THE PARANA BASIN. 



209 



as the Rio Grande. About half of the Paranapaneraa basin, comprising some 

 30,000 square miles, still figures on the maps as the Zona descGuhcctda, the " Un- 

 known Zone." 



The Paranapanema, or " Useless River," as the word is interpreted by some 

 etymologists, fully deserves its name, so completely obstructed is its channel by 

 projecting reefs and rapids. At the present limit of navigation below the Rio 

 Purdo, occurs the Salt Grande, " Great Fall," where a volume of about 1,000 

 cubic feet per second is precipitated some 30 feet down to a seething chasm, 



Fig. 88. — Falls of the Paeanapanema. above and below S. Sebastiao. 



Scale 1 : 750,000. 



49°56' 



43'34- 



West or breenwicln 



2,200 Yards. 



whence the boiling waters escape through a narrow cleft in the rocks. Other 

 cascades follow, preventing all navigation down to the Tilbagy confluence, 

 whence the channel is free to its junction with the Parana, 850 feet above sea 

 level. 



Parallel with the Paranapanema, flow the Ivahy and Piquiry, joining the 

 great artery on the plateau above the point where it forces its way through the 

 Maracaju (Mbaracayu) ridge on the Paraguay frontier down to the plains. 



