Parr IL. Szcr. ii. § 6.] MARINE EROSION. 431 
If such is the progress of waste where the materials consist of 
the most solid rocks, we may expect to meet with still more im- 
pressive proofs of decay where the coast-line can oppose only soft 
sand or clay to the march of the breakers. Again, the geological 



































































































































































































































































































































Fic. 162.—BovuLDER OF BASALT PROTECTING THE PoRTION OF BEACH UNDERNEATH 
IT; Larco, Fre. 
- student in Britain can examine for himself many illustrations of this 
kind of destruction around the shores of these islands. Within the 
last few hundred years entire parishes with their towns and villages 
have been washed away, and the tide now ebbs and flows over districts 
which in old times were cultivated fields and cheerful hamlets. The 
coast of Yorkshire between Flamborough Head and the mouth of 
the Humber, and also that between the Wash and the mouth of the 
Thames, suffer at a specially rapid rate, for the cliffs in these parts 
consist in great measure of soft clay. In some places this loss is said 
to amount to 3 feet per annum. | 
While investigating the progress of waste along a coast-line, the 
geologist has to consider the varying powers of resistance possessed 
by rocks, and the extent to which the action of the waves is assisted 
by that of the subaerial agents. Rocks of little tenacity and readily 
susceptible of disintegration, obviously present least resistance to the 
advance of the waves. A clay, for example, is readily eaten away. 
If, however, it should contain numerous hard nodules or imbedded 
boulders, these, as they drop out, may accumulate in front beneath 
the cliff, and serve as a partial breakwater against the waves 
(Fig. 163). On the other hand, a hard band or boss of rock may 
withstand the destruction which overtakes the softer or more jointed 
surrounding portions, and may consequently be left projecting into 
the sea, as a line of headland or promontory, or rising as an isolated 
stack (Fig. 161). But besides mere hardness or softness, the 
