280 



SOUTH AMERICA— THE ANDES REGIONS. 



The deep valley separating the Cordillera Negra from the Cordillera Nevada 

 is commonly known as the Callejon ("Road," "Path") of Huaylas. It consists, 

 in fact, of a long guUey between two chains which seem quite distinct, but which 

 were formerly united in a single rampart. At the source of the Hio de Santa, 



Fig. 108. — Drainage Area of Huaylas. 

 Scale 1 : 1,500,000. 



where they have their common origin, it is easy to observe the cohesion at one 

 time presented by both geological formations, which became gradually separated 

 by the action of the snows, ice and running waters. The whole valley has been 

 excavated step by step, forming at first a series of lakes connected by a river 



