converted a tract of land of some 2000 square miles area, into an inland sea. To the north-west of the subsided district, and running in a parallel direction with it, one of the level plains about this region, some fifty miles in length from east to west, and about sixteen miles wide from north to south, was uniformly raised ten feet above the level of the delta.
We will now dismiss this part of the subject with a mere passing allusion to the well known changes of level of the celebrated temple of Puzzuoli, near Naples; the rising and sinking of the land in Scandinavia; and submarine forests on the shores of England, France, North America, &c.; and will conclude this chapter with a few brief remarks about submarine volcanoes and extinct volcanoes.
The subterranean fires, the source and cause of volcanic eruptions and earthquakes, act also on the beds which form the bottom of the sea. When the vents formed by volcanic action lie beneath the waters of the ocean, they are called "submarine volcanoes." The existence and action of submarine volcanoes, long suspected and conjectured, has since the beginning of this century been clearly proved, by the formation of new islands above the waters of the ocean.
The first well-ascertained instance of the elevation of a new island by a submarine eruption, occurred in 1811, near St. Michael, in the Azores. Various eruptions had at different times taken
