THE CLIMATE OF PATAGONIA 121 



Atlantic coast the winter-rain feature is less regular 

 and uniform. At San Antonio the heaviest rains fall 

 in autumn (April and May). There is a secondary 

 maximum in August, and a few more showers in the 

 spring (September and October). South of San Antonio 

 the winter maximum, which is always marked, is cut 

 by a short dry period (July and August at Camerones, 

 June at Deseado and Santa Cruz). 1 In the interior, 

 on the other hand, the winter-rain system remains 

 unchanged. The predominance of the precipitations 

 of the cold season is of great importance to the breeders. 

 As a rule, they come down in the form of snow, which 

 melts slowly, and the small quantity of moisture is 

 at least all absorbed in the soil. South of the Santa 

 Cruz the humidity increases, but the rainy season alters. 

 At Gallegos the wettest month is December ; at 

 Ushuaia, the rains last from September to March. 

 The snow-season (May-August) is the dry season, and 

 the snowfalls are not heavy enough to interfere with 

 breeding. 



The surface of the Patagonian tableland is very 

 uneven, though it bears traces of having been much 

 worn by the agencies of its desert climate, which seems 

 to have lasted through the whole Tertiary Era. Going 

 up the Rio Negro, one sees the grey sandstones and 

 Tertiary tufas which form the cliffs, on both sides of 

 the lower valley. They give place higher up to the 

 variegated marls and red sandstones of the Cretaceous 

 which form the tableland at the foot of the first Andean 

 chains. The core of ancient granites and porphyries 

 crops up at places from under the mantle of Cretaceous 

 and Tertiary sandstones. The horizon of the pene- 

 plain passes from the Tertiary and Cretaceous tableland 

 to level masses of crystalline rock, the contour of which 



1 This anomaly is doubtless due to the proximity of the sea and 

 the respite of the westerly winds in winter. The coast, with its cold 

 waters and the land-winds causing the deeper water to rise, has a 

 special climate of fogs and mists. These, which remind us of the garuas 

 of the coast of Peru, do not penetrate into the interior. 



