346 a. E. Sippisley — Somersetshire Coal-measures, 



solution of some of tlie numerous difficulties at present standing in 

 the way of a satisfactory understanding of this extremely com- 

 plicated district. 



The commonly accepted structure in Somersetshire is taken to be 

 as follows — in descending order : — 



1. The Radstock measures, supposed to be wanting in Gloucestershire and stated 



to have been removed by denudation there. 



2. Beds of red shale, traces of which are supposed to exist in Gloucestersbire near 



the top of the Coal-measures there. 



3. Farrington measures, supposed equivalent to the Gloucestershire upper series 



measures. 



4. Pennant. 



5. Lower series Coal-measures. 



6. Millstone Grit. 



7. Carboniferous Limestone. 



All, of course, more or less disturbed by faults, but still in the above 

 order; and this general relation of the Coal-measures in Somerset- 

 shire to those in Gloucestershire is supposed to be thoroughly well 

 established. 



It may be as well to allude briefly to some of the causes which, 

 make these Coal-measures peculiarly difficult to study in such a 

 manner as to be certain that the results arrived at are free from error. 



About five-sixths of the Bristol Coal-field are concealed by newer 

 formations, rendering it impossible to trace the measures, or the 

 position of the numerous faults of an older date than these newer 

 formations, on the surface ; the sole information obtainable, when 

 the Coal-measures are not exposed, being from the workings at the 

 different collieries. 



These workings at different places have in many cases not been 

 connected by accurate instrumental measurements, but often only 

 in a vague and general way, and by assuming perfect regularity in 

 the strata between the separate workings, when perhaps the very 

 contrary may be the case. 



Absence of records showing the full details of pit sections ; the 

 only information obtainable now, concerning many of the older 

 sinkings, being the simple intervals between the seams. Also, 

 faults cut through in the shafts do not always appear in the sections. 



Correlation of the seams has occasionally proceeded in rather a 

 haphazard manner, the seams being named first, sometimes without 

 nearly sufficient evidence as to their identity, and then the names 

 traced from one colliery to another as if the correlation were un- 

 doubtedly correct. 



The correlation would have been much more reliable if the full 

 detailed sections had been taken into account instead of merely 

 fancied resemblances and qualities and thicknesses of the coals 

 alone, all often extremely variable in comparatively short distances. 



The faults of the district are extremely numerous, those shown on 

 the Geological Survey being, although by no means few, only a 

 portion of them, complicated, and with throws often very consider- 

 able, and where the throw of a fault is, as usual, calculated by the 

 amount of displacement of a seam bearing the same name on each 



