﻿Rev. T. Q. Bonney — Formation of Cirques. 275 



limine that I cannot admit a necessary connexion between cii'ques 

 and glaciers, because I see no possibility of drawing any hard and 

 fast line between cirques, corries, and even the ordinary bowl-shaped 

 heads of valleys so common in any country which has been sub- 

 jected to meteoric action. The small passes into the large, the slope 

 steepens into the precipice ; but rain rills before they gather into a 

 streamlet, streamlets before they gather into a river, all produce 

 the same result ; viz. a bowl-like excavation in the mountain-side, 

 which is drained by the one outlet valley. I have even seen cirques 

 on clayey banks, in miniature, with walls that might almost be 

 measured by inches. Connecting links may be found, through 

 corrie and cwm, between the merest bowl-like hollow on some 

 down of Chalk or Oolite or even some plateau of sandy clay, and 

 the grandest cirque of the Alps or Pyrenees, The differences are 

 due to the nature of the materials and to other local circumstances. 



Besides the above, the following objections seem to me to make 

 Mr. Helland's hypothesis nntenable. 



1. The general smoothness of the rock in the bed of cirques and 

 corries. Where I have seen the live rock in the bed of a cirque or 

 corrie, it is usually smooth and iceworn. Were it formed as Mr. 

 Helland supposes, it should be always rough, — pitted with the 

 sockets of the extracted rocky teeth, — because it is deepened, not by 

 the wearing away of prominences, but by the fracture of fragments. 

 The sharp-edged blocks of which he speaks, so far as I have seen 

 them, are generally loose and strewn over the basin, i.e. they have 

 either fallen directly from above or been dropped by the melting 

 glacier. 



2. His theory fails satisfactorily to account for the tarns in certain 

 cirques when they are true rock-basins. " It does not seem likely 

 that they were mainly scooped out like the great lakes, along the 

 sides of which we see groovings and roches moutonnees one beside 

 the other ; for in the little lakes one often sees sharp-edged blocks 

 covering the bottom. When the glaciers of the cirques filled these 

 small lakes so as to leave but little water, it seems probable that the 

 water thus left would freeze in winter, so that the whole tarn 

 would be frozen to the bottom, and the rocks in that way broken 

 loose. Whatever may be the manner in which these blocks are 

 broken out, we see that, from their situation and form, a bursting has 

 taken place in these tarns, so that they are the last works of the 

 glaciers in the cirques." I quite agree with the final clause ; but 

 think that the rest — that the existence of the tarn before its basin — ■ 

 is rather like " seeing the roads before they were made." These tarns 

 are in fact among the basins which 1 readily concede to glacier 

 action, because, if a small glacier forms in a previously existing 

 corrie or cirque, the descent of the ice from the steep surrounding 

 slopes on to the level floor will facilitate erosion; so this is just 

 where I should expect to find — and commonly do find — a basin ; 

 but I have seen true cirques without tarns. The floors also of these 

 basins, as stated above, where visible, are smooth and iceworn. 

 Further, as these basins appear to be sometimes of considerable 



