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

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

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

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

Although farming of any sort was almost as impossible in the plains as in the dry regions of winter rains farther west, the abundance of buffaloes made life much easier in many respects.

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.

We are learning, too, that the love of beauty is one of Nature's greatest healers.