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 migration and unity is the prevailing north-and-south trend of the Pyrenean valleys which encouraged communication between France and Spain and thus gave the mountain zone itself, for the pasture and for the food it contained, an impor- tance not merely local or regional in character. It is only in our time, with through transportation in mind, that the Pyrenees have been looked upon as a barrier. In short, what is a home for the simpler civilization of yesterday may be a barrier for the highly developed civilization of today, which requires organization, government, transportation, access to world markets in a way and on a scale unknown to the primitive possessor of the soil.

The Puna de Atacama gains in geographical importance to the degree that it is studied as a part of the whole belt of high country that runs southward along the ‘Andean Cordillera through Peru, Bolivia, and northern Chile. The mountain folk of this region live under unlike conditions of climate, relief, trails, and markets; but all are alike in working at amazingly great altitudes and under primitive conditions that call always for intelligent and often for painstaking adaptation. ‘The physi- cal differences which the high country displays from place to place are reflected in the life and welfare of the various Indian communities. To conclude this chapter we shall now explore the conditions in certain more northerly districts in order the better to see the operation of physical handicaps that grow gradually more difficult in a southerly direction until they reach their climax in the bleak, cold, and arid Puna de Ata- cama where even the shepherds are driven out in winter at altitudes at which agriculture and cities flourish in Bolivia and central and southern Peru,

In Peru and Bolivia as far south as Uyuni (latitude 20° S.) the plateau and valley country between the eastern and western cordilleras has sufficient rain to make possible the cultivation of alluvial and hillside soils without irrigation, though irrigation is practiced throughout the whole of the