Davis.] 48 [May 3, 



C. 3. Cirques. The amphitheatres or cirques in which many 

 valleys head are often considered the peculiar work of ice ; but 

 the arguments in favor of this view are only that glaciers have 

 occupied the cirques, and that it is difficult to explain them in 

 any other way (see D). 



D. Mackintosh describes the " coums " of Wales, and thinks it possible 

 that ice might have cut them out, if it had a rotary motion; but that the 

 explanation of their origin will ultimately be found in some kind of action 

 midway between glacial and marine. (The Scenery of England and Wales, 

 1869, 194-204.) 



B. Gastaldi finally admitted the glacial origin of cirques, after at first 

 going only as far as required by de Mortillet's theory of the origin of the 

 Italian lakes. (On the Effects of Glacial Erosion in the Alpine Valleys, 

 Geol. Soc. Journ. xxix, 1873, 396-401.) 



J. J. Goodchild is "led to regard nearly all the more prominent rock- 

 features of these well glaciated parts (Yorkshire dales) as in one way or 

 another the result of glacial erosion," because of the difficulty of explaining 

 them in any other way. (Glacial Erosion, Geol. Mag. n, 1875, 362. See 

 also Geol. Soc. Journ. xxxi, 1875, 98.) In attempting to explain small 

 cirque-like hollows in Northern England, he says that the hypothesis that 

 they " are due to the eddying of the ice must be accepted until it can be 

 shown that this hypothesis is clearly disproved by any of the facts." He 

 supposes the rotary motion given to the ice as it is given to a river, by a 

 bend in its course or the entrance of a side stream. (On the Origin of 

 Coums, Geol. Mag. n, 1875, 497.) But no evidence of any such rotary 

 motion has been found for any of the well-studied existing or extinct glaciers 

 of Switzerland, in spite of their many branches and crooked valleys. It 

 would be interesting to inquire whether these peculiar valley forms (coums, 

 scars, etc.) are limited to regions known to have been glaciated. 



J. J. Stevenson attributes the form of trough-valleys and cirques to gla- 

 cial action. (Explorations and Surv. W. of 100th Merid. Geology, Wash- 

 ington, 1875,426-453.) 



J. F. Carll believes there may be different currents in the ice-sheet, one 

 above the other, but not parallel ; where two ice-currents met in the upper 

 Genesee valley, "an ice-eddy resulted, which cut out a broad basin and 

 deposited heavy masses of drift." "This action of the two currents is made 

 manifest both by the shape of the basin and by the position of the eddy 

 hills." He attributes some of the excavation of Lake Erie to the subgla- 

 cial streams. (Second Geol. Surv. Penn., Oil Regions, I 3, 1880, 333, 

 389, etc.) 



A peculiar comment on the above is made by S. A. Miller. (North Ameri- 

 can Mesozoic and Caenozoic Geol. and Pal., Cincinnati, 1881, 338.) 



