126 D. C. Davies—The Millstone Grit of North Wales. 



had made together near Owestry, " Your so-called Millstone Grit 

 much perplexes me." It may not be amiss, therefore, in a few con- 

 cluding remarks, to consider more fully this question. 



The reasons urged for comprising the greater portion of the Mill- 

 stone Grit of North Wales with the Yoredale series are, as I under- 

 stand them, as follows : — 1. The presence of Carboniferous Limestone 

 fossils ; 2, the supposed greater resemblance of the Sandstones to the 

 Yoredale rocks than to the Millstone Grit elsewhere ; and 3, the 

 intercalation of limestones with the sandstone beds. With regard to 

 the first, it will be sufficient to repeat what I have already said, that 

 we find the same fossils extending upwards through the Millstone 

 Grit of the north, only as yet confined to the calcareous beds and 

 shales ; and further that we find these same fossils within a yard of 

 the Coal Measures in that uppermost and most persistent member of 

 the North Wales Grits, whose equivalency with the Millstone Grit 

 is allowed by all. Secondly : it must be admitted that the sections 

 of the Yoredale and Grit beds, taken from the Northern and Midland 

 Counties, show great variations and gradations in the texture of the 

 sandstones. Thus Professor Phillips writes : ^ " Now of all the. 

 strata of the Yoredale series, the limestones are by far the most 

 continuous and permanent : had we attempted to construct the diagram 

 of corresponding geological age, in distant parts of Yorkshire, by a 

 comparison of the sandstones and slates, the results would have been 

 most imaginary, and lines of demarcation in the Carboniferous 

 series would have been worse than useless." By a comparison of the 

 sections given in. this paper with those given by the various authors 

 who have described similar rocks elsewhere, it will, I think, be seen 

 that, while the supposed Millstone Grit of North Wales will compare 

 at various horizons for crystallization and pebbly grits with those of 

 the north, these in their turn present us with shales and finer sand- 

 stones, similar to those of the Welsh Border. 



Nor, thirdly, can the presence of the limestone in the middle 

 portion of these beds be held as deciding the matter, because, in all 

 the sections of the Millstone Grit, given by Professor Phillips, in his 

 " Geology of Yorkshire," there are bands of limestone : indeed, there 

 was an attempt once made I believe on this account to sweep the whole 

 of Grits, etc., lying above what was known as the Hadrow limestone, 

 including the Ingieborough Grits, into the Yoredale series. Pro- 

 fessor Phillips having to contend, that it would be absurd to absorb 

 a formation, whose distinctive characteristic was sandstone, into one 

 whose distinctive characteristic was limestone, because of the 

 occurrence of a few feet of the latter in the midst of the former. 

 The same remark holds good of the North Wales sections, excepting 

 that at Mold, and here I must confess the analogy ceases. Indeed, 

 when I first saw this section, and saw the pale sandstones at the top 

 pass downwards through purply calcareous sandstones into un- 

 doubted limestones, abounding in encrinital stems, as at all the other 

 points of junction between the two formations, I was led to accept 

 Mr. Green's suggestion, in the paper referred to, "that all the lower 

 1 " Geology of Yorkshire," vol. ii. 



