258 Dr. Wheelton Hind — Zones of the Carboniferous. 



that any Carboniferous rocks exhibit such a persistence of conditions 

 of deposit as the Carboniferous Limestone of Derbyshire; for the 

 majority of the Carboniferous beds north of the Midlands, and in 

 Scotland, exhibit, rather, characters indicative of successive changes. 

 If the thick deposits of Carboniferous Limestone typical of North 

 Staffordshire, Derbyshire, and South Yorkshire be traced north, 

 it appears in the north of Yorkshire to be broken up into different, 

 well-recognized beds, separated by beds of shale of varying 

 thickness, the latter thinning out towards the south. The upper 

 beds (Yoredale) in this district (Ingleborough) contain several beds 

 of limestone, separated by shales, which do not occur in the same 

 series further south. Moreover, many fossils are common to these 

 limestones, and to the " Massif" further south. 



Viewing the Carboniferous rocks of Great Britain as a whole, 

 nothing is clearer than the fact that they do not for the most part 

 fall in with the fourfold classification — 



Coal-measures, 

 Millstone Grit, 

 Yoredale Beds, 

 Carboniferous Limestone — 



of the textbooks. Such a classification will only be found suitable 

 in the field in the North Midlands, and I believe that a twofold 

 division as is made in North America would better represent the 

 British Carboniferous strata. 



Upper Carboniferous ^ Coal-measures. 



or Antbraxiferous 

 division 



Millstone Grit series. 



> 



(Carboniferous 

 Limestone 

 series, 

 series. 



In this scheme it is not intended for a moment to make out that 

 the two divisions of the Lower Carboniferous in England are the 

 equivalents of those in Scotland, or to use the word equivalent in 

 any other sense than that in Scotland certain beds are at the base 

 of the series, whilst in England others are in this position. It 

 would appear that in Scotland, Ireland, and the South of England, 

 the Carboniferous period came in gradually, without any very 

 marked change from pre-existing conditions, so much so that there 

 has been much discussion as to the precise position where the line 

 between Carboniferous and Upper Devonian beds should be drawn. 



In Yorkshire, where alone in the Midlands the base of the 

 Carboniferous Limestone is exposed, there are only a few feet of 

 impersistent calcareous conglomerate between it and unconformable 

 Silurian rocks. In this area marine conditions seem to have com- 

 menced suddenly, and the period of marine encroachment which 

 would have given rise to littoral sediments, to have been of too short 

 a duration to give rise to any deposit. 



The majority of the limestone deposits of Carboniferous age are 



