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

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

Year by year we are learning that in this restless, strenuous American life of ours vacations are essential.

The human organism inherits so delicate an adjustment to climate that, in spite of man's boasted ability to live anywhere, the strain of the frozen North eliminates the more nervous and active types of mind.

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

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.

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.