Westwards we have the Pacific line of bracing highlands, running down from Mexico as far as Chile, the home of two or more cultures of a rather high order.

Then to the east there is the steaming equatorial forest, first covering a fan of rivers, then rising up into healthier hill-country, the whole in its wild state hampering to human enterprise.

And below it occurs the grassland of the pampas, only needing the horse to bring out the powers of its native occupants.
Before leaving this subject of the domesticated horse, of which so much use has already been made in order to illustrate how geographic opportunity and human contrivance must help each other out, it is worth noticing how an invention can quickly revolutionize even that cultural life of the ruder races which is usually supposed to be quite hide-bound by immemorial custom.

When the Europeans first broke in upon the redskins of North America, they found them a people of hunters and fishers, it is true, but with agriculture as a second string everywhere east of the Mississippi as well as to the south, and on the whole sedentary, with villages scattered far apart; so that in pre-Conquest days they would seem to have been enjoying a large measure of security and peace.

The coming of the whites soon crowded them back upon themselves, disarranging the old boundaries.