Geological Society of London. 99 - 
marine deposits with recent shells at the height of from three hun- — 
dred to five hundred feet above the sea. 
It is natural to inquire what changes the surface of the dry land 
in England may have undergone during the occurrence of such up- 
ward and downward movements. Perhaps some observations lately 
made by Mr. Bowerbank in the south of the Isle of Wight may elu- 
cidate this point. He bas given us an account of a bed of chalky 
detritus, containing recent land shells, at Gore Cliff. This bed is 
ten feet thick, and rests immediately upon chalk marl. Many of the 
shells, which are plentifully scattered through it, retain their color. 
As the deposit ranges to the foot of St. Catherine’s Down, it is pos- 
sible that the waste and denudation of that chalk hill: may have sup- 
plied the materials. I have lateiy seen similar detritus resting on 
the chalk with flints, and arranged in numerous thin layers in the 
section exposed in cutting the railroad at Winchester, where a black . 
layer of peaty earth and carbonized wood intersects thin layers of 
white chalk rubble, from twenty to thirty feet thick. Such appear- 
ances are, in fact, very general in chalk districts; a bed of flints not 
water-worn occurring on the highest downs, while fragmentary chalk, 
often inclosing land shells, occurs on their slopes and at lower levels. 
Violent rains have been known even of late years to tear off the turfy 
covering from certain points near Lewes, and to wash away flints 
and chalky mud, and leave them in the hollow combs or flanks of 
the hills. This action of the elements would be most powerful at 
periods when the chalk first emerged from the sea, or whenever ‘it 
assumed in the course of subterranean disturbances a new position or 
physical outline. 
We must, I think, infer from the occurrence of certain recent ma- 
rine shells and shingles in the bottom of what has been termed the 
elephant-bed at Brighton, that, the chalk in the Southeast of Eng- 
land has undergone some movements of a modern date, the land - 
having subsided there to the depth of fifty or sixty feet, and having 
been subsequently raised up again to a level sms higher than 
its original position.* 
If it should appear upon careful research that that the land shells 
found in terrestrial alluviums covering the chalk are almost universally 
of recent species, I should not conclude that the emergence of the 
chalk hills from the sea had generally occurred at a very modern pe- 
* See Principles of Geology, 4th edit., vol. iv. p. 274. 
