Mr. Bryce points out that the physical features of a people are determined chiefly by their environment. These illustrations show (at top) a typical English settler in the old Colonial days of America, a native Red Indian (left) and a typical American of to-day (right). Without any intermingling of red men and white, the modern American, thanks to climatic conditions, resembles the Red Indian far more closely than he does his own ancestors of the Colonial days. ] As Nature must have been the main agent in the formation of the various races of mankind from a common stock, so also Nature has been the chief cause of their movements from one part of the earth to another, these movements having been in their turn a potent influence in the admixture of the races. Some geographers have alleged climate--that is to say, the desire of those who inhabit an inclement region to enjoy a softer and warmer air--as a principal motive which has induced tribes of nations to transfer themselves from one region to another. It is no doubt true that the direction of migrations has almost always been either from the north towards the south, or else along parallels of latitude, men rarely seeking for themselves conditions more severe than those under which they were born. But it is usually not so much the wish to escape cold that has been an effective motive as the wish to find more and better food, since this means an altogether easier life. Scarcity of the means of subsistence, which is, of course, most felt when population is increasing, has operated more frequently and powerfully than any other cause in bringing on displacements of the races of man over the globe. The movement of the primitive Aryans into India from the plateaux of West Central Asia, probably also the movement of the races which speak Dravidian languages from South Central Asia into Southern India, and probably also the mighty descent, in the fourth and fifth centuries A.D., of the Teutonic races from the lands between the Baltic and the Alps into the Roman Empire, had this origin. [Sidenote: The Colonising Impulse]