KING GLA.CTAL AKD 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 
kShacklewell Lane, AVest iiackney, which " a fiords 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 by 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 otf 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. Eamsay 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 l^rixham, Gower, and AVookey-hole 
districts. Prestwich has 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 — AVhat gave rise 
to the glaciers which scooped out the " Biddenham flint-implement 
gravel," and eff'ected the other erosions above alluded to ? AVere 
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 glaciation 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 llo-fathonis terrace of the Irish submarine plateau 
became elevated aboA e the sea. Considering, however, the diminished 
* Joui'a. Gcol. Soc. vol. xi. p. 110. 
