﻿J. R. Dakyns — Prof. Hull's Carboniferous Classification. 313 



freshwater and marine : the other is the further subdivision of the 

 lower or marine portion into two by uniting the Ganister Beds, 

 Millstone Grit and Upper Limestone Shales into a Middle division, 

 and the Carboniferous Limestone and Lower Limestone Shales into 

 a Lower division. 



It is difficult to see how the Lower Coal-measures and the Mill- 

 stone Grit can properly be classed as essentially marine in the face of 

 the coal-seams and beds of Ganister, which bespeak land-surfaces : 

 but the proposal to unite the Lower Coal-measures or Ganister Beds 

 with the Millstone Grit has something to recommend it, for the 

 North of England at least, on stratigraphical grounds beyond the 

 palEeoutological ones relied on by Prof. Hull : for the two sets of 

 beds have much in common ; workable coal-seams are not unknown 

 in the Millstone Grit of Derbyshire, and such become more common 

 as we go northward : though the Sandstone Beds are as a rule coarser 

 in the Millstone Grit than in the Lower Coal-measures, yet all 

 Millstone Grits are not coarse ; some are very fine ; and grits quite 

 as coarse as ordinary Millstone Grits do occasionally occur in the 

 Lower Coal-measures. It is true we have a well-marked top to 

 the Millstone Grit in Derbyshire and Yorkshire : but this I look 

 upon as a happy accident : and were the Permian removed, where 

 it hides the upper part of the Millstone Grit, perhaps we should find 

 the Eough Kock lose its well-marked character or possibly thin 

 away altogether, and then where would our division-line be ? But, 

 what is more important, beds of Ganister, which are the distinguish- 

 ing feature of the Lower Coal-measures, occur also in the Millstone 

 Grit : this is the case as far south as Derbyshire ; and as we go north 

 the Ganister beds in the Millstone Grit become so prominent that the 

 measures containing them might easily be mistaken for the equivalents 

 of the Lower Coal-measures of South Yorkshire. 



Prof. Hull further proposes to class the Upper Limestone Shales 

 with the Millstone Grit. It has always been a difficult matter to 

 separate these two snbformations satisfactorily, except for quite 

 limited areas. The line between the two has been drawn in very- 

 different places by different observers. The late Prof. Phillips 

 drew the line below the great grit of Pendle Hill : subsequent ob- 

 servers threw the equivalent of this grit, under the name of Yoredale 

 Grit, into the Upper Limestone Shales. But Phillips was undoubt- 

 edly right in classing it with the Millstone Grit ; for the grit in 

 question is simply the basement bed of the Kinderscout Grit, from 

 which it is often quite impossible to separate it satisfactorily. The name 

 Yoredale Grit, too, is a singularly unhappy one ; for it is more than 

 doubtful whether any representative of this grit occurs in Yoredale 

 at all. But in my opinion the term Yoredale, as a synonym for the 

 old term Upper Limestone Shale, is itself incorrect. The type of 

 beds developed in the valley of the Yore is a very marked one ; also 

 very peculiar, by no means generally characterizing the beds below 

 the Millstone Grit ; it would seem better therefore to retain the old 

 term Upper Limestone Shales for these measures generally, reserving 

 the term Yoredale series for those cases in which the beds approxi- 



