[Proc. Koy. Soc. Victoria, 30 (N.S.), Pt. II., 1918]. 



Akt. XVII. — The Influence of Salts in Rock Weathering in 

 Sub-arid Western Australia} 



By J. T. JUTSON. 



(Geological Survey of Western Australia). 



(With Plate XXX.). 



[Read 13th December, 1917J. 



Intpoduction. 



Among the many erosion processes that are now acting in that 

 portion of sub-arid, south-central Western Australia, which corre- 

 sponds with the writer's Salt Lake or Central physiographic divi- 

 sion, 2 the apparent influence of the crystallization of salts under 

 certain conditions in breaking up the rocks and in assisting to 

 give characteristic forms to certain features of the landscape, has 

 not hitherto been recorded. This phase was first pointed out to 

 the writer at Lake Raeside, which lies chiefly to the east of the 

 railway running north from Kalgoorlie through Menzies and 

 Kookynie,^ by Professor J. Walther in 1914, on the occasion of the 

 visit to Australia of the members of the British Association for the 

 Advancement of Science. This process of erosion may be regarded 

 as one of the phases of " exsudation," a term which is subsequently 

 defined. Since the visit referred to, the writer has studied the 

 question in the field in several localities, and now submits a brief 

 account of the process and its effect in modifying the land surface. 



Situations Favourable for the Wopk of " Exsudation." 



"Exsudation," as understood in this paper, can only be ob- 

 served taking place in certain comparatively limited situations 

 These are as follow : On tlie face, but most frequently close to the 

 bottom of the cliffs bounding the "dry" or "salt" lakes; on 

 the rock floors of such lakes; possibly in hollows beneath the hard 

 caps of lines of cliffs known as " breakaways," (which may border 



1 By permission of the Direntor of the Geological Survey of Western Australia. 

 •2 Jutson, J. T.^An Outline of the Phf/siofjiaphicnl Gfolocin (Plnixionraphy) of Western 

 histralia. Bulletin 61 of the Geol. Snrv. Western Australia, pp. 32 and .5-2. 

 3 .Menzies is 80 miles and Kook^\nie IIS miles north of Kalyoorlie. 



