﻿310 Rev. A. Irving — On the "Permian" and " Neiv Red." 



the Geological Survey upon the district. The more the matter was 

 studied, the moi'e did I lose confidence in the dictum above referred 

 to, and I could not help coming finally to the conclusion, as Prof. 

 PhillijDS had done, with reference to the same two series of rocks 

 in another area, that '' their physical history was upon the whole 

 one great series of natural operations." Nor had I overlooked, 

 as Mr. Aveline' seems to imagine, the few and meagre data which 

 were furnished by him and by Prof. Hull in their respective 

 " Memoirs," from which their conclusions as to the great uncon- 

 formity between Bunter and Permian was drawn. It is not for me 

 to point out to Mr. Aveline, or to any other geologist so practised 

 and experienced in field-work as he is, that we have here a question 

 where we must decide, if at all, by the balancing of probabilities. 

 The direct evidence of any great unconformity is very weak 

 indeed. The intercalation of the middle marls and sandstones by 

 "Worksop and northward furnishes very little proof of the removal 

 by post-Permian denudation of the Upper Magnesian Limestone as 

 we proceed south ; as I think any one will see who will take the 

 trouble to weigh well the reasoning of Mr. E. Wilson, F.G.S., in the 

 May Number of this Magazine (p. 238). I must say that I agree with 

 this gentleman entirely as to the true intei^pretation of the facts 

 reiterated with so much emphasis by Mr. Aveline in his recent 

 communication to this periodical : facts which both Mr. Wilson and 

 myself were fully conversant with, since they were stated years ago 

 in the " Memoirs." And not only are we now in a better position 

 to judge of their true bearing, on account of the great accession to 

 OTir stock of data which has been furnished by the recent develop- 

 ment of the South Notts Coal-field ; but I venture to say that any 

 one who had seen the great intercalated masses of dolomitic 

 sandstone which are quarried in the neighbourhood of Mansfield, 

 might well feel sceptical (in the absence of pateontological evidence) 

 as to the precise identity of a particular member of the Magnesian 

 Limestone group at Worksoj), with the beds that occur between 

 Mansfield and Nottingham ; where the lateral variation of the whole 

 series is so great, and the genei'al tendency of even the dolomite 

 itself to become more and more coarse-grained, flaggy, and gritty in 

 its i^rogress southward, is most pronounced. Nor do I forget (even 

 with the circumscribed geological vision of a "local geologist") that 

 this is in general harmony with the thinning-out of the whole series 

 of the Magnesian Limestone from a thickness of 600 feet in the 

 county of Durham, to that of a few flaggy bands in Nottinghamshire. 

 Every one who has done any field-work at all, must know how 

 hazardous it is to generalize in a spirit approaching to anything like 

 dogmatism, on the actual relation of two sets of rocks, both of which 

 are unfossiliferous, unless they had been traced continuously across 

 the country; and this Mr. Aveline, with the small amount of data 

 afforded, will scarcely maintain to have been done in the present 

 instance. That a southern and south-western boundary must have 



' See Mr. Aveliiie's article in the April No. of Geol. Mag., p. 155, " On the 

 Magnesian Limestone and the New Eed Sandstone of Nottingham." 



