550 PEHR OLSSON-SEFFER 



fine material needed to supply plants with soluble substances, and 

 thus to allow a cover of vegetation to gain a foothold. 



The action of wind as a transporting agent when removing the 

 denuded rock material, whether soluble or insoluble, as soon as it 

 appears at the surface is one of the most important factors in the 

 denudation processes. Walther' calls this phenomenon deflation 

 and he considers it to be of even more consequence than abrasion. 

 Through deflation fresh rock is consequently exposed to the eroding 

 forces, and it is evident that this action must be considerable, especially 

 on the coasts with their moist climate. 



The softer strata of rocks are worn more deeply by deflation, co- 



FlG. I. — Established and rejuvenated dune surface at Fremantle, Western Aus- 

 tralia. 



operating with abrasion, and the harder layers are left to form cornices. 

 On account of the abrasion being greater near the surface where the 

 wind current carries a greater load of sand, the lower parts of rocks 

 are often eroded more rapidly than the upper. Evidence of this 

 can be seen in the "balancing rocks" not infrequently occurring in the 

 neighborhood of extensive sand formations. The writer has seen such 

 rocks on many coastal sands, near Port Fairy in Victoria, for instance, 

 on the West Austrahan coast, at Port Said in Egypt, and at Carmel 

 Bay in California. 



It is especially the fine particles of sand which are liable to be 

 transported by the wind ; but as the fine sand retains its moisture better 



I Das Gesetz der Wustenbildung, 1900. 



