168 SOUTH AMERICA 



passes to the alpine belt of sparsely clotted dry, dwarf 

 plants. 



The Peruvian Andes was once the seat of a powerful 

 and advanced civilization which flourished until the 

 Spanish conquests of the sixteenth century; now im- 

 pressive ruins are the only traces to be found. Agriculture, 

 with irrigation and manuring, was then brought to a 

 point of perfection which has not been equalled since 

 in that region ; but large areas which had been under 

 cultivation now lie desolate, claimed by the desert. The 

 prosperous cities which lined the shore, nestled in the 

 valleys, or expanded on the plateaus, have fallen into 

 ruins. There is no doubt that in the times of the Incas, 

 Quichuas and Aymaras, before the advent of Europeans, 

 the belts of vegetation and cultivation were broader on 

 the Pacific slopes than they are now, which may be due 

 either to better climatic conditions or to artificial irriga- 

 tion, or to both. 



Atacama. About the latitude of 20° S., the rapid 

 declivities of the coastal ranges give way to a succession 

 of broad terraces broken by ranges and rising in steps 

 towards the top plateaus of Bolivia. This region is 

 practically an absolute desert the soil of which is 

 impregnated and covered with alkalis, perhaps the 

 barest place of the tropical world. Human habitations 

 are entirely confined to the coast, where water can be 

 had by boring, and a few straggling trees and sage-bushes 

 and mesquites are occasionally met with. From terrace 

 to terrace, and up the naked scarps, the desert rises to 

 above 10,000 feet, only to merge into the scarcely less 

 dreary inland punas. Yet it is from those very deserts 

 that one of the most valuable fertilizers — nitrates — is 

 extracted and shipped to the whole world. 



Central Chile. By Caldera, the desert proper stops, 



