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Show 300 EOCENE PERIOD. [Ch. XXI. the line, whet·eby the effect of a double axis of elevation was in some measure produced. In order to O'ive a clearer idea of the manner in which the b chalk-hills at·e intel'sected by these transverse valleys, we subjoin a sl<etch (No. 73) of the gorge of the river Adur, taken from the summit of the chalk-downs, at a point in the bridle-way leading from the towns of Bramber and Steyning to Shoreham. If the reader will refer again to the view given in a former wood-cut (No. 65, p. 290), he will there see the exact point where the gorge, of which we are now speaking, interrupts the chalk escarpment. A projecting hill, at the point a, hides the town of Steyning, near which the valley commences where the Adur passes directly to the sea at Old Shoreham. rrhe river flows through a nearly level plain, as do most of the others which intersect the hills of Surrey, Kent, and Sussex; and it is evi. dent that these openings, so far at least as they are due to aqueous erosion, have not been produced by the rivers, many of which, like the Ouse near Lewes, have filled up arms of the sea, instead of deepening the hollows which they traverse. In regard to the origin of the transverse ravines, there can be no doubt that they are connected with lines of fracture, and perhaps, in some places, there may be an anticlinal dip on both sides of the valley, as suggested by a local observer *. Dut this notion requires confirmation. No. 74. fj I I• S11pposed section of Transverse Valley. '!'he ravine, called the Coomb, near Lewes, affords a beautiful example of the manner in which narrow openings in the chalk may have been connected with shifts and dislocations in the strata. '!'his coomb is seen on the eastern side of the valley of the Ouse, in the suburbs of the town of Lewes. The steep "' Martin, Geol. of Western Sussex, p. 64, plate 111. fig. a. Ch. XXI.] TilE COOMJl, NE:\R LEWES. 301 declivities on each side are covered with g1·een turf, as is the bottom, which is perfectly dry. No outward signs of Jisturbance are visible, and the connexion of the hollow with subterranean movements would not have been suspected by the geologist, had not the evidence of great convulsions been clearly exposed in the escarpment of the valley of the Ouse, and in the numerous chalk pits worked at the t~rmination of the No.75. Tltc Coomb, ncar L ewes. Coomb. By aid of these we discover that the ravine coincides precisely with a line of fault, on one side of which the chalk with flints a, appears at the summit of a hill, while it is thrown down to the bottom on the other. I I Fault in tlte cliff-hills near Lewes. a, Chalk with flints. b, Lower chalk •. The fracture here alluded to is one of those which run east • I examined this spot in company with Mr. Mantell, to whom I am indebted for the above sectioui |
