Fertile soil, level plains, easy passage across the mountains, coal, iron, and other metals imbedded in the rocks, and a stimulating climate, all shower their blessings upon man.

Geologists are rapidly becoming convinced that the mammals spread from their central Asian point of origin largely because of great variations in climate.

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

It will be a vast boon to mankind when we learn to prophesy the precise dates when cycles of various kinds will reach definite stages.

As a matter of fact, an ordinary desert supports a much greater variety of plants than does either a forest or a prairie.

From first to last the civilization of America has been bound up with its physical environment.

For the source of any characteristic so widespread and uniform as this adaptation to environment we must go back to the very beginning of the human race.