OOLITE. Q\ 



red stripes.* A similar bed of slate-clay occurs njider the chalk in 

 the north of Ireland, containing thin s^ms of argillaceous limestone, 

 with petrifactions of the same kind with those in our upper shale. 

 In most places, however, a bed of what is termed green sand is inter- 

 posed between the clay and the chalk. The greenish colour of the 

 lower part of our chalk, may make some fancy it to correspond 

 with the green sand; but it can with no propriety be called sand, for 

 it is not arenaceous. Thfe bed of slate-clay, with seams of argillace- 

 ous limestone, noAV mentioned, has been termed lias.\ 



The shale bed, like the chalk above it, must vary considerably 

 in thickness; but it is probably not more than between two and three 

 hundred feet thick, if it ever exceeds two hundred. It is thickest, 

 as may be expected, behind the highest part of the Wolds, as at 

 Settrington. There it may be traced to a considerable distance down 

 a steep bank ; though in several parts of the bank, particularly at the 

 foot where the declivity is gentle, it is covered by the alluvium, which, 

 filling the bottom of a narrow valley through which a small stream 

 flows, conceals the junction of the shale with the next member of 

 our strata, viz. 



THE OOLITE. 



The cliffs in Filey bay furnish no evidence respecting the beds 

 that immediately succeed the upper shale; for behind the shale Ave 

 find nothing but an alluvial cliff, extending from thence to the rocks 

 called Filey Bridge, a distance of above two miles, in which the 

 regular strata are wholly interrupted. At Settrington, however, and 

 along the eastern skirts of the Langton Wolds, we find the slate-clay 

 succeeded by that remarkable kind of limestone called oolite or 



* Geological Transactions, III. p. 243, 248, 249. f IWd. p. 164, 165, 911, &c. 

 Q 



