BY THE PKESIDEJfT. 199 



A river, assuming that it were liable to floods of this kind, 

 would constantly scour out its bed, — deepen it by transporting 

 the materials to the sea, or by removing them and depositing them 

 in fresh places. In that manner small portions of the original 

 bed of the river which had escaped the action of succeeding floods 

 would be left as land-marks at the side of the valleys at a far 

 higher level than the beds now being formed at the bottom of the 

 valley — in fact, the old river-bed would be cut through and small 

 portions left as memorials of its existence at high levels. That 

 such is the case with the gravel-beds now 90 or 100 feet above 

 the streams is also borne out by the fact that above the gravels 

 we find the fine silt or brick-earth already mentioned. Gravel 

 can only be carried by water flowing with considerable velocity. 

 Where the velocity is not so great, it is deposited; where water 

 flows slowly, sand falls to the bottom ; and where it is nearly 

 stagnant, turbid water will deposit mud. All these deposits 

 might be formed at the same time, the gravel along the bed of the 

 main stream, and silt and mud at spots only accessible by flood- 

 waters. At the period when the rivers ran at a high level, the 

 bottoms of the valleys were probably much wider than at present, 

 and you may readily conceive how from any meandering of the 

 streams from one side of the valley to the other, parts of the old 

 bed were left at some distance from the main stream, which were 

 liable to receive a coating of sand, and subsequently, as the river 

 got further away, were merely exposed to the almost stagnant 

 waters of floods, and received a coating of brick-earth. 



And not only have we the evidence of this great deepening of 

 the valleys, which must havp required an enormous amount of 

 time ; but we have that curious feature, to which I have already 

 alluded, of gravels of fresh-water formation capping the cliffs on 

 the south coast of England. At Bournemouth the cliffs are about 

 ninety feet high, with this gravel above, and, judging from analogy, 

 we cannot but regard it as having been formed in the bed of a 

 river. But the southern side of the valley through which that river 

 flowed has now entirely disappeared, and in order to reconstruct the 

 country through which it flowed, you must regard the great range 

 of Chalk hills which passes through the Isle of Wight as being 

 continuous to Ballard Down, near Corfe Castle, and flll up the 

 great bay between Studland and the Isle of Wight with one 

 hundred square miles of high ground sloping to the north. 



That this was in all probability the early condition of that 

 part of England, and that the capping of the cliffs at Bourne- 

 mouth is merely the bed of an ancient river, is shown by 



