60 THE TRIAS AND OOLITE. 



THE chronicles of this period consist of a series of beds, 

 mostly calcareous, taking their general name (Oolite system) 

 from a conspicuous member of them the oolite a limestone 

 composed of an aggregation of small round grains or spherules, 

 and so called from its fancied resemblance to a cluster of eggs, 

 or the roe of a fish. This texture of stone is novel and striking. 

 It is supposed to be of chemical origin, each spherule being 

 an aggregation of particles round a central nucleus. The oolite 

 system is largely developed in England, France, Westphalia, 

 and Northern Italy ; it appears in Northern India and Africa, 

 and patches of it exist in Scotland, and in the vale of the 

 Mississippi. It may of course be yet discovered in many 

 other parts of the world. 



The series, as shown in the neighbourhood of Bath, is 

 (beginning with the lowest) as follows: 1. Lias, a set of 

 strata variously composed of limestone, clay, marl, and shale, 

 clay being predominant; 2. Lower oolitic formation, in- 

 cluding, besides the great oolitic bed of central England, 

 fullers'-earth beds, forest marble, and cornbrash ; 3. Middle 

 oolitic formation, composed of two sub-groups, the Oxford 

 clay and coral rag, the latter being a mere layer of the works 

 of the coral polype ; 4. Upper oolitic formation, including 

 what are called Kimmeridge clay and Portland oolite. In 

 Yorkshire there is an additional group above the lias, and in 

 Sutherlandshire there is another group above that again. In 

 the wealds (moorlands) of Kent and Sussex, there is, in like 

 manner, above the fourth of the Bath series, another addi- 

 tional group, to which the name of the Wealden has been 

 given, from its topographical situation, and which, composed 

 of sandstones and clays, is subdivided into Purbeck beds, 

 Hastings sand, and Weald clay. 



There are no particular appearances of disturbance between 

 the close of the Trias, and the beginning of the Lias and Oolite 



