But we have not yet exhausted all that the rocks at the cascade can teach us. By dint of some exertion we climb the cliff and gain the upper edge of the fall. The rocks that form the bed of the stream are now seen to be deeply grooved and worn, every exposed surface having a smoothed blunted aspect. We can mark how the stone has split up along the natural lines of joint, whereby great facility is given to the removing power of the current, and how large irregular angulated blocks become detached and are swept down the stream. In not a few parts, too, we may notice circular holes of greater or less depth, in the bottom of each of which lie perhaps a pebble or two, that with a constant gyratory movement, caused by the eddying water, have eaten their way downwards into the solid rock. When the stream is in flood and comes roaring down the rocky gorge bearing along with it a vast amount of mud, gravel, and stones, one can easily see how the friction of the transported material must wear down the hard bed and sides of the channel, and how this process repeated month after month and year after year, must aid the decomposing forces in scooping out a deep ravine. From the cascade the ascent of the stream becomes steeper and the run of water is consequently more rapid. Soon however we emerge from the woody copse, and find ourselves on a flat alluvial cultivated plain through which the rivulet winds in a tortuous meandering course, bending back upon itself into loops that almost meet and well-nigh form broad flat islets. Strolling along this winding route we can mark the effects of the stream in eating away the soft clay and sand at one part of the bend and piling them up at another. Such loose material can present but little resistance to a stream swollen with rains, and consequently a large quantity of the mud and gravel along with the interspersed boulders must be swept away down into the dell at every season of flood. The matter thus removed will of course be still further comminuted in its passage, and at the same time will help to grind down the hard rock surfaces over which it is driven.