12 



GBOLOOY Of TiriO AVON BASTN. 



the map, tlio only indication of its ])robable position on the 

 surface being a line of depression above a spring a little to 

 the west of Caswell Farm, together with that affoi'ded by 

 small springs and damp ground; and this notwithstanding 

 the fact that a difference of geological level of some thou- 

 sands of feet has been brought about by the fault. 



The rounded knobs of Mountain Limestone in the midst 

 of the Clapton Coal Measures stand out by reason of their 

 resisting power. They are, I believe, isolated fragments of 

 a once continuous limestone sheet. 



6. — The Greater Clapton FauU. 



The introduction of Coal Measures in thci Clapl-OTi district 

 can only bo explained by a groat fault which runs just to 

 the N. of the Clifton-Clevedon ridge in a W.S.W. and E.N.E. 

 direction. About a quarter of a mile E. of Naish ]Iouso, it 

 is either met nearly at right angles by another fault rnnniiig 

 nearly N. and S., or more probably here makes a shai'p 

 curve northwai'ds. Nowhere, however, so fai' as I know, can 

 the actual junction of the faulted rocks be seen. 



In a plan and section of the Clapton Coal Field by Mr. 

 David Llewellin, kindly forwarded me by Mr. Davis, of 

 Portishcad, this fault is very imperfectly indicated wii;h a 

 til row of not more than two or three hundred feet. In 

 another point, too, the diagram is unsatisfactory, and, I 

 think, misleading. It shows the Carboniferous Limestone 

 at a short distance (TjO or fiO yards) bcvlow the coal seams, 

 of which two arc marked ; this gives what I believe to be 

 a very erroneous impression. There can scarcely be a doubt 

 that beneath the Pennant beds in which the boring was 

 cari'icd, there lies the whole series of loiuer Coal Measures, 

 probably of a thickness of from 12 to 15 hundred feet. 



Let us try and estimate the throw of the fault. At tht; 



