178 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



of North Wales, had led me by a process of induction, and not by 

 any "rash generalization," to adopt these views. In my Discourse of 

 1843 I used these words in reference to the last publication of Pro- 

 fessor Sedgwick himself: — "The hope, however, which was enter- 

 tained by my friend, of finding these vastly expanded lower members 

 characterized by peculiar groups of fossils has been frustrated, and, 

 whatever may be the thickness of the lowest palaeozoic division, he 

 now fully admits, that zoologically it is from top to bottom a Lower 

 Silurian Series*." 



(1845.) Having ascertained that there was a true fossiliferous base 

 in Scandinavia, Bohemia, and other countries, I then wrote (1845) 

 those earlier chapters in ' The Geology of Russia and the Ural 

 Mountains,' to which my friend makes no allusion, though in them 

 the general order from true "base-lines" was first given, from an 

 unfossiliferous bottom, through the Lower and Upper Silurian and 

 overlying palaeozoic deposits, to the Permian (then so named by 

 myself) inclusive. This was no " downward development," but an 

 original and clear exposition of a true, natural ascending order from 

 a fossiliferous base-line. 



This being done, and the North American geologists having adopted 

 the same views, it still remained a desideratum in our own country to 

 ascertain, by physical and geological proofs, if the Cambria of Sedgwick 

 was what I had suggested, i. e. essentially nothing but Lower Silurian. 



In North Wales Mr. Davis made the first approach to the ascer- 

 tainment of a base of what he termed " Silurian Rocks," by the 

 discovery (November 1845) of the now well-known Lingula-beds of 

 Tremadocf , the true physical position of which, in reference to the 

 underlying unfossiliferous grits of Barmouth and to the overlying 

 series replete with common Lower Silurian fossils, was subsequently 

 carried out by Professor Sedgwick and the Government Geological 

 surveyors. 



(1846.) In all his publications in the Proceedings and the Journal 

 of the Society, up to the early part of 1 846, Professor Sedgwick made 

 no objections to the sense which I had so prominently attached to the 

 term "Silurian" in 1841, 1842, and 1843. He had then even 

 himself so applied my nomenclature to the rocks of Cumberland 

 and Wales, that Mr. Horner, as President of the Society, after a 

 full exposition of the extension of the original Siluria, thus spoke in 

 his Anniversary Discourse of 1846 :|: : — "Since the discovery of the 

 Silurian key, he [Professor Sedgwick] has been enabled to make a 

 clear and intelligible outline of the history of these regions, which, 

 for a long time, geologists seemed to shrink from all attempts to un- 

 derstand." 



In truth. Prof. Sedgwick himself had up to that time invariably 

 appealed to my Lower Silwian as well as to my Upper Silurian 

 division and their respective fossils as his guides in elaborating the 

 fossil groups of Cumberland and Wales. How, therefore, could I, or 



* Proceed. Geol. Soc. vol. iv. p. 74 ; the same opinion was previously expressed 

 (1842) vol. iii. p. 549. 

 t Quart. Journ. Geol. Soc. vol. ii, p. 70. J Ibid. vol. ii. p. 162. 



