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 of a given size varies from place to place according to the rich- ness of the pastures, the degree of dissection of the relief, the access to water supply, and the distance from consuming cen- ters and the railway. Yet still the generalization holds true that, speaking roughly, all of the land is useful.

, 117—The high plateau, or altiplano, of Bolivia between Lake Titicaca and La Paz, looking eastward from a point near Viacha toward the Cordillera Real, The whole plain is intensively cultivated except where it is too gravelly or stony in belts and patches near the mountains.

On the east is the tropical forest, and on the west of the Peruvian and Bolivian cordilleras is the coastal desert; and in both these environments the usefulness of the land and the disposition of the settlements are in marked contrast to the conditions we have sketched above. The forest has natural pathways in the rivers that thread it, the so-called ‘flowing roads,’ so that men are driven to seek favorable settlements upon the river border. Strikingly similar are the disposition of settlements in the desert, where men seek the river though the interfluves are open, for the latter are dry and are areas of transit, not sources of livelihood, and it is on the valley floor