On the eastern continent I might quote a multitude of analogous cases. There is, for instance, the Wady el Jeib, in soft limestone, within the Wady Arabah, south of the Dead Sea. The defile is one hundred and fifty feet deep, half a mile wide, and forty miles long. In Mount Lebanon, several remarkable chasms in limestone have been described by American missionaries, as that on Dog River, (Lycus of the ancients,) six miles long, seventy or eighty feet deep, and from one hundred and twenty to one hundred and sixty feet wide; also, Wady Barida, whose walls are six hundred to eight hundred feet high. On the River Ravendoor, in Kurdistan, is a gorge, described in a letter from Dr. Perkins, one thousand feet deep. Another on the Euphrates, near Diadeen, is seventy feet deep, and is spanned by a natural bridge one hundred feet long. On the River Terek, in the Dariel Caucasus, is a pass one hundred and twenty miles long, whose walls rise from one thousand to three thousand feet high. In Africa, the River Zaire has cut a passage, forty miles long, through mica slate, quartz, and syenite; and in New South Wales, Cox River passes through a gorge twenty-two hundred yards wide and eight hundred feet high. Ninthly. Since the geological period now passing commenced, called the _alluvial_, or pleistocene period, certain changes have been going on, which indicate a very great antiquity to the drift period, which was the commencement of the alluvial period, and has been considered among the most recent of geological events. I refer to the formation of deltas and of terraces. Of the deltas I will mention but a single example, to which, however, many others correspond. The Mississippi carries down to its mouth 28,188,803,892 cubic feet of sediment yearly, which it deposits; or one cubic mile in five years and eighty-one days. Now, as the whole delta contains twenty-seven hundred and twenty cubic miles, it must have required fourteen thousand two hundred and four years to form it in this manner. Terraces occur along some of the rivers of our country from four hundred to five hundred feet above their present beds, and around our lakes to the height of nearly one thousand feet. They are composed of gravel, sand, clay, and loam, that have been comminuted, and sorted, and deposited, by water chiefly. At a height two or three times greater, on the same rivers and lakes, we find what seem to be ancient sea beaches, of the same materials, deposited earlier, and less comminuted. The same facts also occur in Europe, and probably in Asia.