330. The mouths by which rivers on bold rocky coasts discharge their waters into the sea, afford a very striking confirmation of the conclusions concerning the general system of waste and degradation which have been drawn above. At these mouths we usually see, not only the bed of the river, but frequently a considerable valley, cut out of the solid rock, while that rock preserves its elevation, and its precipitous aspect, wherever it is not intersected by a run of water. No convulsion that can have torn asunder the rocks; no breach that can have been made in them, antecedent to the running of the waters, will account for the circumstance of every river finding a corresponding opening, by which it makes its way to the sea; for that opening being so nearly proportional to the magnitude of the river, and for such breaches never occurring but where streams of water are found. 331. The actual survey of any bold and rocky coast, will make this clearer than any general statement can possibly do. Let us take, for an example, the coast of the British Channel, from Torbay to the Land's End, which is faced by a continued rampart of high cliffs, formed of much indurated and primeval rock. If we consider the breaches in this rampart, at the mouths of the Dart, of the Plym and Tamer, of the river at Fowey, of the Fal, the Hel, &c. it will appear perfectly clear, that they have been produced by their respective streams. Where there is no stream, there is no breach in the rock, no softening in the bold and stern aspect which this shore every where presents to the ocean. If we look at the smaller streams, we find them working their way through the cliffs at the present moment; and we see the steps by which the larger valleys of the Dart and the Tamer have been cut down to the level of the sea. If we would have still clearer evidence, that no breaches made antecedently to the running of the rivers have opened a way for them, we need only look to the opposite side, or northern shore, of the same promontory, where we also find a series of outlets, all originating in the ridge of the country, and becoming deeper as they approach the sea, but altogether unconnected with the openings on the south side; and this could hardly have been the case, had they been the effects of previous concussions, or of any peculiarity in the original structure of the rocks.