58 



This estimate differs only in the thickness of the pennant 

 from the estimate made at the Shepton Mallet meeting 

 of the Somersetshire Society, recent explorations having 

 proved it to be thinner than then stated. 



So far we have considered the carboniferous system as it 

 probably exists in the centre of the basin, where it attains its 

 greatest vertical depth. I would now, in conclusion, say a few 

 words as to the construction of the section laterally. With re- 

 gard to the central portion of the section between Farringdon 

 and the old Dunkerton Collieries, there is little room for doubt. 

 It has been proved by pits sunk at regular distances between 

 those two points ; and that part of the section, therefore, 

 embracing as it does nearly the whole of the upper division, 

 may be taken as substantially correct. The eastern and 

 western parts, however, being more uncertain, I have shown 

 the strata in dotted lines, and it is necessary that I should 

 explain the evidence on which that part of the section is 

 founded. To begin with the western end, the only exploration 

 to the west of Farringdon is a trial pit, which was sunk many 

 years ago, in the village of Chewton. In this shaft, after 

 passing through some 35 fathoms of conglomerate, a boring 

 was put down for 180 feet in a hard stone, said to have been 

 the mountain limestone. We have no further data until we 

 reach the outcrop of the moimtain hmestone and old red 

 sandstone, on the Mendip Hills. 



In the absence of better information, I have taken the out- 

 crop of the under part of the limestone, and extended that 

 formation downwards at its estimated thickness and at the 

 proper dip. I have then shown the millstone grit at its 

 estimated thickness, and in this way I have arrived at the 

 conclusion that the borehole cannot have been in the hme- 

 stone, as asserted, but more probably in the millstone grit. 

 In the section, the borehole is shown in the upper part of the 

 grit, and this agrees with the statement of one of the sinkers, 



