After a continuance of the wind in one quarter for a few days--south or south-west--the opposite shores are lined with such weeds carried across, together with great quantities of dead branches fallen from the trees and willows. So that on a small scale the same thing happens as with the drift wood of the ocean; and, indeed, by studying the action of natural forces as exhibited in our own pools and brooks, it becomes much easier to comprehend the gigantic operations by which the surface of the earth is altered. For instance, the north-eastern edge of the water is continually encroaching on the land, eating away the sandy soil, showing that the prevalent winds are south and west. The waves, thrown against the shore with the force they have acquired in rolling six or seven hundred yards, wash away the earth and undermine the bank, forming a miniature cliff or precipice, the face of which is always concave, projecting a little at the foot and also at the top. So much is this the case that an unwary person walking too near the edge may feel the sward suddenly yield and find it necessary to scramble off before a few hundredweights of earth subside into the water. In this process the loamy part of the earth is dissipated, or rather held in suspension, while the small stones and ultimately the heavier sand fall to the bottom and form the sandy floor preferred by the fish. The loam discolours the water during a storm for several yards out to sea, so to say; so that in a boat passing by you know by the hue of the waves when you are approaching the dangers of the cliffs. This continuous eating away of the earth proceeds so fast that an old hollow oak tree now stands--at what may be called the high tide of summer--so far from the strand that a boat may pass between. Like a wooden island the old oak rears itself up in the midst; the waves break against it, and when there is but a ripple the sunlight glancing on the water is reflected back, and plays upon the rugged trunk, illuminating it with a moving design as the wavelets roll in. The water is so shallow at the edge that the shadows of the ridges of the waves follow each other over the sandy floor. They reflect the bright rays upon the tree trunk, where they weave a beautiful lacelike pattern-- beneath, their own shadows glide along the sand. That sand, too, is arranged by the ripple in slightly curved lines. These wave-marks, though so slight that with the hand you may level fifty at a sweep, have yet sometimes proved durable enough to tell the student after many centuries where water once has been. Under the foundations of some of the oldest churches--the monks loved to build near water--the wave-mark has been found on the original soil. In a hollow of the old oak starlings have made their nest and reared their young in safety for several seasons. They seem to understand that the water gives them protection, for their nest would not be out of reach were the tree on land.