KINO — GLA.CTAL AND POST-GLACIAL DEPOSITS. 



173 



posing that they were produced in the Pliocene period, inasmuch as 

 they could not have escaped being planed down and obliterated in 

 the first epoch of the Glacial period. The glaciers of this last period, 

 I am led to believe, have mainly contributed in giving the Clare 

 Hills, before they became terraced, their leading contours. It does 

 not appear that the terraces, considering their well-defined edges, 

 were affected to any extent by the glaciation of the epoch next to be 

 noticed, except perhaps in the valleys (which run down the slopes), 

 where they are only faintly exhibited.* 



Some of the freshwater deposits which I have placed in the opening 

 stage of the next epoch may belong to the closing stage of this 

 epoch. The land was evidently undergoing minor oscillations at 

 the time, as shown by Prestwich, in his description of the section at 

 Shacklewell Lane, West Hackney, which "affords a clear indication 

 of two gravel periods, separated by an interval of dry land."* I 

 see no reason to doubt that the large earth-crust movements, cha- 

 racterizing the " epochs" of the " Glacial period," were ocasionally 

 accompanied b}>" minor oscillations. 



The " Brighton ancient sea-beach" could not have existed earlier 

 than the close of this epoch, otherwise it and its protecting cliff 

 would have been swept off by the powerful glaciation of the previous 

 (subaerial) one. 



Third (subaerial) epoch. — The Clare Hill terraces have evidently 

 been more acted on by ordinary atmospheric agencies than by gla- 

 ciation : it is, therefore, difficult to adopt any other conclusion than 

 that the glaciers of this epoch were smaller than those of the former 

 (subaerial) one. Ramsay has formed the same opinion from other 

 evidences. Still the glaciers of this epoch must have had consider- 

 able power to scour the " old marine drift " out of Cwm-llafar, and 

 to deeply erode the rocks of the Brixham, Gower, and Wookey-hole 

 districts. Prestwich lias shown that much of the " Biddenham flint- 

 implement gravel" has also been removed by glacial agency. All 

 these phenomena appear to me to be geologically contemporaneous, 

 and, of course, subsequent to the formation of the gravel last noticed. 

 This deposit, however, does not seem to have been formed by the 

 agency of ice, although the one may have indirectly contributed to 

 the formation of the other. A question next arises — What gave rise 

 to tht 1 glaciers which scooped out the " Biddenham flint-implement 

 gravel," and effected the other erosions above alluded to? Were 

 they produced by an elevation of the land ? or are they to be attri- 

 buted to some other cause — the land remaining at its old level ? 

 Although unable to adduce any positive evidence in favour of either 

 of the views involved in these questions, I am, nevertheless, inclined 

 to adopt the one which admits that the second glaciatit n arose, 

 in the districts named, and in the British area generally, in con- 

 sequence of a great but gradual elevatory movement, which stopped 

 when the second or 115-fathoms terrace of the Irish submarine plateau 

 became elevated abo\ e the sea. Considering, however, the diminished 

 * Journ. Geol. Soo. vol. \i. p. 1 in. 



