SCARCITY OF FRESH WATER 141 



and for shearing. These incessant movements toward 

 the centre of the ranch cause an almost permanent 

 strain on the pasture, and this is one of the chief anxieties 

 of the breeder. The area of the estate is divided as 

 soon as possible into sections (potreros) by steel-wire 

 fences, which enables them to watch over the repro- 

 duction and improvement of the flock and make the 

 best use of the pasture. Fencing is more advanced 

 near the Cordillera, as timber for the posts is found 

 there. 



Certain districts are still uninhabited on account 

 of the lack of water. Some of the sources of water are 

 permanent. The water issues at the base of the vol- 

 canic rocks, when the underlying rock is impermeable, 

 and above the various levels of the marl in the 

 Patagonian swamps ; for instance, in the cafiadones 

 round the Gulf of San Jorge. Besides this, the rain 

 and melting snow leave on the surface of the table- 

 land a great number of pools, which evaporate in the 

 dry season. These are temporary supplies, the 

 manantiales , to which the breeders are reduced over 

 large areas of the tableland. Most of the stagnant 

 sheets of water which are permanent are saline. The 

 proportion of salt in them is very variable, and changes 

 in each case according to the cycle of dry and wet 

 years. The water of the Carilaufquen was fresh in 

 1900, and in 1914 it had become brackish, though 

 it could still be used for the flocks. 



Finding permanent sources of water is the first concern 

 of the breeder. In some districts he has succeeded in 

 tapping sheets of fresh water by means of wells. There 

 are none of these wells in the crystalline zones, the 

 closed hollows, where the sheets of water are often 

 large, but they are always saline. Neither are there 

 any in the red sandstone district, the dryest of all. 

 In the western region the wells are sunk in the arid 

 valleys, along the track of the underground stream. 

 Thus the Picun Leufu, the visible course of which is 



