Geological Society, 293 



France, or from any other physical region on the surface of the 

 earth. 



The power of mountain torrents in transporting heavy masses of 

 stone is strikingly illustrated in a short paper by Mr. Culley. He 

 states that a small rivulet, descending from the Cheviot Hills along 

 a moderate declivity, carried down, during a single flood, many 

 thousand tons of gravel into the plains below; and that several 

 blocks, from one half to three-quarters of a ton weight each, were 

 propelled two miles in the direction of the stream. Facts, similar 

 in kind, but on a scale incomparably greater, must be in the recol- 

 lection of every one who has seen the Alpine torrents descending 

 into the plains of the north of Italy. 



When mountain chains abut in the sea, the laws of degradation 

 are not suspended. At each successive flood, fragments of rock 

 are drifted in the direction of the descending torrents, and rolled 

 beneath the waters. This kind of action is indeed casual and in- 

 terrupted ; but it is aided by another action which is liable to no 

 intermission — the beating of the surf and the grinding of the tidal 

 currents on all the projecting parts of a steep and rocky shore. 

 Under such conditions, I doubt not that there are now forming at 

 the bottom of the sea, and at depths perhaps inaccessible, alter- 

 nating masses of silt, and sand, and gravel, which, if ever lifted 

 above the waters, may rival in magnitude some of the conglomerates 

 of our older formations. 



Our last Paper, on the excavating power of rivers, was from the 

 pen of Mr. Scrope. He contends that diluvial torrents would only 

 form trough-shaped channels, extending in the direction of the 

 principal rush of water ; but would never produce curves in which 

 the excavating force worked in a direction opposed to that of the 

 general current. He describes part of the course of the Moselle 

 and of the Meuse, where the rivers wind through hard transition 

 rocks, in long sinuous channels, varying in depth from 500 to 1000 

 feet. In one of the great flexures of the Moselle, the river, after 

 passing over no less than 17 miles, returns to within 500 yards of 

 the point from which it started. These phaenomena are regarded 

 by the Author as sure indications of slow fluviatile erosion. For he 

 considers the idea of a great debacle, or diluvial current, winding 

 its way back in lazy flexures towards the point from which it 

 started, as absolutely unintelligible. 



If I might give my own opinion on this debated question, I 

 should say, that the existing river drainage of our physical region, 

 is a coiiii)lcx result, depending upon many conditions — the time 

 when the region first became dry land — its external form at the 

 time of its first elevation above the sea — and all the successive 

 disturbing forces which have since acted upon its surface. liut 

 none of these elements are constant: no wonder, then, that results 

 derived from distant parts of the earth should be so greatly in con- 

 flict with each other. In the formation of valleys there is therefore 

 little wisdom in attributing every thing to the action of one modi- 

 fying 



