14 OKOLOCiY Oil' TIUO AVON ISAHIN. 



taut 2); iiiilcR, or say 12,()()() foot N. N. W. from fho Cliftoii- 

 Clcvedon ridge at the point where the fault curves off to the 

 N. The average angle of dip may be taken at 20°. With 

 these data, viz., the distance and the angle of dip, wo can 

 estimate approximately the amount of vertical displacomoiit 

 of the strata. It is 4,104 foot; and since the average angle 

 of dip is probably greater than 20°, wo may, I think, take 

 4,000 foot as a minimnm estimate of the tlirow of the fault 

 at the eastern end. At the same time 1 should mention that 

 the state of disturbance of the strata in the neighboiirliood 

 of Portishead leads me to place very li(t,lo reliance on this 

 mode of estimating the amount of vertical displacement. 



As we pass westwards towards Clevedon, the throw 

 becomes less and less. Tliis is clearly seen by the gradual 

 approximation of the Portlshcad-CIovedon lidge and the 

 Clifton- Clevedon ridge. At Clevedon the two ridges moot; 

 the fault has so nearly died out westwards as not to bo 

 sullicient in amount to soj)arato limestone from limostono. 



6. — l%o Lesser Clapton Fault. 



The existence of bosses of Mountain Limostono in the 

 midst of the Coal Measures at Clapton is at first sight not 

 a little strange and puzzling. I make use of the ()-inoh. 

 ordnance map on which to note my detailed geological 

 observations ; and I find that my " M. L. 2r)°S.W.," record- 

 ing an observed dip of Mountain Jjimestone, is wedged 

 tolerably closely in between two notes, "Old Shaft (Coal)," 

 printed on the map. So, too, in the I'oad loading h'om 

 Clapton to Clapton Church, there is cleai- evidence of coa,l in 

 the bank ; while at a higher level, and within (30 yards, is 

 Mountain Limestone quietly dipping at a gentle angle (14°) 

 towards the moor ! 



Puzzling', hovvevof, as this Mountain Limestone in the 



