Geology. 217 



Besides this now classical topsy-turvey disturbance, there 

 are numerous faults and overlaps which may be briefly 

 touched upon; they are found to occur chiefly in the Palseozoic 

 rocks below, without affecting the Mesozoic covering above. 

 Amongst the chief may be enumerated the greatest fault of 

 the district, in the neighbourhood of Timsbury, Kilmersdon, 

 and Clandown, called the Great or 100 Fathom Fault. It 

 has a down-throw to the west varying from 120 to 720 feet. 

 The Farmborough Fault, with an up-throw or down-throw, 

 it is difficult to tell which, of 600 feet ; and the Overlap 

 Fault, running parallel with the Mendips at Radstock, 

 where it attains its fullest development. Mr. McMurtrie 

 states that in the under surface of the upper strata of the 

 part thrust forward, the fractured ends of the beds are 

 frequently bent downwards, — the upper surface of the strata 

 beneath being turned up, or forced into a succession of 

 smaller overlaps, by the immense mass shearing above. 

 {B. N. H. and A. F. C. "Proceedings," vol. i., p. 140). 

 Between these clearly defined lines, there exists a thick layer 

 of crushed materials of every kind. 



Next in ascending order comes what is called 



ong omera e. ^^ ,, ^^^ Ground," at the base of which 



is invariably found a more or less thick bed of Conglom- 

 erate, overlying the Coal Measures. This seems to be the 

 first break in the orderly sequence of deposits, and from 

 its position and contents, indicates a vast amount of denu- 

 dation. From a bed of only a few feet thick in the centre of 

 the Coal Basin, it increases to some 60 or 80 ft. southwards 

 nearer the Mendips ; the contained pebbles, also increase 

 in size in the same direction from that of small marbles to 

 rounded blocks 3 ft, in diameter. It rests, too, unconform- 

 ably on the upturned edges of the Pennant, the Carbonifer- 



