314 



GEOLOGY OF THE BRISTOL COAL-PIELD. 



changing into pure massive limestone, and ending in many hundred 

 feet of grits and sandy beds. In several localities to be subsequently 

 described, we find these limestone beds forming immense hollows 

 many miles in diameter that were afterwards filled up by stores of 

 coal, which now constitute directly, or indirectly, so great a source 

 of our national prosperity. Here a^d there we find some exercise 

 of terrestial force has disjointed and displaced immense thicknesses 

 of rocks, dislocating and twisting them into the most fantastic 

 shapes. Perhaps the most remarkable of these faults, and one that 

 is most fully displayed, is that on the north bank of the Avon. Here 

 is a displacement, vertically, of more than eight hundred feet, 

 dividing the Clifton series into two parts, sinking the one and 

 upheaving the other, till we see apparently, as we walk down the 

 river side, two sections of the same beds. This is explained roughly 

 by fig. 14. 



Fig. U.^Clifion Fault. 



a Massive Limestone. — h Upper Limestone Shales. — c Millstone Grit. — 

 d Magnesian Conglomerate. 



The destruction caused by this tremendous convulsion was still 

 more intensified by concluding with an awful lateral pressure which 

 crushed the broken rocks into contortions, mixing them with later 

 formations in the utmost confusion. 



"With broken masses of limestone we [see millstone grit, marls, 

 magnesian conglomerate, and beds of coal mingled together without 

 the slightest reference to order of deposition. Any one walking 

 past this spot will see an unrivalled section more than three hundred 

 feet thick and a quarter of a mile long. 



