But there is another thing that may have helped to make many great mountains run north and south. Bedtime and sunrise used to come a good deal oftener than they do now, for then the earth turned faster on its axis. It turned fastest of all at the equator, just as it does to-day. So the lands in the equatorial belt were pulled up and the belt enlarged. Then, as the speed of the globe slackened, the enlarged belt began to wrinkle because there was not the same amount of centrifugal or "fly-away-from-the-centre" force to make it stand out. So wrinkles came at right angles to the belt, just as do the waist gathers in a dress. And now about the mystery of the mountains and the sea. When we visit the rock mills of the sea along in October[20] we shall notice, among other things, that the rock is made along the sea border, and that the coarsest sediment settles nearest the land. As a result this part of the deposit is built up faster than that farther off shore, and as it gets heavier and heavier it sinks. The deposits farther away from the shore sink, also, but more slowly because these deposits are not piled up so fast. Now, if you come down on one end of a seesaw what happens to the other end? It goes up, doesn't it? The effect of this sinking of the rocks of the sea upon the rocks of the adjoining land is something like that. The rocks that make the continents extend out under the sea, and the weight of the newly laid stone on the sea margin end not only tips the rock beds up, but, sinking in toward the continental mass, wrinkles it up, as the pages of this book will wrinkle if you push them from the front edge. So you get your mountains along the sea border. And they are in parallel ranges, because the land is crumpled up into several folds, like a table-cloth pushed from one side. [Footnote 20: Chapter X, "The Autumn Winds and the Rock Mills of the Sea."] "But," you say, "how about the Rocky Mountains? And the Carpathian Mountains in Europe, not to mention several others? _They_ are not on the borders of the sea." WHY SOME MOUNTAINS ARE FAR FROM THE SEA