128 



GENERAL FEATURES OF THE COAL FIELD. 

 In order that the bearing of the present paper may be the 

 better understood, it may be well that I should at the outset 

 refer again to the section of last year, and that I should in a 

 word or two explain the general features of the district. The 

 carboniferous rocks of Somersetshire, you will observe, rest 

 upon the old red sandstone with which they are probably 

 approximately conformable. They are well represented in 

 this district ; the mountain limestone, the millstone grit, and 

 the true coal measures being all present. The latter, with 

 which we have principally to deal to-night, are composed of 

 two great divisions, separated by an immense thickness of 

 sandstone known as the pennant rock. The upper division 

 consists of the first, or Radstock, and the second, or Farring- 

 don series, these being divided by a thick intervening stratum 

 of red shale. The lower division contains the third, or New 

 Rock, and the fourth, or Vobster series ; the veins of the 

 former being contained in hard sandstones, while those of the 

 latter are usually associated with exceedingly tender shales. 

 Above the coal measures, and resting unconformably upon 

 them, are the secondary rocks ; but the disturbances which 

 we have now to describe were mostly formed before the 

 deposition of these strata, and rarely aflfeet them. 



FAULTS AND CONTORTIONS. 



Whatever may have been the conditions under which the 

 coal measures were originally deposited, there can be no 

 doubt that they have subsequently been exposed to an 

 amount of disturbance and dislocation so tremendous that 

 when we try to realise the state of things then existing, we 

 seem to pass into the region of romance rather than reality. 

 In a paper recently contributed to the Geological Society, 

 Mr. Moore has described in a striking manner the circum- 



