with the water and goes along with it. Stones are loosened and rolled along, too. Fill a big gold-fish bowl with this muddy water at- the mouth of the brook, and let it stand awhile to settle.
Through the glass you see clear water at the top, then mud, then sand, then gravel. The gravel falls the lowest because it is the heaviest. The little brooks rob the hill sides of the soil that plants need, as well as of the water. They melt and break up and this soil as fine as they can. They even take some sharp corners from the pebbles by rolling them over and over in the water. Running water is a busy miller. It grinds earth to mud, and rocks to sand. Then, when it gets down to low ground, where it flows more slowly, it drops all this heavy matter along the river banks, in the river bed, and far out into the ocean. The gravel drops first, then the sand, then the mud. If you dig a well in the valley you will find a layer of loam on top, then sand, then gravel, on a bed of stiff clay or rock. If you scoop out a river bed you find things in the same order. In the ocean you find the gravel near the shore. It hurts your bare feet when you go in bathing. The sand is farther out, and the mud farthest of all. The water sorts all this earthy matter and puts each kind by itself. Isn't that wonderful? The top layer of loam is a mixture of clay and sand and leaf mold. Leaf mold is added every season by falling leaves and decaying seeds and roots. It makes the soil softer and richer.
This water miller has several stout helpers in wearing down land. One is wind. Wind picks up dust and scatters it. Then it is more easily washed into the streams by rain. Frost is a regular little wedge and hammer. When water freezes in a crack in a rock it swells, or expands, and splits the rock into pieces. The roots of all plants and trees split the soil, too.
