So runs, as far as it is possible to reconstruct it in general terms, the geological history of Cape Cod. The east and west arm of the peninsula is a buried area of the ancient plain, the forearm, the glaciated fragment of a coast. The peninsula stands farther out to sea than any other portion of the Atlantic coast of the United States; it is the outermost of outer shores. Thundering in against the cliff, the ocean here encounters the last defiant bulwark of two worlds. II The cliff I write of and the bordering beach face the Atlantic on the forearm of the Cape. This outer earth is now scarce more than a great dyke or wall some twenty-five miles long and only three and four miles wide. At Provincetown it rises from the sea, beginning there in a desert of dunes and sand plains of the ocean’s making. These sands curve inland toward the continent, bending toward Plymouth even as a hand may be bent down at the wrist, and Provincetown harbour lies in the curve of palm and fingers. At Truro, the wrist of the Cape--the forearm simile being both exact and inescapable--the land curve falls from the east and west down through an arc to the north and south, and the earth cliff begins and rises rather suddenly to its greatest elevation. South by east from the Highland Light to Eastham and Nauset Coast Guard Station, the rampart fronts the sea, its sky line being now a progress of long undulations, now a level as military as a battlement, hollows and mounded hills here and there revealing the barren moorland character of the country just above. At Nauset, the cliff ends, the sea invades the narrowing land, and one enters the kingdom of the dunes. [Illustration: _The Beach_] The cliff ends, and a wall of ocean dunes carries on the beach. Five miles long, this wall ends at a channel over whose entrance shoals the ocean sweeps daily into a great inlet or lagoon back of the dunes, an inlet spaced with the floors of tidal islands and traced with winding creeks--the inlet of Eastham and Orleans. Very high tides, covering the islands, sometimes turn this space into bay. Westward over the channels and the marshland one looks to the uplands of the Cape, here scarce a good two miles wide. At Eastham, the land is an open, rolling moor. West over this lies Cape Cod Bay. A powerful tribe of Indians, the Nausets, once inhabited this earth between the seas. Outermost cliff and solitary dune, the plain of ocean and the far, bright rims of the world, meadow land and marsh and ancient moor: this is Eastham; this the outer Cape. Sun and moon rise here from the sea, the arched sky has an ocean vastness, the clouds are now of ocean, now of earth. Having known and loved this land for many years, it came about that I found myself free to visit there, and so I built myself a house upon the beach.