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.

America forms the longest and straightest bone in the earth's skeleton.

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.

A journey of four hundred and thirty miles can be made in any part of the United States, but in Turkey it takes as many days.

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.

Man could not stay there forever. He was bound to spread to new regions, partly because of his innate migratory tendency and partly because of Nature's stern urgency.