68 



PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



through a deep railway- cutting, the rails being 80 feet below the 

 surface of the ground, and 112 feet below the adjoining peak of 

 rock at D. 



The escarpment of rock is shown to slope about 43° N., at the 

 northern end of the cutting, B, close to the viaduct, and only about 

 20° at the southern end, D. Gravel with boulders of Old Eed Sand- 

 stone, and many other rocks, is spread over the surface of the rock 

 at D, up to a height of 200 feet above the river TafF. 



Fig. 4. — Enlarged Section of Gravel Deposit. 



Fig. 4 is an enlarged view of the section at B along the line of 

 railway, showing the gravel lying in a concavity of the rock forming 

 a part of the Taff valley, at very high angles. Near the rock the 

 dip of the gravel is 35°, gradually becoming less steep until it reaches 

 18°. The gravel below the rails is not exposed at this point. It 

 wiU be seen that fig. 4 should have been reversed, to accord with 

 PL ly. fig. 1 ; it is on the natural scale. 



Fig. 5 is a transverse section at right angles to Plate lY. fig. 1 , 

 and fig. 4, showing the railway- cutting at the point D. As it is 



Fig. 5. — Section across the Taff- Valley Baihuay. 



510. 



505. 



EaJls 393 feet. 



not sloped, it gives a good opportunity of studying the position of 

 the gravel, particularly as the surface of the rock is clearly exhi- 



