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PROCEEDINGS OE TIIE GEOLOGICAL SOCIETY. 



[Mar. 6, 



South. Yorkshire ; and it is nowhere better exposed, nor more charac- 

 teristically developed than about Pontefract *. In quarries on the 

 north and west of that town it is worked as a building-stone, being 

 of about similar coherency as the equivalent beds in the vicinity of 

 South Shields, which are likewise used by the builder. Among 

 other localities on the escarpment south of Pontefract, may be named 

 those at Carlton, Wentbridge, Hampole Stubbs, Moorhouse, Hickle- 

 ton, Barnborough Cliff, Cadeby, &c. 



§ III. Comparison of the Permian Strata of South Yorkshire with 

 those of Durham.- — Having now given some details illustrative of the 

 characters of the subdivisions of the Permian series of South York- 

 shire, it will be of interest to attempt their co-ordination with the 

 subdivisions of the equivalent series of Durham. 



Commencing at the base, we have the lower red sandstone, the 

 equivalency of which with the lower red sandstone of Durham, as 

 well as with the typical Rothliegendes of Germany, has been so long 

 known to geologists as not to require special pointing out. Indeed the 

 researches of Prof. Sedgwick clearly show the Yorkshire and Durham 

 beds to be portions of one deposit, in all probability yet continuous. 

 We have thus contemporaneous subdivisions at the base of each 

 series. If we pass on to the Brotherton beds, the highest calcareous 

 member, we find that it agrees in position with the upper limestone 

 of Durham, and, besides, that it is characterized by the same fossils, 

 and by a similar paucity of them. For these reasons I look upon 

 the Brotherton beds as the equivalent of the upper limestone, being 

 fully persuaded that such agreements could not have occurred in 

 deposits of different periods. Thus we have the lower limestone and 

 small-grained dolomite confined between two determined horizons, 

 with the marl-slate, compact limestone, and shell- and cellular lime- 

 stone of Durham as equivalents. Of these I look upon the lower 

 limestone as being parallelized by the marl-slate and compact lime- 

 stone, and the small-grained dolomite by the shell and cellular 

 limestone. The marl-slate has no special representative in York- 

 shire. And, though it is possible that its deposition may have pre- 

 ceded the commencement of that of the lower limestone, I see 

 nothing that leads me to suppose that it did. In classing it as the 

 equivalent in part to that Yorkshire member, I rely upon the fact of 

 its being the commencement of calcareous beds in the Durham series, 

 just as the lower limestone is in the series of Yorkshire, and on the 

 probability of the accumulation of arenaceous sediment having been 

 consummated and that of calcareous sediment begun about the same 

 period in both regions. It is the compact limestone, however, that 

 is to be considered as principally equivalent to the lower limestone. 

 In regarding the shell- and cellular limestone of Durham as the 

 equivalent of the small-grained dolomite, it may be objected that 

 the great difference that exists in their palseontological features is 

 opposed to such an identification. To this I would reply that the dif- 



* The fine deep soil in which the people of Pomfret grow the liquorice-root 

 to manufacture the " Pomfret Cakes," for which, among other things, their town 

 is so famous, seems to be largely composed of the debris of this member. 



