48 



PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



of trap and other rocks, that he has been led to draw up a sup- 

 plement to his former papers. 



The Mountain Limestone of Bleadon Hill and that of Uphill 

 have been disconnected by two great downcast faults since the 

 lias was deposited, that on the Bleadon side ranging E. by N. and 

 W. by S., and that on the Uphill side N. E. and S. W. In the 

 space between them, which is about a quarter of a mile broad, the 

 surface consists of lias and new red sandstone. 



In the cutting the Bleadon fault is finely exposed, and its 

 southern side presents a great slickenside wall of limestone and 

 trap, which dips to the south at an angle of 70°. On the northern 

 side of the fault, the lias is seen, curiously faulted, to some little 

 distance ; it then dips considerably towards . the fault, the in- 

 clination increasing, and the beds at last going down with the 

 fault, the lias inclining towards it at an. angle of 45°. The lias, 

 where abutting against the trap, has no appearance of having 

 been altered by it. 



Section I. 

 Western side of Railway. 



p a 



a. Mountain limestone. 

 a'. Altered mountain limestone. 



On the western side of the Railway, not far from its northern 

 end, an insulated mass of Mountain limestone is seen standing 

 several feet in advance of the vertical cutting. Though much 

 altered and deprived of the usual planes of bedding, it may readily 

 be identified by its nodules of chert and crinoidal stems and plates. 



Little doubt can be entertained that it was once the continuation 

 of four thick beds, which rest on its southern flank, and in the 

 process of quarrying have separated from its surface. Nearly half 

 the base of this insulated mass of limestone has been removed, and 

 replaced by trap, the surface of contact between the two being 

 very rough and unequal ; and a foot or two further towards the 

 north there rises from beneath this altered limestone a mass of 

 trap, 9 feet thick at its base, which, as it ascends, gradually tapers, 

 and at the height of from 20 to 25 feet is reduced to a thin striug, 

 or enters into joints of the limestone. The limestone is highly 

 altered, and the limestone walls of the joint are singularly rough 

 and rugged throughout. The limestone is traversed by a long, 

 narrow, irregular crack, in which are found thin seams and plates 

 of trap and trappean matter. 



Fifty-four feet to the south of the first mass of trap, another 

 irregular mass of the same rock shows itself, and ascends through 



