144 



intervening Vobster series and millstone grit, and this un- 

 usual space seems to be occupied by fragmentary portions of 

 the Vobster series, the more valuable parts of which are com- 

 monly to be found in their natural position closely adjoining 

 the Mendip range. 



In the case of the mountain limestone there is a remark- 

 able exception to what I have stated to be the general rule. 

 In looking over geological maps of the neighbourhood, many 

 may have observed near to Upper Vobster, two isolated patches 

 of it which are entirely surrounded by coal measures. In the 

 earlier ordnance maps these were represented as having been 

 faulted up through the coal measures, and comparatively re- 

 cently the same view has been taken in another quarter ; but 

 I am in a position to prove that the workings of at least one 

 colliery have been extended beneath the limestone, and that 

 several wells have been sunk through it, so that the fault 

 theory of the Government geologists must have been a mis- 

 take. If, then, the limestone has not been thrust up through 

 coal measures, but on the contrary rests upon them, we are 

 bound to infer that the same disturbance which folded the 

 coal measures back upon themselves carried with them these 

 enormous masses of limestone, which are thus found half a 

 mile from the parent rock. 



Before closing I would ofier a few remarks on 



THE APPROXIMATE DATE AND PROBABLE ORIGIN 

 OF THE FAULTS AND CONTORTIONS 



described, and it is necessary that these should be connected, 

 because they have a direct bearing on each other. 



According to the testimony of the best authorities, the up- 

 heaval of the Mendips must have occurred towards the close 

 of the carboniferous period, and prior to the deposition of the 

 triassic beds, and it is a circumstance worth noting, that 

 with hardly an exception the dislocations which have broken 



