18 NATURAL REGIONS OF ARGENTINA 



a foreigner, an emissary from tropical America ; for it 

 has a flora of its own and tepid waters which often 

 cause a fog over the estuary where they mingle with 

 the waters of the sea. 



From the general mass of the Argentine plains, we 

 must set apart the region between the Parana and 

 the Uruguay, which Argentinians call " Mesopotamia." 

 While aeolian clays form the soil of the Pampa on the 

 right bank of the Parana, fluvial deposits — sands and 

 gravel, in which it is impossible to distinguish the 

 contribution of the Uruguay from that of the Parana — 

 cover a great part of Mesopotamia. The earlier beds 

 of the rivers may be traced here, not only by the alluvial 

 deposits they have left, but by the lagoons which still 

 mark their course. Running waters have shaped the 

 landscape and scooped out a system of secondary valleys, 

 and these reflect the history of the river itself and the 

 variations of base-level which led to alternate periods 

 of erosion and deposit. 



On the right bank, on the contrary, the Parana 

 has no tributaries of any importance except at the 

 extreme north of the country. The scarcity of running 

 water is, in fact, one of the characteristic features 

 of the plain of the Pampas. Except in the east, along 

 the Parana, where a network of permanent streams 

 develops on a comparatively impermeable and fairly 

 humid soil, and except at the foot of the mountains, 

 where irregular torrents and streams, swollen after 

 a storm and scanty in the dry season, disappear, as a 

 rule, within sight of the hills that gave them birth, 

 there is no superficial organized drainage. As a whole, 

 the alluvial covering of the Pampas, the upper beds 

 of which are cut through by the barranca of the 

 Parana, is not of river origin ; it was brought and 

 distributed by the wind, which took the place of running 

 water. The clay of the Pampas is a present from 

 the winds. The increasing dryness of the climate 

 toward the west, as one approaches the Cordillera, 



