In an admirable review of the subject written by Charles M. Skinner we are presented with a picturesque outline of the glacial theory. We are reminded that Brooklyn stands on rubble that was rolled down from the New England mountains to the northward by a glacier larger than the combined areas of all the glaciers now existing on the earth. How many thousands of years ago this great glacier began its work we may only guess within somewhat liberal margins. This continent of ice covered the whole of the northern part of North America, burying mountains beneath its bulk and hollowing the beds of the great fresh-water seas that Chicago and its sister cities front upon to-day, burying, too, for aught we know, the remains of civilizations, though nothing at present has been taken out of the glacial drift, except rude stone implements, to show what the probable condition of man was at that time. This ice lay so deep that not even Mount Washington barred its advance, and to-day geologists find the summit of this mountain heaped with blocks of stone that were dragged from other points and left there when the ice melted; for glaciers are not stationary, like ice on ponds and marshes, but have an onward movement toward their point of melting that varies, with the slope of their beds, from six to thirty-six inches a day. In Greenland the whole interior is covered with ice thousands of feet thick, the movement of which is hindered by a wall of mountains that nearly surrounds that island, but wherever a valley opens a way for it the ice sends down a tongue to the sea, and from these tongues the ocean currents break off the icebergs that float down the Atlantic. In their descent these glaciers act as plows, wearing off so much earth and rock from the hills that the icebergs are freighted with them, and where they melt their stony burdens sink to the bottom of the sea, forming the Grand Banks of Newfoundland.