144 PATAGONIA AND SHEEP-REARING 



from November to April. The routes they take are 

 not invariable. One of the most frequented, leading 

 from the sub-Andean tablelands to San Julian, follows 

 the Santa Cruz valley. When the land was cut up, 

 there was no reason to foresee these movements, and 

 nothing was done to facilitate them. The roads cross 

 the ranches, which are compelled to allow it. It is 

 a serious burden for some of them, unless they can make 

 a profit out of their situation on the road by hiring 

 pasture for the flocks as they pass. 



The Andean zone itself is still mainly pastoral, but 

 it is nevertheless far more varied and richer in possi- 

 bilities of development than the tableland. Agriculture 

 is already combined with breeding in that area. 



The name vegas, which in the Puna and at San Juan 

 means alpine pasture, is applied here to tilled patches 

 in the Andean valleys. They are found in the north 

 in the valley of the Neuquen, round Chosmalal. In 

 the south, the valley of the Rio Pico marks the limit 

 of cultivation. Irrigation is almost always necessary 

 north of Lake Nahuel Huapi, where the vegas have, 

 as a rule, a soil of coarse alluvia or permeable tufa, 

 which dries up quickly. Water is plentiful, it is true, 

 and increases in quantity rapidly as one travels south- 

 ward. The chief obstacle to the extension of cultivation 

 is the frequency of frost in spring and summer. The 

 deep hollows of the sub-Andean depression south of 

 Lake Nahuel Huapi, the height of which drops to 1,000 

 feet at the Bolson, and 1,600 feet at Diez y seis de 

 Octubre, have no frosts in summer, and they sustain 

 small agricultural communities. At higher levels, in 

 the basin of the lake or on the vegas of the Traful and 

 Lake Lacar, at an altitude of about 2,600 feet, the 

 distribution of the summer frosts is closely related to 

 the contour and lie of the land, which may facilitate 

 or impede the circulation of the layers of cold air, and 

 the play of what has been called atmospheric drainage. 

 The valleys which are very open from west to east, 



