EIVERS OF ARGENTINA. 373 



The E,ios Primero, Segundo, Tercero, Cuarto, and Quinto. 



The streams descending from the Cordoba heights eastwards to tlie pampas, 

 have been numbered rather than named in their order from north to south. The 

 Rio Primero, "First," transformed by a reservoir to a lake above Cordoba, almost 

 runs dry on entering the pampa, although after heavy rains its yellowish waters 

 reach the Mar Chiquita. The Rio Segundo, " Second," which follows a parallel 

 course farther south, also disappears in shallow depressions, which evaporate in the 

 sun. 



But the more copious Rio Tercero, " Third," maintains its current across the 

 pampa, although gradually changing from a fresh water to a saline stream. 

 Towards the middle of its course it receives the salt water of the Saladillo, which 

 appears to be fed by the infiltrations from the irrigation canals derived from the 

 Rio Cuarto, "Fourth." Before reaching the Parana, the Tercero, here called the 

 Carcarana, or Carcaranal, from an extinct Guarani tribe met by Cabot, is joined 

 by the Arroyo de las Tortugas, " Turtle Creek," which was perhaps at one time 

 the outlet of the Mar Chiquita. The Carcarana is accessible only to boats drawing 

 two or three feet. 



The Rio Quinto, " Fifth," rises not in the Cordoba uplands, but farther west 

 in the Sierra de San Luis, and the streams descending from the Cordoba slopes 

 fail to reach its banks. After a south-easterly course of 300 miles it runs out in 

 the Amarga, or "Bitter " lagoon, in a region of swamps and quagmires extremely 

 dangerous to wayfarers. These gnada/es, as they are called, long afforded a refuge 

 to the Ranquele Indians against the white invaders. 



Eastern Affluents of the Parana. — Lake Ibera. 



On its left bank the Parana receives the contributions only of a few small 

 affluents. In this Argentine " Mesopotamia," the surface is also so level that the 

 waters expand in swamps and lagoons, such as the Lake Ibera, " Brightwater," 

 which, perhaps, indicates the former channel of the Parana, when it flowed parallel 

 with the Uruguay. 



In this part of the region comprised between the two main streams the surface 

 stands almost at a dead level. Hence it was found possible to attempt to partly 

 drain the Ibera lagoon at two different points. At the head of the basin trenches 

 M'ere excavated for the purpose of carrying off the overflow to the upper Parana, 

 while lower down the rivers Batel and Corrientes were deepened and canalised, 

 and thus made to receive a portion of the discharge through some sluggish 

 channels. The Ibera lagoon has a total length of over 24 miles, with flat 

 uncertain margin on the west side, but sharply limited on the east side by steep 

 banks and hillocks, which rise to heights of from 30 to 50 feet above the surface 

 of the lake. The whole basin is disposed in a succession of esteras, most of which 

 are overgrown with forests of reeds, while others are deep enough to be navigated 

 by small craft. But few boatmen venture to ply on these waters, which are 

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