184 PKOCEEDINGS OE THE GEOLOGICAL SOCIETY. [Peb. 10, 



fields round the margin of the Triassic plain of Cheshire, and the 

 extension of the Coal-measures below the Triassic and Permian 

 rocks of the plain. The position of the axis of Lower Carboni- 

 ferous rocks from west to east is represented by the unshaded band 

 ranging under the banded portion (representing the Trias and Per- 

 mian area), and emerging at each side in the tract now formed of 

 Lower Carboniferous beds in N^orth Wales and East Cheshire. The 

 shaded portion banded with close lines shows the extent of the Coal- 

 measures to the north and south of the axis covered by Permian 

 and Triassic formations ; and it will be observed that the whole Coal- 

 tract, both at the surface and concealed, resolves itself into two great 

 coal-fields to the north and to the south of the supposed barrier of 

 Lower Carboniferous rocks, that to the north being continuous with 

 the Coal-fields of Flintshire, Lancashire, and Cheshire, that to the 

 south with the Coal-fields of Denbighshire and North Staff'ordshire. 

 A southerly prolongation of this tract probably connects it with the 

 Shrewsbury Coal-field. 



It will be observed that at the northern part of the map, and ex- 

 tending inland for some distance from the coast of Lancashire, there 

 is a large banded tract of ground covered by Triassic rocks, under 

 which, if penetrated, I consider that only the Lower Carboniferous 

 beds (below the coal) would be found, the whole of the Coal-measures 

 having been removed by denudation before the Permian period. To 

 this tract I have referred in my paper on the relative ages of the 

 physical features and lines of elevation of Lancashire (Quart. Journ. 

 Geol. Soc. vol. xxiv. p. 333). 



Discussion. 



Prof. Ramsay considered that the lithological differences in the 

 Permian rocks of the two areas referred to were hardly so great as 

 was supposed by Mr. Hull. 



Mr. Peestwich remarked that the nearly equal thickness of the 

 Permian deposits in the two areas was in favour of their having 

 been deposited in continuity. 



Mr. W. W. Smyth considered that the difference between the 

 Permian beds in question was not so great as the author supposed, 

 but that the undoubted existence south of Chester of a breadth of 

 5 or 6 miles of Bunter Sandstone lying immediately upon the Mill- 

 stone Grit, although observed only at one point, was strongly in 

 favour of the author's hypothesis. 



Mr. Hull stated in reply that the difference between the two 

 groups of Permian rocks to which he had referred was so great as to 

 render their identity at first sight very doubtful. The extent of the 

 anticlinal at Rushton Spencer is so great that it must be inferred to 

 have extended far both to the east and west. 



