H. E. Sippisley — SomersetsJiire Coal-measures. 347 



side of the fault, it results that if the seams should happen to be 

 wrongly correlated, the throw of the fault may be very different to 

 that which it is supposed to amount to. 



Uncertainties as to whether certain Coal-measure sandstones are 

 true Pennant, or should be taken as belonging to other geological 

 horizons. 



Contemporaneous denudation having removed certain strata and 

 seams of coal, possibly not long after they were formed, the seams 

 being sometimes replaced by beds of sand, etc. 



There are many other difficulties in the way of satisfactory 

 correlation, on which it is not necessary to dwell further, as they 

 soon present themselves only too plentifully to any investigator of 

 the subject. It may be briefly stated that the structure of the district, 

 generally, is so much the reverse of regular, that instances can be 

 pointed out in which the strata met with at the bottom of a tolerably 

 deep shaft are the same that had already been passed through at 

 the top thereof; and in further illustration of the amount of dis- 

 location the district has suffered, allusion may be made to a locality 

 where, by simply crossing the breadth of a turnpike road, Old Eed 

 Sandstone may be found on one side, and Coal-measures on the 

 other; the Lower Limestone Shales, Carboniferous Limestone and 

 Millstone Grit (present in force near at hand) being entirely absent, 

 to say nothing of possibly part of the Old Eed and part of the 

 Coal-measures being likewise cut out. 



For the purposes of this investigation, and for showing the local 

 variations, a considerable number of detailed pit-sections have been 

 drawn, all to the same scale and with similar colours used for 

 similar descriptions of strata, but in this brief summary it will be 

 sufficient for explaining a few of the principal points on which 

 conjectures are hazarded, if we refer to only one or two of the 

 Somersetshire pits, and to the general typical section of the 

 Gloucestershire Coal-measures by David Williams, pp. 207 to 212, 

 vol. i. Memoirs of the Geological Survey, or Sheet 11 of the Survey's 

 Vertical Sections ; it being suggested that this general section con- 

 tains, with of course local variations, most, if not all, of the strata 

 to be found, in the Coal-measures of Somersetshire, and that the 

 equivalents of the Eadstock measures are not, as usually supposed, 

 missing in it, but to be found in a totally different position to that 

 in which we have been accustomed to look for them. 



If we take the sections of pits which are considered to have been 

 sunk through both the Eadstock and the Farrington measures, as at 

 Old Grove or Braysdown, we shall find, that if the measures beneath 

 the red shales, at those places, are correlated, as is usually done, with 

 the Gloucestershire upper series, there is plenty of room and to 

 spare on the Gloucestershire section, for the red shales, and for the 

 whole of the Eadstock group above them, but that no such seams 

 occur in Gloucestershire in the position in which, taking the Old 

 Grove or Braysdown intervals, we should expect to find them. If, 

 however, we take the section of the Farmborough sinking as re- 

 presenting the Somersetshire equivalents of the Gloucestershire upper 



