THE LITTLE MOUNTAIN IN THE BIG CITY In one of the parks in New York City you can see this illustration of how the glaciers rounded off the mountain-tops.] [Illustration: THE BEEHIVE MOUNTAIN This huge mass in the Canadian Rockies is known as the Beehive Mountain. Originally a cliff, it was reshaped by the glaciers. Can't you tell from the picture which was the face of the cliff, and from the information in the text which side the glacier climbed up and on which side it tobogganed down?] There were three great centres--union stations, we might call them--from which the ice trains moved out. These were the points at which the ice gathered to the greatest depth, the tops of the great snow banks. One, as you see by our Ice Age map, was away over on the Pacific Coast of Canada. It is called the Cordilleran Centre, from the vast mountain system of which it is a part. Over what is now the province of Keewatin, Canada, was the Keewatin Centre, while the Labrador Centre stood guard over the highlands of Labrador. The ice from the Keewatin and Labrador fields, you notice, flowed farthest to the south. The Keewatin ice giant travelled away down the Mississippi Valley as far as the mouth of what is now the Missouri, while the giant from Labrador got nearly to the mouth of the Ohio. [Illustration: THE OLD MEN OF THE MOUNTAIN AT THEIR WORK Don't you always think of a glacier as a big white thing? So it is when it starts to work, but after it has ploughed down the mountain valleys and gathered up a lot of soil--such as the heaps you see in the foreground of the picture--it begins to look as black as a coal-heaver! It gets cracked up into all sorts of odd shapes, too. Doesn't that figure near the centre look like some queer kind of old elephant, with a fierce white eye (it's a big stone) and a snarl on his face?] The reason Old Mr. Labrador didn't reach the mouth of the Ohio--as you can easily guess--was that he didn't go far enough, but could you answer a conundrum like this: "Why was Mr. Keewatin bound to reach the mouth of the Missouri and stay there for awhile no matter how far he went?" The answer is easy, when you know it. Because he made the Missouri himself. What we now know as the Missouri River was made of other rivers that the big ice sheet turned around as it advanced and of the water from the ice as the glacier melted its way back home. It was something like Mary and the little lamb, all the time, so long as Mr. Keewatin travelled south; for everywhere he went the Missouri was _sure_ to go, because he kept pushing it ahead of him. HOW THE OLD MEN PUSHED THE MISSISSIPPI ABOUT As the ice sheets pushed into its valleys, now from the northeast and now from the northwest, the Mississippi River was pushed back and forth as if it were a--well, as if it weren't anything! It is known that the Mississippi was pushed out of bed by this burly guest from the north because its former channels have been traced along the old ice fronts.