368 GEOLOGY OF THE ISLE OF PURBECK. 



the most combustible beds of these substances 

 are commonly known as the Kimmeridge Coal.* 

 " This coal," observes Mr. Webster, " is merely 

 a slaty clay strongly impregnated with bitumen, 

 and does not exhibit any signs of vegetable 

 structure. It burns very readily with a brisk 

 flame, affording a good heat, but emitting a very 

 disagreeable smell. "-j- 



Beneath the bituminous beds, are clays, shales, 

 and thin bands of limestone, containing the Ostrea 

 deltoidea, Ammonites triplex, Grypliea virgula, and 

 other shells characteristic of this division of the 

 oolite formation. 



South-west coast of Purbeck. — We have 

 now arrived at that part of the coast, where the 

 range of vertical chalk, of which we examined 

 the eastern extremity at Ilandfast Point, appears 

 in the inland recesses of several little bays or 



* At Chilley in Sussex, sandstone strongly impregnated with bitumen 

 (called " pitchstone" by the neighbouring peasantry,) and much resembling 

 in appearance some of the Kimmeridge beds, is found beneath the silt in 

 Pevensey levels. It is described in " the Fossils of the South Downs," p. 76. 

 I have not been able to examine this bed in situ; it probably belongs to the 

 Wealden formation. 



t Sir H. Englefield's Isle of Wight, p. 187. I, may here notice that there 

 are often found at Kimmeridge, Encombe, and the surrounding neighbour- 

 hood, circular pieces of shale- which have evidently been turned in a lathe. 

 They are of the size of a half crown, and have a few circles drilled partly 

 through on one side; they are termed by antiquaries, "coal-money," and 

 are supposed to have passed as tokens in ancient times — perhaps they were 

 current only in the peninsula. Several are occasionally found carefully 

 I'n 1 1. .1 beneath two stones. 



