1852.] SEDGWICK ON THE LOWER PALEOZOIC ROCKS. 157 



and, would it not have been wiser and better to retire one step, and 

 to expunge the Llandeilo group from the Silurian rocks, and to base 

 the system on the Caradoc sandstone of the unambiguous sections ? 

 Had that step been taken, the Silurian groups would at once have 

 taken their right and undisputed place ; and there would have been 

 nothing to stand in the way of the true arrangement of the whole 

 Cambrian series, so far as it isl known*. Such a change would 

 only have sacrificed one single group, the relations of which, as we 

 now know, had most certainly been misunderstood by the author of 

 the * Silurian System' ; but instead of this, he shifted his own base- 

 line to the base of the whole Cambrian series f. Thus the name I 

 had given to the Cambrian series, in the elaboration of which I had 

 made no mistake, was to be sponged out ; and the series was to re- 

 ceive a new name that was utterly inappropriate. * 

 Our whole scheme of nomenclature of the lower Palaeozoic rocks is 

 geographical. This scheme was followed out, from first to last, in 

 the " Silurian System." The system, and all the subordinate groups, 

 were defined by geographical names. Now it is surely an axiom in 

 geological nomenclature, that if we give a new geographical name to 

 any group of strata, that name must refer us to a spot near which we 

 find the group well-developed. In Cambria the whole series of the 

 oldest palaeozoic division is more nobly developed than in any other 

 part of Britain (on this point I can speak from my own experience) ; 

 while in Siluria we find only the highest group of the whole series. 

 This would have been a sufficient reason for changing the name Silu- 

 rian into Cambrian, had, by any caprice or accident, the name Silurian 

 been first given to the older Cambrian rocks ; but it seems to me a 

 very strange reason for changing the name Cambrian (a right name 

 for a great series of rocks well-developed in Cambria, and a name which 

 had the undoubted priority) into Silurian. If indeed we had a good 

 and perfect series of the older palaeozoic groups in Siluria, then the 

 words " Silurian System" might be stereotyped as a general desig- 

 nation of all the lower palaeozoic rocks of Britain. But Siluria shows 

 us no such typical series, while Cambria does. On the ground, 

 therefore, of geographical propriety, as well as of priority, I vindicate 

 the claims of the Cambrian series for a place in our nomenclature. 



* The section from the Menai, over the Berwyns, and to the coast of Shrop- 

 shire, as explained to the British Association in 1833, differed in no essential re- 

 spect from the ideal section of the Cambrian series given above in the Tabular 

 View. At the same time I identified (provisionally) the coarse grits near the line 

 of the Holyhead road (Cernioge, Modwl Eithen, &c.) with my friend's shelly sand- 

 stone (Caradoc) : and as for the Denbigh flagstone, there never was, from the first, 

 any doubt of its identity with the Silurian flags of Welsh Pool and the Long Moun- 

 tain. My section, therefore, through the whole series (Cambrian and Silurian), 

 was in 1832, excepting in small details, nearly as good as it is now; but the iden- 

 tification (in 1834) of the Meifod beds, by my friend, with his typical Caradoc 

 sandstone, threw the general section into confusion, and destroyed the true key- 

 stone that held the Cambrian and Silurian portions together. 



t It has been said (but never by Sir R. 1. Murchison) that I was a consenting 

 party to this change. The statement is contrary to fact. The change took place 

 (I believe in 1843) two or three years before I was acquainted with it. Had it been 

 known to me at the time, I should probably have entered a public protest against it. 



