Chalk Bluffs of Trimmingham. 



309 



the majority are only half silicified, being hollow or partly rilled 

 with a grey chalky matter, which is gritty to the touch and is 

 full of sponge-spicules and minute organisms. The flints 

 are moreo ver surrounded with similar greyish chalk, which 

 sometimes forms a band connecting two or more together ; 



Northern Bluff, Trimmingham, 1875 . 



this greyish chalk also occurs in places without enclosing any 

 flinty matter, and gives a mottled appearance to the mass. 

 Between the layers of flint nodules the rock is full of a small 

 curved species of oyster (since identified as Ostrea lunata, 

 Nilss.) ; Belemnitella mucronata is also common ; and there are 

 many other fossils (see posteh) ; but the best specimens are 

 adherent to the flints. 



If the measurements above given be compared with those 

 of Sir Charles Lyell, and the mass in its present state (fig. 1) 

 be compared with the figure in the early editions of the 

 c Principles of Geology' (reproduced in fig. 2), it will be seen 

 that it has now only one third of the length it possessed in 

 1839. Originally the front face seems to have exhibited a 

 complete synclinal curve, with more than half of the corre- 

 sponding anticlinal at the southern end ; but now only the 

 centre of the synclinal is left, the beds rising very slightly to 

 the southern, and more decidedly towards the northern end. 



With regard to the dip of the beds as viewed from the sides 

 some difference of opinion has existed. It is seldom, indeed, 

 that a clear section is presented by the side face ; for the chalk 



