The Influence of Salts in Rock Weatliering. 171 



(1) The hollowing out of cliffs of hard rocks abutting the " dry "■ 

 lakes, generally at or close to the base of such cliffs, thereby tend- 

 ing to keep the cliffs steep, and at the same time assist in their 

 recession ; and by such hollowing to aid in forming level rock floors 

 at the edge of the lake. 



(2) The disintegration on rock floors of lakes, whether close tO' 

 or at any distance from the cliffs, of the rocks forming such floors. 



Further research, particularly on the chemical side, is needed tO' 

 definitely substantiate these results. 



The mode in which the debris at the foot of and beneath the cliffs^ 

 and on the rock floors of the lakes, is removed, does not come with- 

 in the scope of this paper ; but in order to fully understand the 

 part played by " exsudation," brief mention must be made of the 

 processes following the breaking down of the rocks, and the effect 

 on the land forms. 



As already pointed out, the cliff's are broken down by rain, by 

 insolation and by " exsudation," these agents being helped by the 

 weakening of the rocks by meteoric waters acting as solvents. The 

 removal of the detritus is, in the opinion of the M^riter, chiefly due 

 to the wind acting in its deflative capacity, although the lapping 

 of the lake waters, when they collect after rain for a brief period, 

 may remove fine material in suspension, but this removal is often 

 counterbalanced by the deposition of the silt when the water dis- 

 appears. On the rock floors of the lakes the same principles apply. 

 The wind as a corrosive agent is also believed to act on the base of 

 the cliffs, and on the rock floors to some extent. 



The effect of such processes is to produce a cliff of varying steep- 

 ness, with a rock floor of such smoothness that the writer has 

 termed it a "billiard-table rock floor." The cliff recedes, and, 

 owing to various causes, is followed by the water. Thus a migra- 

 tion of the lake takes place.*! Such migration of cliffs and of lakes, 

 and the production of level rock floors, are materially aiding the 

 formation of a vast plain at a considerable height above sea level 

 as opposed to a normal peneplain, whose base level approximates tO' 

 that of the sea. 



ADDENDUM. 



Since this paper was read, Mr. F. Chapman, A.L.S., etc., of the 

 National Museum, Melbourne, has kindly drawn the writer's attention 

 to an interesting letter by Dr. F. A. Bather on salt weathering, in the 



1 The theory of lake mitrratioii in Western Australia has been first stated by the writer in his. 

 work already cited (pp. 155 57), and has been elaborated by him in a hitherto unpublished paper. 



