THE CHIEF REGIONS 175 



remind us of the fresh circular dunes with a central 

 lagoon. The lines of coastal dunes in the eastern part 

 of the Buenos Aires province obstruct the proper flow 

 of the water there, and form a group apart, which 

 must be clearly distinguished from the dunes on the 

 plain. ^ 



Thus the impression of monotony which the Pampa 

 makes in us is corrected to some extent by close observa- 

 tion. High and low land alternate on it. Parchappe 

 himself had noticed the contrast between the area that 

 stretches from Buenos Aires to the Salado, with its 

 soft undulations and its well-developed hydrographic 

 network, the horizontal plains on the right bank of 

 the Salado, with their irregular dunes, and the southern 

 plateau of the tosca between the Sierra de Tandil and 

 the Sierra de la Ventana. 



We may now distinguish the following regions in 

 the Pampa as a whole : 



I. The central part of the Santa Fe province forms 

 what is called the district of the " colonies " : that 

 is to say, the domain of the colonies established two 

 generations ago, and the zone in which the type of 

 cultivation introduced by them took root. The chief 

 crops here are wheat and flax. Hedges of service trees 

 (paraisos) surround the fields. In contrast with the 

 parts of the Pampa which have remained naked, the 

 region of the colonies seems a veritable grove. It 



' Outside the districts with quick and dead dunes, a frequent type 

 of landscape on the Pampa is a plain thinly sown with very small 

 lagoons, generally circular, between which develop a series of barely 

 perceptible undulations. The inequality is at times so slight that 

 one only notices it by the contrast between the vegetation of the 

 lower and the higher ground. This type of landscape, which is 

 especially seen in the district of Lincoln or of Nueve de Julio, is due 

 to the action of the wind on a plain where the level of the under- 

 ground water is near the surface. This level marks a limit below 

 which aeolian erosion does not take place : a sort of base-level. The 

 periodic variations of level of the underground water reduce or en- 

 larges the undulations of the surface. 



