1852.] SEDGWICK ON THE LOWER PALiEOZOIC ROCKS. 159 



When this mistake (for years the only stumbling-block in the way of 

 a good arrangement of the lower palaeozoic groups) was removed, the 

 author made no new adjustment of his Silurian nomenclature, but pro- 

 ceeded to develope his Llandeilo group — upwards through more than 

 3000 feet, and downwards through more than 20,000 feet — until at 

 length his Silurian System was spread over all Cambria. Where do 

 we find any proceeding like this among the generalizations of Dr- 

 Smith ? My friend and antagonist utterly deserted the principles of 

 Smith, by virtually discarding the force of sectional evidence, and by 

 endeavouring to establish his nomenclature on the mere evidence of 

 fossils ; and by then proceeding (through what was called a downward 

 development of the Llandeilo flagstone) to involve all the lower rocks 

 of Wales under his lowest Silurian group ; although that group was 

 avowedly misplaced and misinterpreted within the comparatively nar- 

 row limits of his published sections. Anything in more direct antago- 

 nism to Smith's sober inductive habits and scheme of nomenclature 

 could hardly be expressed in language : and this was done while the 

 author was aware that another name (and, I aifirm, the right name on 

 the principles of Smith) had been given to that vast and most difficult 

 series of Cambrian rocks which he had not personally examined, yet 

 which he was thus identifjdng — by a downward and unnatural process 

 of development — with his lowest Silurian group. Nor was this done 

 at all after any assumed right of a second conquest ; for, on his part, 

 it was a development of the closet and not of the field. 



The author of the ' Silurian System ' has informed the Society, in 

 a former controversial paper*, that he himself suggested a name 

 (Snowdonian) for the great series of Cambrian rocks ; and from 

 thence he seems to argue that he has a right to change the name. 

 But he did not then know, what was well-known to myself, that the 

 term Snowdonian was quite inapplicable, and that the position of the 

 crest of Snowdon in the general section was doubtful ; inasmuch as 

 it merely formed one trough among the undulations of North Wales, 

 between the two, above-mentioned, base-lines of the lower Cambrian se- 

 ries. I readily adopted the good geographical term Cambrian to desig- 

 nate the most noble and difficult sequence of rocks within the limits 

 of England and Wales f ; but at the same time I strenuously objected 

 to the word system (both on geological and palseontological grounds), 

 whether applied to the collective Silurian or Cambrian rocks. This 

 Society heard these objections urged by myself (and I may add by others 

 — especially by Professor Phillips) again and again. I objected to the 

 word system^ as too definite for our state of knowledge, and I always 

 affirmed that the Silurian System was without any good palseonto- 

 logical base. 



Since the year 1835 I have repeatedly used the words upper 



in which the Llandeilo and Caradoc groups are placed in an entirely false posi- 

 tion (Quart. Journ. Geol. Soc. Jan. 6, 1847, vol. iii. p. 167). Surely (and quite 

 inde[)endently of any question of priority) a nomenclature constructed upon such an 

 erroneous base cannot he considered final, but requires revision and correction. 



* Quart. Journ. Geol. Soc. 1847, vol. iii. p. 167. 



t I the more readily adopted the word Cambrian because it was a very slight 

 change from the word Cumbrian, by which I had long been in the habit of desig- 

 nating the corresponding part of the palaeozoic series in the north of England. 



