15G 



AMAZONIA AND LA PLATA. 



and then to the east, and before reaching the ocean even turns to the south-east, 

 after descending from the inland plateaux over the superb Paulo Affonso Falls. 



Even near its source in the Serra da Canastra, the S. Francisco develops a cas- 

 cade to which Saint-Hilaire, confounding it with another, has wrongly given the 

 name of Casca d'Anta. Fescending to the lower valley through a succession of 

 cscadinhas or "steps," it is joined on the right by the Para, and farther on by the 

 much more copious Paraopeba, which collects the surface waters in the south-eastern 

 part of the basin. At this confluence the united streams have already a discharge 

 of over 7,000 cubic feet per second, while the level is raised during the floods to 

 from 26 to 40 feet according to the seasons. Thus are formed numerous swampy 



Fig. 59. — Sapâo and Somno Watershed. 

 Scale 1 : 5,300,000. 



1-25 Miles. 



and malarious tracts, whose noxious exhalations even affect swine after the inunda- 

 tions. 



The Eio das Yelhas (Guaicuhy), chief affluent of the Upper S. Francisco, 

 descends from the Queluz heights in the mining district, and contributes on an 

 average over 7,000 cu.bic feet per second to the main stream. The Velhas is 

 partly fed by underground streams carrying off the overflow of the numerous 

 reservoirs in the cave district. The Lagoa de Sumidouro, one of the subter- 

 ranean lakes, is alternately flooded and empty according to the rainy and dry 

 seasons. 



Below the Yelhas confluence, the S. Francisco flows in a broad, deep channel, 

 navigable by large craft throughout the year. Here it is joined by several 

 copious affluents, also navigable in their lower courses — the Paracatu (" White 

 River "), the Urucuia, and the Carinhanha from the west, and from the east 



