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Indiana University Studies 



Thruout Peru, Ecuador, and Colombia there are two main 

 chains of the Andes, the maritime, or western Cordilleras, ex- 

 tending from near Girardot to Cape Horn, and east of these the 

 older of the two called the White in Peru, Oriental in Ecuador, 

 and Central in Colombia. 



Peru. The physical features of western Peru are very simple. 

 The crests of the western Cordilleras form the divide between tha 

 Titicaca or Atlantic and the Pacific slope drainage. The crest 

 has an elevation of over 14,000 feet everywhere except inland 

 from Paita. Here a dip in the crest has an elevation of only 

 6,700 feet. 1 



In Peru the Pacific slope is drained by a large number of 

 rivers rising in the western Andes. After a comparatively shore 

 and very swift course they either empty into the ocean, or are 

 lost in the sands near the coast, or are more or less exhausted in 

 irrigation projects. Only one of the rivers has a north and south 

 trend for any considerable distance. This is the Rio Santa in 

 central Peru, which, in its upper course, flows between two 

 chains of the western Cordilleras. 



All of the rivers have a very great seasonal fluctuation. The 

 maximum flow in all the rivers occurs in March, the minimum in 

 late summer. 



The stretches between successive rivers on the Pacific slope of 

 Peru are, in most cases, bone dry deserts, or masses of moun- 

 tains, into which the rivers have cut deep gorges. These condi- 

 tions have mitigated against the ready intermigration of fishes. 



The Vitor river, in southern Peru, for instance, rises in an up- 

 land meadow (over 14,000 feet), flows thru a region of volcanic 

 ash, and has, in its middle course, a valley (Vitor Valle) about a 

 mile wide, cultivated to vines, figs, small fruits, and grain. Then 

 it falls to a lower level, near the coast, where there is another val- 

 ley. Looking from the hills about Yura, near Arequipa, toward 

 the ocean, the land is a billowy mass of arid, sand-drifted moun- 

 tains and plains, with nothing green visible anywhere. 



The Rimac has a somewhat different course. The Rimac 

 and its tributaries rise in small glacial lakes with elevations of 

 about 15,000 to 16,000 feet. They are, in part at least, inhabit- 



^nock (Peru, 1910, p. 11) says.: 



"The traveller who enters the interior of Peru from the Pacific Coast must invari- 

 ably cross the Andes at an altitude of 14,0GO feet or more, for the passes of the main 

 Cordillera all reach this elevation. There is one exception, in the northerly part of 

 the country, towards the frontier of Ecuador, where a low gap exists in the Andes, of 

 some 6,700 feet elevation: but this is the only exception in thousands of miles of con- 

 tinuous mountain chain." 



