456 



The Known Coal Field. 

 I propose in the first iustaiice to treat the geographical position 

 of the Carboniferous formation in Somersetshire in its more limited 

 sense by confining your attention to the knotvn coalfield of this 

 district ; and I would at the outset recall to your recollection the 

 different subdivisions of which it is composed as seen most clearly 

 in the section* from Chewton Mendip to Southstoke, near Bath, now 

 exhibited. You will observe that the upper part of the section is 

 occupied by the secondary rocks, beginning at the Bath end with 

 the Great oolite, and in proceeding westward descending through 

 the Fullers' earth rock, Fullers' earth, the Inferior oolite, the Lias, 

 and the Keuper marls, to the Conglomerate beds of the Trias, which 

 form the base of the secondary rocks in this district. You will also 

 observe that the lower part of the section consists of the Old red 

 sandstone, which is extensively exposed in the anticlinal ridge of the 

 Mendip Hills. Between these limits lie the Carboniferous strata 

 which consist in descending order of — 



1. The Radstock series ) 



2. The Farrington ditto | forming the upper division. 



3. The Pennant sandstones. 



4. The lower division of productive Coal measures, consisting 



of the New Rock and Vobster groups. 

 6. The Millstone grit or farewell rock, and 

 6. The Carbo7iiferous limestone with its associated shales. 

 The probable limits of each of these sub-divisions, and especially 

 of the upper four, which are of the greatest commeicial importance, 

 I propose this evening to investigate ; describing first of all those 

 areas which are exposed on the surface, and afterwards endeavouring 

 to define the range of each sub-division beneath the secondary rocks. 

 Outcrops of Old Red Sandstone. 

 It is obvious that the extent of the Carbonijerous rocks must be 

 very much affected by the position of the Old red sandstone, the 

 foundation rock on which they rest. 



The Old red is seen at various points on the west, north and 

 south of the Somersetshire and Gloucestershire basin. On the 

 south it forms the backbone of the entire Mendip range, extending 



* A section prepared for the Royal Coal Commission, and not yet 

 published. — Ed. 



