210 ROADS AND RAILWAYS 



other hand, an insurmountable obstacle, which diverts 

 southward the high road to Chile via Achiras, San 

 Jose, del Morro, and San Luis. 



The sierras of the Buenos Aires province are not so 

 high and extensive. They are, moreover, broken into 

 isolated hills with the plain passing between them. 

 As early as 1822 Colonel Garcia pointed out the 

 importance, in connection with the migrations of the 

 Indian tribes, of the passage between the Sierra 

 Amarilla and the Sierra de Curaco, that is to say, the 

 Olavarria ridge. It is there that the first railway 

 between Buenos Aires and Bahia Blanca crosses the 

 line of sierras. It then skirts the Sierra de la Ventana, 

 to the north, by the Pigiie ridge, between the mass 

 of Curumalan and the Puan hills. The dunes of the 

 western Pampa also are an impediment to traffic, not 

 so much because of their height as because of the 

 looseness of the ground. The strip between General 

 Acha and Toay was very trying for the stage-coaches. 

 Travellers had to cross the dunes on foot during 

 the winter season, when the horses were in a bad 

 condition.^ 



Natural supplies of water increase in number as 

 one gets away from the Andean zone toward the east. 

 Still, the chief work, often the only work, to be done 

 in making a road is the arrangement of permanent 

 supplies of water. Martin de Moussy mentions the 

 digging of wells on the new road from Cordoba to 

 Rosario, which was opened about i860. The aiguade 

 was generally a represa, a reservoir, where the water 

 accumulated behind a barrier of earth raised across 

 the course of an intermittent stream. The upkeep of 

 the represa is the chief duty of the post-master. The 

 edge of the sierras and the opening point of the ravines 

 which come down them is a good place for making 

 represas, and the roads frequently keep to these (variant 



» J. B. Ambrosetti, " Vi^je a la Pampa central," Bol. Instit. Geog. 

 Argent., xiv. 1893, pp. 292-368. 



