12 PROCEEDINGS OF THE GEOLOGICAL SOCIEir. [NoV. 9, 



prior to tlie excavation of the Weald valley, whether of Lower 

 Tertiary age or of some subsequent period) which occur near to, 

 and even on, the chalk escarpment, and are shown in the accom- 

 panying map. These, however, clearly could not have supplied the 

 pebbles to the Kennington, Willesboro', and Smeeth gravels, which 

 lie within a separate drainage-area — that of the Stour ; and if we 

 suppose those gravels that are shown in the map as lying within the 

 area of the Medway drainage and containing Tertiary pebbles to have 

 been supplied from this source (straining our imagination, and ig- 

 noring, in order to do so, various physical features that conflict with 

 such a direction of supply), we ought for consistency to find Tertiary 

 pebbles in increasing proportions in those gravels of the Medway 

 drainage-area, both higher and lower, which lie nearer and nearer 

 to these scarp beds ; but such is not the case. 



"While the introduction of these pebbles, and the nature and form 

 of the area of denudation seem to me alike repugnant to any con- 

 ceivable river-agency acting in the direction of the present streams, 

 the position and mode of occurrence of aU the gravels within this 

 part of the Weald appear to me to be just what might be expected 

 from the sequence of events after the Thames gravel which I have 

 in previous papers put forward ; and this sequence I wiU endeavour 

 here to trace in harmony with the composition and position of such 

 gravels. 



I should premise, in order to remove misapprehension, that I have 

 never entertained, and wholly reject, the hypothesis of the escarp- 

 ments having ever been cliffs, although they appear to me to have 

 formed sea-margins and steep foreshores*. The absence, however, 

 of beds with contemporaneous marine fossils within the Weald, either 

 at the feet of the escarpments or on elevations within the major 

 valley, does not seem to me to be entitled to any weight ; for there 

 is proof, from the envelopment of some two or three miles of it in 

 Boulder-clay, that the escarpment of the Yorkshire Wold existed 

 during the glacial period, and must therefore have been a sea-mar- 

 gin, because, in whatever way this Boulder-clay was formed, no one 

 can deny that the Yorkshire Wold passed under the Glacial sea ; and 

 if the valley below it was filled with, and the Wold covered by, ice 

 when subsiding, they were clear of this when emerging, and under- 

 went great denudation during that process. The features exhibited 

 by sections of mine, ISTos. 7 & 8, at p. 402 of the 23rd volume of the 

 Society's Journal, render it difficult to deny that the same thing oc- 

 curred with respect to the chalk-escarpment of Herts and the lower 

 grounds below it. Nevertheless we do not in either of these cases 

 meet with beds with marine fossils referable to this period of emer- 



* While rejecting the hypothesis of scarps being in any way allied to cliffs, I 

 cannot admit that the absence of beaches at their feet is any argument in the 

 case, because hundreds of steep acclivities in the north of England and in Scot- 

 land that could not have been any thing else than cliffs when emerging from the 

 glacial sea, are quite destitute of beaches at their feet. Some of these, such as 

 Grristhorpe cliff in Yorkshire, shown by me and Mr. Eome in section at p. 180 

 of the 24th volume of the Quarterly Journal, have now become cliffs again, and 

 have the beach at their feet, which they had not when rising out of the glacial 

 sea. 



