BEACH ON PLYMOUTH HOE. 
115 
of the ancient beach on Plymouth Hoe (now nearly 
destroyed) is about 30 feet above present high 
water mark. The rock on which it rests is often 
smoothened, and specimens of pholas dactylus are 
slope of beach, (as some may think, though I incline to think not) 
or to the graduated mode of elevation , so especially indicated in 
that one spot just particularized. 
With regard to the accurate assortment of the pebbles consti¬ 
tuting the various laminae of this ancient beach, it appears to he 
occasioned by the different power which the sea employs at the 
times of its agitation, since, the degree of force which it has will 
occasion a difference in the size of the bodies which it throws 
up,—when the momentum is considerable, the rush of fluid dis¬ 
dains the smaller substances, but selects those presenting more 
■ onsiderable surfaces, and vice versa. Where extensive areas of 
beach occur, this fact is apparent in the different sizes of the 
pebbles found assorted as it were over its whole extent. Near 
Portland in Dorset is a beach of this kind, and so regularly are 
the pebbles disposed over it, that at night, fishermen or those 
frequenting it, by merely examining with the hand the size of 
the pebbles on which they are standing, can tell with tolerable 
accuracy on what part of this extensive line of shingle they are 
situated. 
. Piece of the ancient beach, shewing the consolidation of its strata 
towards their interiors. 
