150 THE STORY OF THE EARTH. 



CHAPTER XVI. 



THE OOLITES. 



The Oolites are granular limestones of limited 

 extent, contained between clays, which in Great 



Britain range between Dorsetshire and the north 

 coast of Yorkshire. They form three limestone 

 terraces in the south of England, each of which 

 rests on a clay, and hence have sometimes been 

 named Lower, Middle, and Upper. It is more 

 convenient to adopt two divisions. The Lower 

 Oolites include every bed above the Lias to the 

 Cornbrash. The Upper Oolites extend from the 

 Oxford Clay to the Portland Oolite. 



Lower Oolites. 



The Midford Sands are seen near Bath making 

 the base of the Oolites. The sand appears to have 

 been derived from the south, because the whole 



of the Lower Oolites are represented by sands in 

 Dorsetshire. The Midford Sands disappear to 



the north of the CotSWOld Hills, probably bee. 



they ar< sen ted there by clay which is 



distinguished from the 1 ias. 



The beds named Northampton Sat ur in 



the same geological position in Northampton- 

 re. They are about 70 feet of brown sands 



and yellow sandstone, with ironstone, which is a 



valu l hey are capped by grey and 



white sand, containing beds of lignite, which may 



mutated in an estuary. Their tossils 



mainly those of the Inferior Oolite; and they 



bably a iphical continuation oi the 



