Features and Groivth of Lake Goovgarrie. 125- 



Reasons for Acceptance of the Wind Theory. 



(1) The elimination of other possible agents as shown above. 



(2) The occurrence of rock cliffs and rock floors on the westerm 

 side, and their absence on tlie eastern side of Lake Goongarrie and 

 of numerous other "dry" lakes; the impossibility of explaining- 

 these features by the fluviatile, marine, or deep permanent lake- 

 theories; and the fact that such lakes appear to be migrating west- 

 ward. 



(.3) The ignoring in the marine and deep permanent lake 

 theories of the present erosinal processes. 



(4) The passage of the piedmont plains into lower-lying bed- 

 rock floors, and the truncation in places of such piedmont plains- 

 into low cliffs. 



(5) The occurrence of rock basins. Solutions appears to be tlie 

 only alternative to wind erosion for these basins, and it does not 

 seem to apply. 



(6) The relations of the sand ridges, of the arms, and of the 

 lowlands to one another. 



Origin of the Rock Basins. 



As true rock basins seem to exist, they can only have been pro- 

 duced either (a) by the wind in its defiative capacity acting on the- 

 products of unequal weathering or in its corrosive and defiative 

 capacities, or by a combination of all three methods, or (b) by^ 

 solution. There are no grounds for believing that solution is act- 

 ing differentially, so that the wind in one of the three modes sug- 

 gested is apparently responsible. The shallowness of the basins' 

 and their partial filling by fine aqueous silts (which are apparently" 

 due to rain), are in accoi-d with the generalization enunciated by 

 Passarge^ and adopted by Davis, 2 as to the influence of rain in 

 preventing the formation oT deep wind hollows. 



The Relations between the Sand Ridges, Lake Arms 

 and " Lowlands." 



The low cliffs forming the western boundary of the lowlands are 

 furrowed and cut back by rain, and fron; their base ill-defined 

 stream courses, a few feet wide and a foot or two deep, extend 

 eastward down the gentle slopes which are covered by a layer, prob- 



1 Zeit. der Deufc. jfeol. Gesell., 56 Band, iv., Heft, 1904, p. 20 



2 Geo;fraj)hical Kssays, p. 307. 



