north latitude, while the corresponding
point of concentration in Europe for the furs of Russia and Siberia is
Nizhni-Novgorod, which lies ten degrees farther north.[1426]

[Sidenote: Effect of slight climatic differences.]

This compression of the isotherms emphasizes the differences of national
characters produced in part by dissimilar climatic conditions. Contrasts
in temperament, manner of life, and point of view, like that between the
New Englander and Virginian, Chilean and Bolivian in the Americas,
Breton and Provencal in France, Castilian and Andalusian in Spain,
Gurkha and Bengali in India, seem to bleach out when they are located
far apart, owing to many grades of transition between; but they become
striking, stimulating, productive of important economic and political
results, when close juxtaposition enables them to react sharply one upon
the other. In effecting these nice differentiations of local types,
climate is nearly always one of the factors at work, emphasizing perhaps
an existing ethnic difference. Even the slight variations of
temperature to be found in the same zone or the same climatic region
produce distinct results, especially where they are harnessed, as is
usually the case, with some other geographic condition of relief, area
or soil, pulling in the same direction. Mexico, Peru, Italy,
Switzerland, Greece and Asia Minor, with its high plateau interior and
its contrasted Euxine and Aegean coasts, represent each a complex of
climatic differences, which, reinforced by other geographic factors,
have made in these regions a polychrome picture of national life.

[Sidenote: Effect of climate upon distribution of immigration]

Climatic contrasts aid differentiation also by influencing both natural
and artificial selection in the distribution of peoples. This effect is
conspicuous in the distribution of immigrants in all colonial lands like
Africa, South America and in every part of the United States.[1427] The
warm, moist air of the Gulf and South Atlantic States is attracting back
to the congenial habitat of the "black belt" the negroes