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.

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

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.

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.

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.

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.

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.