﻿Eigenman n : South America West of the Maracaibo 7 



ed by an Orestias. Then there is a descent of a few thousand 

 feet, with very swift water, not suitable for fishes, where we found 

 nothing. Within this belt streams are clear in the morning; in 

 the afternoon the melting of frozen ground rolls down thin mud 

 in which nothing can live. 



Between Rio Blanco and Lima, a distance in a straight line of 

 less than 50 miles, the river has a fall of over 9,000 feet. At 

 Chosica it has an annual fluctuation between a minimum of 10 

 cubic meters per second, in September, and a maximum of 115 

 cubic meters per second, in March. 



The Jequetepeque in northern Peru, with a total length of 

 about 75 miles, has a more gentle slope than the Rimac, having 

 a minimum flow of about 5 cubic meters per second in Septem- 

 ber and a maximum of 220 in March. 



The Piura river, at Piura, is reduced during the dry season to 

 a few stagnant pools in which the fishes become greatly concen- 

 trated. They starve, but some of them succeed in living thru the 

 dry season. 



In southern Peru the interandean region is occupied by Lake 

 Titicaca. In northern Peru it is drained by longitudinal rivers 

 which, in the north, turn eastward and empty into the Atlantic. 

 As stated above, thru the whole of Peru, and northward to the 

 Tumbez, the divide between the Pacific and eastern drainage fol- 

 lows the crest of the western Cordilleras. 



Ecuador. In Ecuador the crests of the two main chains of 

 the Cordilleras are but a few miles apart and are joined by cross 

 ridges, in part old lava fields, which divide the area between 

 them into a series of highland parks, 6,000 to 10,000 feet high. 

 Some of the parks drain into the Pacific, others into the Atlantic. 

 The continental divide thus lies along the crest of the eastern 

 chain from Popayan in southern Colombia as far as Cotopaxi in 

 northern Ecuador. It then shifts westward to the crest of the 

 western Cordilleras, then to the eastern Cordilleras again, then 

 to the western again, to the eastern once more, finally shifting to 

 the western crests, where it remains, thru all of Peru to southern 

 Chili. 



It may be questioned whether the northern parks of Ecuador 

 are drained into the Pacific because the heavy rainfall has en- 

 abled the Patia and the tributaries of the Esmeraldas to cut back 

 thru the western Cordilleras and thus to annex the interandean 

 streams, 2 or whether the present trend of these interandean rivers 



2 Both north and south of this area the interandean parks drain into the Atlantic. 



