1 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



elephant-bed, and by the exactly corresponding bed at Sangatte, on 

 the opposite coast. At the succeeding period there must have been 

 a great depression, assuming the Drift to have been of submarine 

 origin, since it is now found at elevations of several hundred feet 

 above the sea-level. And this is in perfect accordance with the de- 

 pression which must have taken place, as we believe, at the same 

 period over a great portion of northern and central Europe. It would 

 appear probable that the central ridge of the district, where the Drift 

 is stated to be entirely wanting, was extant above the ocean, and 

 possibly it might be the only part that was so. On this point the 

 author does not appear, I think, to have been very explicit in the 

 statement of his views. He conceives the transport to have been 

 effected by waves of translation, but at the same time he states that 

 " there can be little doubt in affirming, that neither during the ope- 

 rations which deposited the debris, nor after them, was the Weald 

 valley occupied by the waters of a sea, or its transverse gorges by 

 marine narrows*." Whence then came the transporting waves? 

 The author would appear to have left this question open, and perhaps 

 intentionally. The reasons for the opinion quoted above are, the 

 absence of marine remains, of rounded pebbles, and of ancient beaches. 

 These are important facts. It is essential that we examine carefully 

 the extent of the inferences which they justify. 



The absence of marine organic remains in a particular and limited 

 region cannot be accepted, I conceive, as a conclusive proof of that 

 region not having been submerged beneath the sea. In fact we know 

 how few and limited are the localities, either in Europe or North 

 America, in which the period of the Drift has left us recognizable 

 marine organic remains, though their number and distribution are 

 sufficient to prove beyond doubt the submergence of those regions 

 during that period. The true inference from their absence, and from 

 that of tranquilly stratified sedimentary beds, in a particular district, 

 would seem to be, that during the Drift-period, the quiet process of 

 sedimentary deposition was never allowed to proceed iminterruptedly 

 for a sufficient length of time to admit of an accumulation of such 

 sedimentary beds, too large to be swept away during a succeeding 

 period of disturbance. The author's inference that there could have 

 been no submergence at the period alluded to under a sea of ordinary 

 tranquillity, appears to me valid as against the views which he combats ; 

 but his conclusion from the present argument, that there could be 

 no submergence at all, I conceive to be altogether untenable. 



Again, let us examine the conditions under which we might expect 

 raised sea-beaches to be left, in consequence of the elevation of the 

 land and consequent retreat of the sea-margin. Such old beaches 

 may present themselves as ledges or terraces encircling higher 

 grounds, like the Parallel Roads of Glenroy, or the frequent and 

 extensive terraces of North America ; or as mere beds of rounded 

 shingle. Now let us suppose the elevation of any coast-line to take 

 place instantaneously : the " raised beach" would doubtless be trace- 

 able with almost perfect continuity, by means of both the above cha- 

 * Quart. Journ. Geol. Soc. for February 1852, p. 393. 



