THE COAST 55 prevail, and where exposure to the prevalent wind induces breakers of great volume, that the loss of land by the action of the sea is greatest. In fact, the tides rarely run beyond one or two miles per hour, except round headlands, and it is where the rocks are of a yielding character that the coves and bays are formed. This is not always the case. Where the sea has found a fault in the rock it will burrow incessantly till it has bored out for itself a cavern, and the head of this falling in produces a tiny cove. The hard quartzose and trap rocks of Trevose Head, the greenstone rocks of Pentire, near Padstow, the hard slates of St Agnes, the greenstone and hardened schist of the Gurnard's Head, and the granite of the Land's End, defy the action of wave and tide. But it is otherwise where, for instance, the Head of Rubble occurs. "In Gerrans Bay it is plain that the cliffs of Head were at one time much further out than they are now. The tops of the earthy cliffs are split with cracks and miniature chasms, showing that great masses are constantly being detached by atmospheric causes, while the great heaps of earth at the foot of the cliffs show how for centuries masses of earth have rolled down from their tops on to the beach below 1 ." As to the kingdom of Lyonesse, which was sup- posed to extend from the Land's End to beyond Scilly, it never existed in the historic or prehistoric period. Another fable that may be dismissed, is that St Michael's Mount was surrounded by a vast tract of woodland, in which were villages, and where settled hermits. It did rise 1 D. C. Whitley, "The Head of Rubble," in Journal of the R. Inst. of Cornwall, xvn. p. 67.
