The meadow through which we are passing is flat, and covered with wiry grasses which love wet situations. The stuff of which it is made can be seen on the banks of the burn. It is a soft, dark-brown earth, almost without stones, or with here and there a layer of pebbles. How has this meadow been formed? The stream has done it. To find out how the stream made the meadow we must visit it in winter after several days of heavy rain. Then a sheet of water covers the meadow, making it a shallow lake. The water is very still except near the channel of the burn; it is brown and full of mud. For some days the lake remains, then the water begins to fall. The stream is clearer now, though still dark with mud; good water this for the trout-fisher. A few days more and the lake has vanished; the stream keeps within its banks, though it is still full. Now look at the meadow. It is covered with a very thin film of grayish-brown mud. In spring the grasses will grow quickly, and will be greener than ever. The meadow is a little—ever so little—higher for the new sheet of mud it has acquired. Winter after winter this goes on. The brown earth which forms the meadow is flood mud. Its flat configuration is due to its being laid down in a little temporary lake. Let us follow the stream still farther, and leave the meadow behind. The channel gets steeper, and the water flows along quite merrily, faster than in the level meadow below. The bends in the burn disappear. It is in a hurry here and flows straight; in the flat meadow below it loiters and swings lazily to and fro. The channel is shallow, and there are few pools. The banks are often bare rock, or the stony clay which is produced by the weathering of rock. The stream is washing away the clay; it even attacks the hard rocks. To see how this is done you must come when the burn is swollen with heavy rains. Then you will hear it rolling the stones along. They grind on one another, and thus they get their rounded shape, or are broken up into small fragments. As they are rolled along they wear away the rocks and deepen the bed of the stream. Loose pieces are swept away, soft layers are planed down. Many of the cracks and joints are opened and loosened, ready for fresh attacks during the floods of next winter. This is where the gravel comes from. In the lower part of its course the stream cannot move large stones, but in floodtime the smaller pebbles are carried downwards. The big stones lie in the upper stream; they must be broken smaller before they can be carried away. After rainy weather you will often find that a rapid branch stream has shot a big heap of pebbles into the main stream. When the floods rise above the surface of the meadow they may strew sheets of little stones here and there over the grass.