HYDROGEAPHY OF CHILI. 



429 



frontiers. Such is the Rio Sama, which since 1892 forms the boundary between 

 Peru and Chili ; the Rio Camarones, whose valley is still claimed by Peru ; the 

 Rio Loa, formerly the common frontier between Peru and Bolivia ; the Rio Paposa, 

 which before the treaty of 1883 formed the southern boundary of Bolivia. 



Flowing beneath more humid skies, the Huasco is copious enough to reach the 

 sea, from which, however, it is at times separated by a strip of sands. The Rio 

 Coquimbo (river of Elqui), which is tapped b}^ an irrigation canal, and the 



Fig-. 164. — Rio Laja and Biobio Confluence — View taken opposite San Rosendo. 



Limari also struggle intermittently seawards. But the first two really perma- 

 nent rivers of Chili are the Choapa and the Aconcagua, which are fed by the 

 snows of the two loftiest mountains in South America. Farther south the Maipo, 

 flowing well within the rainy zone, and receiving the contributions of the torrent 

 descending from Santiago, assumes the character of a fully developed stream. 



The Rap el, Maule and Cauten. 



All the rivers following southwards as far as the Strait of Chacao continu- 

 ally increase their volume in proportion to the extent of their basins, a fact 



