Dr. FiTTON on the Strata below the Chalk. 151 



through the platform of the sands, on the north and west of Godalming, receiving several stream- 

 lets by the way. But there, instead of continuing its direction, it turns suddenly to the north ; 

 and receiving another branch from beyond Cranley, far within the valley of the Wealds, cuts 

 almost directly across both the green-sand and the chalk, and makes its way to the Thames at 

 Weybridge. The mere closing-up of the defile at the mills on the north of Godalming, would 

 convert the whole of Pease-marsh, Frensham, and Thursley commons into a lake : — and, on the 

 other hand, a slight excavation towards the north, through Frensham to the river, would drain the 

 great pond there. 



The sudden change in the direction of the Wey, near Farnham, is the more remarkable, as the 

 Blackwater, which rises on the northern slope of the chalk downs between Farnham and Alder- 

 shot, about two miles from the angle of the Wey near the west end of the Hog's-back, runs on 

 the Bagshot sands, towards the north and west, by Frimley, Blackwater, &c., to join the Lodden, 

 not far north of Strathfieldsay, in its course to the Thames near Shiplake. The line of the Wey, 

 therefore, from Alton to Farnham, is nearly a continuation of that of the Blackwater* ; the two 

 streams being separated only by the prominence of the chalk between the Hog's-back and the 

 foot of Tucksbury Hill f. 



The gorge of the Wey is nearly opposite to that of the Arun, on the south of the Wealden, one 

 branch of which runs almost directly north and south, from a point between Loxwood and Slin- 

 fold, to the sea at Little Hampton ; and the structure of the two rivers is very much alike. 

 The Arun rises in the centre of the Wealden tract, whence it runs directly to the sea; as does 

 the Wey from Cranley : but it receives, near Pulborough, at right angles to the main stream, 

 the copious branch (if it be not rather itself the principal stream,) called the Rother ; which, 

 having risen near the ponds of Wolmer Forest, very near the sources of the Wey, and followed the 

 curves of the denudation for more than twenty miles, in the trough between the chalk escarpment 

 and the Lower green-sand, is then carried suddenly out of that direction, and withdrawn from the 

 valley of the Weald. 



(67.) From whatever cause the transverse course of the streams may have 

 orig-inated, the relative composition of the strata was favourable to their retain- 

 ing that direction^ when once they had made their way across the chalk and 

 Upper green-sand. For, as the lower beds of the chalk itself^ and still more 

 the Gauit, are remarkably retentive^ while the upper chalk is permeable by 

 water, — the slope of all the strata being outwards, or from the central ridge 

 of the valley, the whole of the waters imbibed by the chalk would be deter- 

 mined outwards, if any pervious channel were opened at its bottom. And if 

 a fissure were cut through the whole series, without great vertical displace- 

 ment, the retentive beds of the chalk-marl and clay, would immediately re- 

 unite, and close it below; while, the chasm in the chalk above remaining open, 

 a permanent drainage outwards would be produced, and the break would be 

 continually enlarged. 



* The main stream of the Wey is that which runs direct from Wolmer to Shalford. Seethe map. 

 •\ It should, however, be kept in view, that the bed of the Blackwater hereabouts is several 

 feet above that of the Wey. 



