124 /. T. Jutson: 



Various Possibilities considered as to the Origin of 

 certain of the described Features.^ 



The following remarks are offered with regard to the origin of 

 ihe rock cliffs and the various rock floors described above. 



(1) Fluviatile action seems to be incapable of producing these 

 features. The normal results are as stated by Holjbs, but here the 

 results are abnormal. In the longitudinal valleys of the high lands 

 where the rain becomes far more concentrated and, consequently, 

 has much stronger erosive power than have the waters on the lake 

 •(despite tlie presence of some vegetation in the valleys, and its 

 absence on the lake), there are normal fluviatile deposits (coarse 



•detritus and small flood plains a few feet thick). Hence, as this" 

 concentrated Avater cannot remove tlie detritus and produce rock 

 floors in tlie valleys, it seems impossible to account for the rock 

 floors of tlie lake by the action of diffused terrestial waters, the 

 function of which on flat areas is, so far as known, to deposit 

 •detritus rather than to remove it. 2 



(2) Marine action could produce steep rock cliffs, but billiard- 

 table floors are hardly to be expected in rocks of the character 

 •described; nor can marine action be considered as having pro- 

 duced the valley-like arms of the lake. Moreover, there is no evi- 

 •dence that the sea extended in recent geological times as far inland 

 as the area described. No marine fossils have been found, and 

 there is no occurrence of normal Avater-worn pel)bles, such as would 

 be expected if the cliffs w^ere attacked by the sea. 



(3) The erosive activity of former deep, permanent lakes might 

 produce cliffs, but rock benches and true gravels would be expected, 

 and these do not occur. 



(4) The wind remains to be considered. It is accepted by the 

 Avriter as the dominant agent of erosion. Its main activity is 



•deflation, as the actual breaking or wearing down of the rocks is 

 due to ordinary atmospheric weathering, the beating action of 

 rain, insolation, '' exsudation," and wind corrosion, but details 



■cannot be given here. In the removal of the detritus from the foot 

 of the cliffs, the lapping of the temporary lake Avaters no douV)t 

 in places assists. 



1 It is not proposed to deal with the origin of the lake as a whole. The "dry" lakes 

 occupy drainafife lines of the country, and therefore must he considered at least partly of fluviatile 

 •origin For the various theories of the origin of these lakes see the writings of H. P. Woodward, 

 A Montgomery, C. G. Gihson, J. W. Gregory, and the present writer. 



2 There are some ill-defined, very shallow water channels across portions of the lake floor 

 west of the main portion of the lake, but they would not have sufficient fall or scour to keep 

 the floors free from detritus. 



