The bars along the coast shift with every storm, and in many places there is occasionally none at all. We ourselves observed the effect of a single storm with a high tide in the night, in July, 1855. It moved the sand on the beach opposite the light-house to the depth of six feet, and three rods in width as far as we could see north and south, and carried it bodily off no one knows exactly where, laying bare in one place a large rock five feet high which was invisible before, and narrowing the beach to that extent. There is usually, as I have said, no bathing on the back-side of the Cape, on account of the undertow, but when we were there last, the sea had, three months before, cast up a bar near this lighthouse, two miles long and ten rods wide, over which the tide did not flow, leaving a narrow cove, then a quarter of a mile long, between it and the shore, which afforded excellent bathing. This cove had from time to time been closed up as the bar travelled northward, in one instance imprisoning four or five hundred whiting and cod, which died there, and the water as often turned fresh, and finally gave place to sand. This bar, the inhabitants assured us, might be wholly removed, and the water six feet deep there in two or three days. The light-house keeper said that when the wind blowed strong on to the shore, the waves ate fast into the bank, but when it blowed off they took no sand away; for in the former case the wind heaped up the surface of the water next to the beach, and to preserve its equilibrium a strong undertow immediately set back again into the sea which carried with it the sand and whatever else was in the way, and left the beach hard to walk on; but in the latter case the undertow set on and carried the sand with it, so that it was particularly difficult for shipwrecked men to get to land when the wind blowed on to the shore, but easier when it blowed off. This undertow, meeting the next surface wave on the bar which itself has made, forms part of the dam over which the latter breaks, as over an upright wall. The sea thus plays with the land holding a sand-bar in its mouth awhile before it swallows it, as a cat plays with a mouse; but the fatal gripe is sure to come at last. The sea sends its rapacious east wind to rob the land, but before the former has got far with its prey, the land sends its honest west wind to recover some of its own. But, according to Lieutenant Davis, the forms, extent, and distribution of sand-bars and banks are principally determined, not by winds and waves but by tides.