The island of Acroteri, famous in ancient history, is represented to have risen from the sea, in a violent earthquake; its surface is composed of pumice-stone incrusted with a covering of fertile earth. Four neighboring islands have been attributed to a similar cause, and yet the sea about them cannot be fathomed by any sounding line. These have risen at different periods, the last in 1573, the first long before the birth of Christ. Similar eruptions of islands have occurred in the group of the Azores. Thus in December, 1720, a violent shock of an earthquake was felt at Tercera. During the night, the top of a new island appeared, which ejected a huge column of smoke. The pilot of a ship who attempted to approach it sounded on one side of the new formed island, but could not reach bottom with a line of sixty fathoms. On the opposite side, the sea was deeply tinged with various colors, white, blue and green, and was very shallow. This island gradually diminished in size, and finally altogether disappeared. History abounds with accounts of floating islands, but they are either false or much exaggerated. These islands are generally found in lakes, and are composed of the light matter floating on the surface of the water in cakes, forming, with the roots of plants, collections of different sizes, which, not being fixed in any part to the shore, are driven about by the winds. In the course of time, some of them arrive at considerable size. The floating islands, however, mentioned by the old writers, have now disappeared or become fixed. CHAPTER X.――CAPES AND PENINSULAS. _Cape Ann_, the northern limit of Massachusetts Bay, is a rocky promontory, fifteen miles in length, containing several good harbors. The peninsula of _Cape Cod_, in the south-east part of Massachusetts, is about sixty-five miles long, and from one to twenty miles broad; its shape is nearly that of a man’s arm bent inward at the elbow and wrist. The greater part of the peninsula is a barren desert; in the south-western portion the land, though sterile, is under some little cultivation; but the northern part consists almost wholly of hills of white sand. The houses are built upon stakes driven into the ground, with open spaces between for the sand to drift through. The cape is well inhabited, notwithstanding its sterility, and supports a population of twenty-eight thousand, who derive their subsistence chiefly from the fisheries. The coast is beset with numerous shoals, and has long been the dread of mariners. At the first settlement of the country, there was an island east of the cape, about nine miles out at sea, which was twenty acres in extent, and covered with savin and cedar trees; for a century this island has been entirely submerged, and the water is above six fathoms deep.