41 



There are numerous localities in the Bristol Basin where fuU 

 and complete evidence can be obtained as to the age of the 

 filling-in of these dislocations, as well as in the joints both of 

 the Limestones and Pennant ; and which I have no hesitation 

 in stating must have taken place during the entire period of the 

 destruction of the older rocks of the district by the New Eed, 

 &c. At Broadfield Down, between Bristol and the Mendip 

 Hills, at many places on the Mendips, such as Eber Eocks, &c., 

 Providence Place,* near Ashton (Bristol,) and numerous other 

 locahties where these Hydrous Oxides of Iron are worked, the 

 broad and exposed surface of the Carboniferous Limestones are 

 smoothed and planed away, having been laid bare through the 

 denuding influence of the New Red, as in the section Fig. 6. 

 Here and there in the depressions, occur the remains or remnant 



Fig. 6. — Section showing modes of occurrence of Fissures and Faults in the Carboniferous 

 Limestone, with patches of Dol. Conglomerate and New Red lying in hollows, &c. 



of the Dolomitic Conglomerata (lower member of the Trias, if not 

 older,) and the fissures and faults (almost always productive of 

 Iron) are associated vdth the Conglomerate, which frequently 

 fills them, the cementing matrix in some cases being the Brown 

 Haematite as well as the Dolomite. This phenomena occurs 

 both in the Carboniferous Limestone, Millstone Grit, and 

 Pennant, the qualities of the ore differing with the matrix 

 or rock in which it occurs. I may mention also that at Llan- 

 trissant and Llanharry, in Glamorganshire, the same conditions 

 occur in and on the Mountain Limestone. 



Faults. — ^We now come, however, to the deposits at Prampton 

 Cotterell, and the disturbed area north of that and on towards 

 Tortworth, where we find occurring three, if not four parallel 

 faults, all of which determine the presence of L-on at their 

 "backs" or "outcrop." These faults I have respectively named 

 the Cromhall or Mays Hill, Earn Hill, Eangeworthy, and 



* The Iron Lode in a fissure is here worked up the entire face of the hill. 



