Sand dunes, as distinct from sandspits, or the banks at the head of the beach, are found in a few restricted areas on the Cape, but their two primary locations are the Provincetown hook and at Sandy Neck in Barnstable, on the Bay side. Inland of the beach, far enough not to be exposed to the constant wash of the tides or to flooding seas during storms, the dunes have forms and motions of their own. They were originally produced by the wind, and it is the wind that reshapes them, blows over their shoulders and down their slopes, making mounds and ripples on their surfaces, and also undoes them and makes new ones again. The Provincetown dunes, which I had passed by on my June hike down the beach, represent an exposed region of several miles in extent, uninhabited for the most part except for a few gray beach houses perched on the dunes overlooking the sea. They are continually being added to by sand which the dry northwest wind picks up along the shore and blows inland. Because of its dryness, this wind also has the greatest effect in moving the dunes. Damper winds causing moisture on grains of sand, make them more resistant to being moved. Much of the region is held down by low vegetation. Its sandy reaches are patched everywhere by Hudsonia, or beach heather, pitch pines kept down almost flat on the ground by wind and salt spray, and its slopes and hummocks kept intact by beach grass; but in other areas, and they are extensive, the dunes have broken loose and roam like the waves of the open ocean, with great crests and long, deep troughs. They look as if they should have a slow, massive momentum of their own, but they are moved by the wind, migrating in a west to east direction at the rate of some ten to fifteen feet a year, creating a considerable problem at the point where they skirt the highway across from the town of Provincetown. On the far end of Pilgrim Lake high dunes loom over the highway and are continually drifting down on to it, hardly deterred by snow fences and the planting of beach grass, so that the sand has to be cleared off frequently. [Illustration] It is a young country, even compared with the rest of the Cape, which, in geologic terms at least, is by no means an ancient land. It is postglacial and is made of material brought along the shore and added to a reef of glacial debris. It begins where the glacial material of the lower Cape ends, easily seen where the cliff at “High Head” breaks off above Pilgrim Lake, and then it stretches and curves out very close to sea level. Samples of material taken in the area showed a carbon dating of 5000 years, comparatively recent times. Also there seems to be good reason for believing that much of the dune country was broken free and set to wandering by the hand of man.