Formation of Wealden Gorges. 473 



Fig. 34 is a section of a river perforating an escarpment from north to south. 

 The dip may either be north or south, without altering the form of the escarp- 

 ment streams S 1 to S VI flowing from E. to W. or W. to E. The Wealden 

 rivers flow with the dip ; the Avon, at Clifton, flows against. The strike, here 

 represented east to west, appears to be important, as, whatever the dip may- 

 be, the river enters the escarpment at a right angle. It can make most pro- 

 gress in denudation when it strikes the strata directly, and not obliquely. 



YS 



M A m 



%L s^'n. £ak. c i 1 I j " Mh 



1 v-. ■■■ -./.'.•■ /:-■ '■■/,■■;';'/-!< 



w 



■ ■;'■'■ 



54. 



The Streams S 1 to Svi are shown entering the side river, or banks, Vi to V VI 

 at an acute angle, and these enter the main stream, near R 1 also at an acute 

 angle. In a paper sent to the Institute of Civil Engineers, February 1872, the 

 author has discussed the question of river junctions. The stratum shown south 

 of the streams V 1 to V IV is intended for chalk, and is shaded so as to show the 

 higher elevation of the source of the streams, S 1 to S VI , in consequence of the 

 greater stability of the chalk, than those flowing from G, the Gault clay con- 

 taining those streams. It will be observed that the stream S 1 flows nearly 

 north, then west, and then south. The streams flowing off the Wealden 

 Escarpments take such a course that they, after a few miles, flow in an opposite 

 direction to that they first followed. Fig. 35 represents this general fact. The 

 height of the main stream at Vm depends upon the distance and relative levels 

 of the Watersheds, and of the point it discharges at into the sea or great river. 

 The longitudinal flexures of the pervious and impervious beds, and the general 

 direction of the side streams also, upon the quantity of water flowing, deter- 

 mine the exact position of the Weald and other rivers. The course of the side 

 streams is determined often by flexures of the strata and Watersheds, so that it 

 is a complicated problem, but not an impossible one, to find the theoretical 

 course of a river under certain known conditions. 



B'ia 3* 



East West 



This diagram shows the effect of transverse flexures on the Weald clay, or 

 Wealden valley, combined with similar flexures in the Lower Greensand, in 

 determining the particular points of the Wealden escarpments to be perforated 

 by the Wealden rivers. The rivers Wey, Mole, and Medway R 1 , R n , R IH , 

 flow at the bottom of the traverse binomial curves B 1 , B n , B nl . The great 

 flexure near Holdenborough, for instance, raises the Weald clay to a much 

 greater elevation there than at a point at Dorking. 



