must have been at some remote period the old coast-line, the task is rendered difficult and within certain limits impossible by the absence of any evidence as to the elevation above the sea of the land removed, and as to the channels along which the sea could work. In this case, however, there is a strong presumption as to the unbroken continuity of the chalk-range, and of its elevation having been much the same throughout, as it now is at both ends of the breach. The general character of the beds above the Chalk, so far as their power of resistance to water-action goes, seems also much the same at either extremity; though perhaps the beds at the Isle of Wight end of the breach are somewhat the harder. Assuming nearly equal conditions, and looking at the form of the present coast-line, which is indented by two distinct broad bays, it seems probable that the old course of the river may have been intercepted by the sea at two several points, the one nearer Poole and the other nearer Lymington. Directly this closer communication with the sea was formed for the Dorsetshire rivers, they would, of course, owing to the more rapid fall, excavate their valleys with greater speed at their mouth, and directly they became tidal, the sea would make rapid inroads on the soft sand and clay exposed to its action. So effective is this action, that at Hordwell Cliff the waste of the shore is said to be now going on at the rate of about a yard per annum,[1] or upwards of half a mile every thousand years, though perhaps this is somewhat exaggerated.
In discussing this question, I have purposely avoided complicating the subject with the effects of any general lowering of the surface of the ground by erosion either chemical or mechanical; or of upheavals and depressions of the land during the period of the formation of the valleys, though no doubt this also has taken place, especially along the southern coast of Britain. I must, however, mention the existence of a submerged forest, occasionally visible at low water, at the foot of the cliffs at Bournemouth, which seems to show that there as elsewhere a depression of a former land surface has taken place. The late Mr. Albert Way, F.S.A., who had the opportunity of examining some of the stumps of trees exposed at rare intervals at low water, informed me that they appeared to be those of the true Scotch fir; and also that local tradition speaks of an impassable morass having, so late as the commencement of the present century,
