436 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [May 22, 



The strongest fact on behalf of the lower character of the hmestone, 

 is doubtless that on one side it is in absolute contact with the Caradoc 

 sandstone, and on the other is separated from the grit by only a few 

 feet of shale. Notwithstanding this, however, I am led to retain my 

 opinion that the Xash hmestone is identical with that of Wenlock 

 rather than Woolhope. 



1 . TMiile the hmestone strata of Woolhope and elsewhere are for 

 the most part impure and only burnt when better cannot be obtained, 

 that at Xash Scar is remarkably pure and highly crvstalhne. The 

 mineralogical character of the Woolhope limestone given bv Sir 

 Roderick Murchison is this : " a hard, dark-blue, thick, flag-hke 

 Hmestone ; the surfaces frequently chequered with transverse septa, 

 occupied by pink calcareous spar." Not one of these terms is apph- 

 cable to the formation at Xash. The yet more impui-e limestone 

 occurring in the sandstone of the river Onney section, in Shrop- 

 shire, and which beds, it is well to remember, are placed by Sir 

 Roderick Mm'chison as forming the top of the Caradoc beds, not 

 only on account of their position and organic remains, but also by 

 reason of their mineral structure, could never be mistaken for that 

 of Xash ; and yet this is a fair comparison to make, for the beds 

 of grit and sandstone of Caen Wood are the prolongation of the 

 Caradoc district connected by the before-mentioned grit of Brampton 

 Brian. 



2. There is no passage from the sand and grits into the Nash 

 hmestone. In walking over Xash Scar, the hmit of the sandstone 

 wherever the surface is bared to the rock may be defined to an iuch, 

 and neither above nor below that boundary is there any trace of the 

 sandstone on the one hand or of the hmestone on the other. So 

 on the north side of the hill, there is no interlacing of the shale 

 with the grit, the escai-pment of which presents a clear and decided 

 face. 



3. The Wenlock rocks fr'om the point of their expansion in the 

 Wigmore valley on their strike south-west towards Builth, are consi- 

 derably contracted, and at Kinsham, about four miles north-east of 

 X'ash, merely occupy the gorge of the river Lug. At Xash, as already 

 shown, the development of the shale is only sufiicient to identify it, 

 and it can scarcely be traced in the dislocated coimtry of Old Radnor. 

 Regarding then the hmestone and shale as one formation, and bearing 

 in mind the causes which produced in a former sea-bottom a calca- 

 reous rather than an argillaceous deposit, the fact that the hmestone 

 instead of the shale is at one spot brought into contact with the in- 

 ferior nucleus of sandstone, cannot be a ground for refusing to regard 

 the hmestone as the equivalent of that of AYenlock. 



The inference to be derived from an examination and comparison 

 of the fossil contents of the limestone, remains to be considered. 

 With reference to this branch of the question it may be premised, that 

 there cannot be any question as to the age of the formations superior 

 and inferior to the limestone and shale. The sandstone of Caen 

 W^ood contains the characteristic fossils of the Caradoc, including an 

 abundance of the Fentamerus ohlongus. Sow., Atrypa hemisphcBrica, 



