164 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



in proof of which I need only appeal to the preceding pages of this 

 paper. 



A nomenclature to be good should admit of a general applica- 

 tion, and at the same time it ought to disturb as little as possible 

 any previously accepted natural arrangement. The rocks of the 

 Cumbrian cluster of mountains admit of three great collective groups 

 or systems: — 1. Skiddaw slate. 2. Green roofing-slate and por- 

 phyry. 3. Fossiliferous slate and flagstone. These three subdivi- 

 sions were established about thirty years since by Mr. J. Otley. 

 The third collective group might very properly have been called 

 the Westmoreland system ; and, as above stated, it is the exact 

 equivalent of the Silurian system. Should fossils be ever found in 

 the two lower groups (which fill the exact place of the older Cam- 

 brian rocks), there can be no doubt that they would in general spe- 

 cifically agree with the fossils of the lower groups of North Wales, 

 and that several of the species, and probably the greater number of 

 them, would also be identical with those of the Coniston limestone. 

 This might be a good reason for packing the Coniston limestone in 

 the middle Cumbrian group, but could be no reason for describing, 

 the great Cumbrian mountains under the name of the Westmore:, 

 land system. Such language would not merely be incongruous, but ^ 

 would tend to undermine all previous arrangements, and to throw^" 

 the geology of this part of England into inextricable confusion. Yet 

 this incongruity would be exactly of the same order with that 

 which is introduced, in defiance of natural sections, natural deve- 

 lopment, and the geographical propriety of language, by classing 

 all the older Cambrian rocks under the Silurian system. 



After the distribution of the principal organic groups has been 

 settled (and it can only be settled by the previous determination of 

 the physical groups), we might easily adopt a congruous nomen- 

 clature founded only on palasontological characters. In that case 

 our geographical names ought to disappear from the designation of 

 the successive epochs. But even then we should be compelled, in 

 all local descriptions, to enumerate the successive collective groups 

 (such as Cambrian, Silurian, Carboniferous, &c.), and give them 

 some appropriate name. Geology is not however yet ripe for a 

 mere palaeontological nomenclature. Taking it as an advancing 

 science, I think the principles of nomenclature hitherto adopted are 

 best fitted to its condition. 



In conclusion, and by way of summary to all that has been stated in ^ 

 this paper, I venture to affirm, that the innovation in the nomencla-/ 

 ture of our older British palaeozoic groups (against which I have ' 

 been contending) is not merely based in error and misconception,^ 

 but also that it involves a change of principle and a very great in- 

 congruity of language. I continue therefore the old nomenclature, 

 because more congruous, more natural, and more strictly in ac- 

 cordance with physical and zoological development. 



