366 R. Chambers, Esq., on Glacial Phenomena 



over surfaces beneath the sea level, thus producing upon the 

 subjacent rock those phenomena of rounding, furrowing, 

 and scratching, which have been attributed to the action of 

 ice. Such a process, Mr Mallet conceives, may be going on 

 beneath the sea, even at the present day. The only re- 

 mark I feel called upon to make regarding this theory is, 

 that, while few would deny that a mud-slide, land-slip, or 

 other slipping of detrital matter, is competent, when it takes 

 place, to abrade and scratch the subjacent faces of rock, the 

 phenomena really to be accounted for — the extensive denu- 

 dations, the abrasion of mountains and valleys in directions 

 irrespective of the inclination of the ground, and the deposit 

 of detrital accumulations over enormous surfaces with no 

 general slope at all (as the valley between the Friths of Clyde 

 and Forth) — are wholly beyond the imaginable scope of such 

 an operation. 



While thus sensible of how far any existing theory is from 

 accounting for the whole phenomena, I am by no means pos- 

 sessed of any theory of my own, which I think fit to be imme- 

 diately accepted and maintained, without future change or 

 modification. I can only say that it seems to me unavoidable, 

 that we suppose a mass of ice to have spread out, from the 

 north generally to the south, ice viscous and moveable like 

 that of subaerial glaciers, and like them sufficiently compact 

 to possess great abrading force ; and water has been con- 

 cerned in connection with this ice, as evidenced by the cha- 

 racter of the connected deposit of boulder clay ; but as to 

 the formation and movement of this supposed northern en- 

 velope, we are not yet in a position to speak positively. All 

 we can do is to enter upon a few speculations in connection 

 with these questions. 



What will most likely be felt as the great difficulty, is the 

 difference between the valley containing a modern glacier, 

 attended as it is by a mean inclination of three, four, or more 

 degrees, and a wide extent of country without retaining walls, 

 and with only certain inequalities throughout its surface. We 

 see, it will be said, how gravitation will produce a flow in the 

 one case, but not in the other. The difficulty, after all, will 

 be found to rest chiefly on this supposed necessity for the force 



