Mountains are also formed where the molten rock on the inside of the earth is forced up under layers of rock nearer the surface. This lifts these rock layers into domes. In the course of time the rivers and the weather wear away the overlying rocks, leaving the hard central core standing out. Harder layers of the overlying rock, wearing down less rapidly than the other layers, often stand out as circular ridges with valleys in between, so that the central core looks like some old ring master at a circus. The Bear Paw Mountains and the Little Snowies of Montana are mountains of this type. WHERE MOUNTAINS GET THEIR PEAKS Most mountain peaks, except those of the volcanoes, are remnants of hard rock which have been left standing while the rivers and the weather cut away the softer rock around them. [Illustration: IN THE HIMALAYAS THEY MIGHT CALL THESE "HILLS" High as these mountains are--we are right on the roof of the Rockies--if they were in the Himalayas they might be called "hills," because there the scenery grows so much taller. What does the sharpness of the peaks say as to the age of these mountains? Compared with the Appalachians, for example?] In regions of gently rolling country even small hummocks are sometimes called "mountains," while out West, where scenery grows so tall, the Black Hills seem to the people only stepping-stones to the big Rockies. So they call them "hills." In the region of the Himalaya Mountains--mountains that don't think anything, you remember, of climbing up 16,000 to 30,000 feet in the air--a peak of 10,000 feet is often called a "hill." II. Hills That Were Moved In Nearly every region has hills, because every region has or has had running streams and the streams have carved out the hills. But there are kinds of hills that aren't home-made; they were made elsewhere and moved in. I believe this is the biggest hill secret of all, speaking of hills proper and not of mountains. [Illustration: _From Norton's "Elements of Geology." By permission of Ginn and Company_ KAME SCENERY IN NEW YORK STATE] Almost all over the northern part of North America, as well as much of Europe and Asia, there are mounds, heaps, and hills of various shapes and sizes made up of a mixture of pebbles, sand, and clay. In the United States these heaps make a big line of hills, like a procession of ancient Indian chiefs, with bowed heads and stooped shoulders, plodding back to the land of their fathers. And, sure enough, there they go from down East clear across country to the far West and then up North, where, as we know, these hill-moving giants, the glaciers, came from.[19] For, beginning with Perth Amboy, N. J., say, you will find them marching on through Elmira, N. Y., skirting the suburbs of Cincinnati, winding their way through Indiana and Iowa up through Wisconsin to the Dakotas and Montana, and so back into Canada.