No part of the world can be truly understood without a knowledge of its garment of vegetation, for this determines not only the nature of the animal inhabitants but also the occupations of the majority of human beings.

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.

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.

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.

In America the most widespread type of forest is the evergreen coniferous woodland of the north.

With every throb of the climatic pulse which we have felt in Central Asia,, the centre of civilisation has moved this way and that. Each throb has sent pain and decay to the lands whose day was done, life and vigour to those whose day was yet to be.

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.