Thus the races, though alike in their physical response to climate, may possibly be different in their mental response because they have approached America by different paths.

No part of the world can be truly understood without a knowledge of its garment of vegetation, for this determines not only the nature of the animal inhabitants but also the occupations of the majority of human beings.

In fact, the history of North America has been perhaps more profoundly influenced by man's inheritance from his past homes than by the physical features of his present home.

History in its broadest aspect is a record of man's migrations from one environment to another.

Curiously enough man's body and his mind appear to differ in their climatic adaptations.

Except on their southern borders the great northern forests are not good as a permanent home for man.

Although mountains may guide migrations, the plains are the regions where people dwell in greatest numbers.