Page:Cornwall; Cambridge county geographies.djvu/70

 54 CORNWALL As may well be supposed, the action of the sea on the coast-line has been affected largely by the character of the rocks against which the waves have lashed themselves to Perranporth Rocks foam. Where the rocks are of granite or slate, the tide and the waves have very little effect upon the outline of the coast; it is in those places where the softer rocks