124 PATAGONIA AND SHEEP-REARING 



done this with the terraces of the Limay. The Tertiary 

 marine deposits of the coast region also are rich in 

 pebbles torn from the rocky promontories of the shore ; 

 hence the extent of stony soils in the coast region. 

 The wind similarly strips naked the angular stones, 

 of local origin and incompletely worn, round the isolated 

 rocks of the desert tableland or on the flanks of the 

 secondary ravines. 



On the other hand, the bedding action of the wind 

 creates deposits consisting of small and uniform elements 

 from the sands of the dunes to the finest dust. The 

 lightest particles, caught up repeatedly by the squalls 

 and carried to a great height in the atmosphere, go 

 beyond the Patagonian region and reach the bottom of 

 the Atlantic or the plain of the Pampa. Some of this, 

 however, is deposited in the depressions of the table- 

 land, where the moisture fixes it and prevents the 

 wind from regaining it. These seolian deposits in the 

 depressions, a dark-grey clay, which hardens when 

 it is dry, but is softened by water, form two entirely 

 different kinds of soil. If the depression is closed in, 

 or if the circulation of the water is too slight, there is 

 a concentration of the mineral salts ; this is the salitral, 

 either naked or sustaining a halophytic vegetation, 

 which the saline efflorescences cover with a white 

 coat during the dry season. If on the other hand, the 

 underground waters have a free course, the seolian clay 

 forms the mallin. Bushes and fine grasses grow on 

 it, and, as they decay, gradually give it a darker shade 

 and modify its composition. The soil above the mallin 

 is rich in organic elements. It covers the bottom of 

 the valleys between low terraces, covered with faceted 

 pebbles, and dominated by the vertical cliffs of tufa 

 and lava. The contrast between the verdure of the 

 mallin and the arid, dusty, yellow steppe of the table- 

 land is one of the most characteristic features of 

 Patagonian scenery. The area in which mallin has 

 been formed coincides with the most humid districts 



