444 



Maw — On Suhaerial and Marine Denudation. 



ridges, as at eb, Fig. 3, or co, Fig. 4, will be cut through. ; denudation 

 may proceed over ridge and valley, and gradually lower the entire 

 surface to f f, after having removed the whole of the newer deposit, 

 and will impress on the old deposit a contour partaking of that of both 



Fig. 4. — Longitudinal Section of Ancient Valley System. 

 Section of Superimposed System. 



Tkansverse 



the old and neiv surfaces, the association of the general system of 

 valleys with transverse gorges having had their origin on different 

 surfaces and which could not be accounted for on any single simple 

 system of waterflow. 



Fig. 5. — The dotted line represents the ancient buried "Watercourses, and' the dark" 

 lines those on the new overlying surface. 



The unequal resistance of old and new deposits may also introduce 

 complicated systems of contour ; for instance, in the case of the valleys 

 in the softer upper deposit (cc, Figs. 4) running transversely to the 

 ridges of the older underlying formation, the transverse ridges would 

 be gradually cut through, and, as the level of the older valleys was 

 approached, an outlet would be formed for the progressive excava- 

 tion of the softer deposit filling them up, and the old valleys would 

 be restored, connected by the transverse gorge which played so im- 



