But where did the bergs come from? That, too, is very curious. Among the mountains in the far north, just as in Switzerland, there are great rivers of ice, called glaciers. They look like rivers frozen clear to the bottom, and the weight of the ice is forever pressing it downward toward the sea, sliding, squeezing, crushing itself into strange forms, and moving a few inches or a few feet or yards per year. Very slow progress, you will say. But then, it is enough. By and by a great mass of it will be shoved so far into the sea that it will break off, a whole mountain of it, and go wallowing away with perhaps twenty cart-loads of sand and gravel and great stones scooped up from the bottom into its crevices, or frozen fast to the ice. By-and-by that berg will drift down as far as Newfoundland, where it will meet the warm water of the Gulf Stream as it hurries northward. The ice will melt, the sand and stones will go silting downward, and by just so much the bottom of the ocean will be a little nearer to the surface. Already there are great banks of such deposits, many miles across, where a ship can anchor, although out of sight of land; and they are great places to go fishing on. More codfish and halibut are caught in such places than anywhere else. Meanwhile the floe was drifting,--the one we started to write about. Right in the heart of it there was a round hole in the ice. A fat brown seal had made it when the ice was not so thick; and he kept it open, so that when the whole ocean was frozen he still could have a place to breathe through. There were other places now, but still he liked to come back home to this one. The snow had blown into the hole and formed a hard crust across it, which kept the colder air out; and after our seal had tired of fishing and felt air-thirsty, he would swim quickly to the place and blow warm breaths against the crust till a little airhole was melted right through it, which was quite enough for him. Just now the seal was not at home. Close to the snow-buried hole lay a great yellowish-white heap, too yellow to be ice, too white to be noticed as different from any other hummock of ice. For hours it had crouched there utterly motionless, save now and then the silent quiver of a small ear hidden in the fur. All day it would stay if need be, patient as death and as sure--the great white polar bear, with claws like hooks of iron, and looked at with respect by Northmen, who gave scant respect to anything else on earth.