Once more, to go back to our glaciers, we find that they tear from the rocks large masses or lumps of stone; and these fragments being ground and dragged in the ice-bed, lose the sharpness of their edges and become rounded and smooth. The icebergs, as they break from the glacier, carry away these stones frozen to their lower surface, and as the ice melts the stones are let fall. These peculiar stones are called boulders, and some name them “lost stones,” as they are found so far away from their original rocks. These boulders, or lost stones, are scattered over a large portion of the Northern hemisphere. On high hills,[31] in wide fields, and deep valleys, they lie as the ice left them. Some are lodged in the most singular places. When we see a boulder on the crest of some high hill it may be hard to believe that once an icy sea rolled over such an eminence and covered it so deep that icebergs with their enormous masses had rocked above it in the cold, dark waves; but so it truly was. Sometimes we see a wide field covered with boulders lying so closely together that very little vegetation can grow among them. In this field, long ago, some iceberg grounded in the shallow waters and, melting away there, left its load of stones. There are some geologists who consider that a solid cap or sheet of ice covered nearly the whole of the Northern hemisphere at some distant time, and that the boulders and boulder-clay were the deposit of this ice-sheet, and were not dropped by floating bergs. It is very likely that there were not only floating bergs carrying boulders, but also an ice-sheet extending below the Polar circle. Altogether the drift, the moraines, the ice-scratched rocks, and the boulders lying solitary hundreds of miles from the rocks of which they once formed a part, point out clearly to us what were the general features of the Glacial age of the world. FOOTNOTES: [30] The bottom of an ice-stream moves more slowly than the surface: this is the case with any stream; thus the surface projects at last beyond the bottom and breaks off in bergs; while at last the lower part enters the valley something like the share of a plow. [31] On the bluffs of the Missouri River, Howard County, Mo., are ice markings, and a lump of copper weighing 23-1/2 pounds was found on these bluffs. This copper was a “lost” lump brought by ice from the coast of Lake Superior.--J. B. S. LESSON XVI. THE FIRST CRUSTACEANS. “Look on this beautiful world, and read the truth In her fair page: see every season brings New change to her of everlasting youth; Still the green soil with joyous living things Swarms, the wide air is full of joyous wings, And myriads still, as happy, in the sleep Of ocean’s azure gulf, and where he flings The restless surge.” --BRYANT.