[Illustration: HOW THE MOUNTAIN TORRENTS HELP SHAPE THE BOULDERS] The only thing that could handle boulders in this way, so it turned out, were the glaciers. By following up the boulders to their homes in the mountains they found on the backs of the glaciers of to-day stones just like those in our fields, and they found them thickly scattered over the ground where the glaciers melted back during the summer months. The glaciers not only pick up boulders from the mountain torrent beds, as they move along, but themselves pluck rocks from mountain sides. Huge blocks of rock, dislodged when water freezes in the cracks of the mountain walls, also fall upon the glacier. It was the boulders held underneath the ice that left their autographs, deep grooves on the native bed-rock in the regions into which the glaciers of the Ice Age came. These great ice rivers filled the mountain valleys, and reaching far up on the mountain sides carried boulders to those heights. Sometimes the glacier left the stones standing on a narrow point on top of other rocks--so making the rocking stones. [Illustration: HOW THEY KNOW THE OLD MEN DID IT Here is one of those heaps of boulders, pebbles, and soil that the glaciers of the Ice Age brought and left behind them. They know those ancient glaciers did this, because just such heaps are found under the edges of glaciers to-day. ] III. Leaves from the Family Records of the Boulders What I have said so far of the Boulders is mainly about their travels into foreign lands and how they were received by intellectual people. But there are many other interesting things to be found in their family records that you will want to know about, I am sure. HOW THE BOULDERS RODE ON THE WATER One of these is how they came to ride on the water, when I said just a little while back that only _ice_ could carry them across mountain valleys, and pile them up on the mountain sides. That was all true; yet, under certain circumstances, boulders _have_ ridden on the water. As the glaciers melted away finally in those early days the water, as you know, helped make rivers and lakes. Then, from the front of the glaciers icebergs broke off and floated away down the rivers or across the lakes. In these icebergs boulders were often imbedded, and so were dropped wherever the iceberg carried them before it dissolved. [Illustration: HOW THE BOULDERS RODE ON THE WATER This is a scene in August in Glacier National Park. It illustrates how boulders of the Ice Age travelled by water, when icebergs containing them broke from the glaciers and floated away on rivers and lakes. ]