LltHOLOGY. 7 i 



and harder material remain. The numerous falls of Wenslej-- 

 dale are, with only one conspicuous exception, over the different 

 bands of limestone : in the exceptional case, Millgill Force, the 

 edge rock is one of the firm gritstones of the Yoredale series. 

 Kisdon Force in Swaledale is over Limestone : the Caldron 

 Snout, the High Force, and the falls of Maize Beck and Blea 

 Beck over Basalt. Thomasson's Force and the other minor 

 falls of Cleveland are over hard edges of Inferior Oolite. 

 And almost invariably the fall is approached by a steep glen, 

 which, in course of time, the stream has excavated, along the 

 sides of which the cap-rock of the fall stands out in prominent 

 relief. 



