Most of the important rivers of Europe start as streams of ice-water, flowing out of glaciers. Notice the boulders along the side of the stream. They also came out of the body of the glacier, where, as we shall see when we take up "The Stones of the Field" in Chapter VII, the boulders that rode south with the glaciers got most of their roundness. ] We know already what a hand the glaciers had in the Ice Age in shaping the course and conduct of rivers, and you may be sure they have something to do with the making of rivers to-day. The under side of a glacier gets warmed from three sources: (1) its own pressure; (2) the friction as it moves; and (3) the heat from the inside of the earth which, on account of this thick ice blanket, can't get away into the air as it does elsewhere. This heat melts the ice and, as we know, there is water melting also on the surface of glaciers and in the crevasses. Beside all this the water of rains falls upon the glacier so that there is plenty of water to make rivers, and we always find streams of water running from a glacier's front. Most of the rivers of Central Europe start in this way. THE BEAUTY OF THE BRIDAL VEIL And, although they didn't make the rivers themselves, the Ice Age Glaciers are held responsible for the fact that many little rivers always have to jump to catch the train. That is to say, they come tumbling over falls to join the larger streams into which they empty. The reason of this is that when, in the Ice Age, the glaciers filled the river valleys the larger glaciers in a main valley dug below the tributary valleys and so left the mouths of the tributary rivers high up on the main valley's walls. The famous "Bridal Veil" in the Yosemite is one of these side valley falls. The fall--900 feet--is so great that the water widens to a fleecy foam and waves back and forth in the wind like a gauzy veil and, instead of a roar like Niagara, it makes a rustling sound like silk. While some rivers come hurrying down like that--as if they really were afraid the larger river would go off and leave them--others, like the Amazon, roll on as stately as a Lord Mayor's procession. But the waters of all are on their way to the sea. The rock layers, owing to the wrinkling of the earth as it shrinks, are nowhere level, so flowing water is always on a down grade, sloping toward the sea or toward other land that does slope toward the sea. Then remember too as the sea bottom keeps sinking the continents keep rising, which increases the pitch of the land. [Illustration: JUMPING TO CATCH THE TRAIN See the famous Bridal Veil Falls in the Yosemite Valley hurrying down to reach the river below. As the stream descends, it broadens into a beautiful, filmy veil. ] All very simple, but none the less grand and impressive. Ruskin, in one of the noblest of his passages, says: