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.

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

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.

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

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

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.