1849.] AUSTEN ON THE VALLEY OF THE ENGLISH CHANNEL, 8S 



chronous series, of which every portion has been derived from one 

 common source — the coast-hne. At particular places, in sections 

 taken through them, masses of one set of materials would be found 

 resting on another, as sands upon marls, and gravels upon sands ; 

 and we might find these sands dipping away as a mass from the one, 

 and passing at the distance of a few miles beneath the other, as in 

 section fig. 2 ; yet the only inference will be that the marl beds, which, 

 in a vertical line, are beneath a mass of sand, are before them in re- 

 spect of time ; not, as we now imagine, that any one group or portion 

 of a series had priority as a whole. 



The application of these several conditions of accumulation to the 

 deposits which form our tertiary and secondary series of formation, 

 forms the second part of this communication : and the only point I 

 would now notice, connected with the bed of the Channel, is the re- 

 markable irregularity it presents at its western boundary, but which 

 it would have been premature to have noticed in the early observa- 

 tions on the Channel as a physical area. 



The law of progressive change in the character of sea-bed requires that 

 the most remote deposits of the Channel should be the finest, and that 

 no coarse materials should occur at any considerable distance from the 

 coast : this law holds good for a given extent round all the shores of the 

 Channel, but beyond the area of mud and ooze, fine znd. coarse sands, 

 shingle and bare rock are again met with. It will be seen by the 

 map that the Channel bed slopes gradually west through 8° or 9° of 

 longitude, but that instead of running on with such inclination into 

 the valley of the Atlantic, after having attained a depth of 90 and 

 100 fathoms, it rises again to within 50 and 60 fathoms of the sur- 

 face : it is on the sides of this rise that the coarse beds occur. The 

 moving power of the sea at 60 fathoms (the highest level of these 

 rises) is limited to fine sand ; but the v/hole of these groups, whether 

 the Sole Banks or Jones's, are separated from the zones of coarse ma- 

 terials depending on the coast-line, hj a broad intervening area of the 

 finest quality of sea-bed. We are precluded from supposing that the 

 lines of coarse materials can have travelled over the mud zones, as 

 their upper surface is soft and incoherent, into which the sounding- 

 lead sinks some distance before the mass is tenacious enough to stop 

 it, and in which the dredge buries : if therefore marginal or sub- 

 marginal zone materials are found in places beyond well-defined areas 

 of the low moving power of water, they become a clear indication that 

 since their accumulation a great change in the position of such place, 

 as to depth of water and distance from coast-line, has taken place. 



If we take the contour-lines of the Channel valley as they are given 

 on the accompanying map, beginning from the coast, it is very evi- 

 dent that they conform to the features of that coast-line, particularly 

 where it is due to physical structure ; a larger scale, and an interme- 

 diate 5 -fathom line would show this in a very remarkable manner, in 

 the case of one or two valleys of fracture : the features derived from the 

 direction of given masses are continued through the submerged portion 

 of the valley, and are merely modified by the quantity of modern sea- 

 bed accumulated over them. Thus the Channel Islands are the west 



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