1849.] AUSTEN ON THE VALLEY OF THE ENGLISH CHANNEL. 71 



on the other, according to what is to be observed in every valley of 

 fracture. Whether this supposition respecting the valley of the 

 Seine be correct or not, we at least meet with features on our own 

 coast which make it probable. Thus, for instance, the vertical cliffs 

 of the Watcombe fault have certainly been produced since the district 

 existed in its present condition of dry land : the direction of this 

 break is east and west. Again, Torbay, which is a portion of an east 

 and west depression, has its recent age defined by the marine beds 

 resting on the lines of elevation which bound it. 



So much has been written respecting the quantity of matter carried 

 down annually to the sea by rivers, that many have been led to regard 

 it as the main source of submarine sediment : the English Channel is 

 perhaps as good an instance as could be taken of the fallacy of such 

 a supposition. The Seine is the only river of any magnitude which 

 discharges into it. Now rivers carry forward matter in two ways — • 

 by holding it in suspension, and by drifting it along their beds. 

 The quantity of suspended matter in the estuary portion of such a 

 river as the Seine is occasionally considerable ; but it is an incon- 

 siderable portion of this only which finds its way out to sea at each 

 ebb ; whilst the sands which are subject to the drifting process ac- 

 cumulate in well-defined forms about its mouth. If we take the 

 whole extent of the dry land drained by the rivers running into the 

 English Channel, together with its mean elevation, we shall see that 

 the whole of this mass, if removed down to the sea level, would be 

 insufficient to fill up that depression. We may feel assured that the 

 joint action of all the Channel rivers contributes but very little towards 

 its accumulations. On comparing some old charts of the mouth of 

 the Thames with the most recent ones, the principal feature in which 

 they seemed to differ, was the present outward extension of the shoals 

 and banks. 



Sir H. De la Beche has treated of the action of the sea along its 

 coast-line in full detail ; it is this line which furnishes the great mass 

 of materials we find strewed over its beds. To show that it is an 

 adequate source, we have only to bear in mind, that in the instance of 

 the area of the English Channel, if we follow its irregularities, we 

 have an outline of not less than 1 200 to 1 300 miles, together with a 

 great vertical range of tide. The removal of solid materials from the 

 cliffs is not, however, so constant as some persons might imagine, not 

 even on parts of the coast with yielding strata. There are very few 

 places on our own side of the Channel, or on that of France, at 

 which the sea at high-water regularly reaches the bases of the cliffs, 

 and where it does so, from the hardness of the rocks, the rate of 

 destruction is the slowest. x\s a general rule, it is only with high 

 tides, concurrently with gales of wind setting on a given line of coast, 

 that we see any considerable masses undermined and thrown down. 

 If this be the case in such a sea as the Channel, where the power of 

 the breakers is exhibited on so vast a scale, it teaches us to require 

 enormous lapses of time for the production of sedimentary strata of 

 the thickness of some of those for which the geologist has to account. 



But though the sea for months together, and in places even for 



