Page:Quarterly Journal of the Geological Society of London, vol. 27.djvu/105

 because, though composed of angular flint and Tertiary pebbles, the stream that passes Willesboro', a tributary of the Stour, does not reach any way near to the chalk escarpment, while pits in the Lower- Cretaceous stone are close at hand. In striking contrast with this Willesboro' gravel is the gravel skirting the Stour at lowest level at Bucksford, less than three miles west from that at Willesboro'. This low-lying gravel is entirely made up of subcretaceous material, though by long search a solitary fragment of flint may be found in it, derived probably from the flints scattered over the Gault surface, up to which some of the rivulets running into the Stour extend ; it is obviously a deposit of the Stour when flowing in greater volume in the same direction as at present. But, looking at the physical and geological features of this part of the Weald, can it be contended that a similar flow at from 50 to 100 feet higher level could have deposited gravel of such opposite character to this as is that hard by at Willesboro' or that, about 15 miles distant, on the heights at Canterbury ?

I would, however, prefer to deal with the possibility of these pebbles reaching such positions on broader grounds than the precise position of the rivulets nearest to their place of occurrence ; that is, I regard their position as repugnant to any introduction from the Stour or Medway, in their present direction, during the course of a prelonged atmospheric or fluviatile denudation which resulted in the prosent excavation forming the Weald, for the following reasons, viz. : —

1st. The form and character of the great Wealden denudation area (or major valley), as distinguished from the valleys proper of the Wealden rivers (or minor valleys), is diametrically opposite to any that can result from river-action, because, however great we concede the power of that action to be, any excavation resulting from it must be conterminous with the excavating agent itself (the river and its tributaries), since every stream, large or small, can only deepen its own proper valley, and the result cannot be any such excavation as the major valley of the Weald, with its well-known contour and escarpments, but only a series of valleys, or minor excavations, ramifying in the directions in which the stream extends, and in some degree at least coinciding with them; and the longer this action is continued, the deeper and more distinct must these features become.

2nd. If flints and pebbles were derived from the Chalk escarpment, we should look for an increase in their number as the escarpment is approached ; but though a few angular flints are in some places scattered over the surface of the Gault, the Lower-Tertiary pebbles seem wholly absent from that part of the area, and from the sources of the streams supposed by some to have brought them.

3rd. The Lower-Tertiary beds yielding pebbles are far away from the escarpments, and rest on the northern extremity of the chalk slope and below the crests of the escarpments ; and however high the level be to which we carry our imagination of the flow of the Wealden rivers in past times, even if up to the level of the escarpment-top itself, still the drainage from the Lower-Tertiary strata must at all times have flowed away from the scarp, and not into the Weald. There are, however, some patches of pebble-beds (of date