1852.] SEDGWICK ON THE LOWER PALEOZOIC ROCKS. 167 



much as I knew that the Silurian groups were well made out in un- 

 equivocal sections to the base of the Caradoc sandstone ; and, there- 

 fore, as far as that base descended, that the author had an apparent 

 right to claim every rock of North Wales as a member of his own 

 system. But in the published map, prepared by Mr. Warburton, 

 and not seen or revised by myself, my concessions, as above-stated, 

 are greatly mistaken and greatly misrepresented. Wlien all previous 

 doubts were cleared up in 1846, I returned, as a matter of course, 

 to my old nomenclature ; for my original sections of North Wales 

 were right, and my nomenclature was natural and true. Meanwhile 

 (and, strange as it may seem, unknown to myself, for, I believe, 

 nearly three years) my friend had extended his Silurian colours to 

 the western coasts of Wales ; and hence the origin of whatever words 

 of amicable controversy have ever passed between us. 



What I finally affirm is this, — that the whole scheme of my sec- 

 tions (from the very first which I exhibited at Oxford in 1832, and 

 at Cambridge in 1833) was physically, and (so far as my fossils went) 

 paleeontologically right — that I was never led into a false or incon- 

 gruous classification by any section of my own — that in every instance 

 in which I was led into hypotheses in any way incongruous with the 

 order of superposition indicated by my sections, I was so far led into 

 positive error — and that every instance of doubt or wavering on my 

 part arose, at the time, from a belief (I now know to have been erro- 

 neous) that the author of the * Silurian System' could not have 

 mistaken the relations of his normal lower types, but that I might, 

 perhaps, have mistaken the true relation of one or two of my highest 

 Cambrian groups. 



All doubt on this head is now at an end, and I continue to place 

 my Upper Cambrian series (a little extended, not from any change 

 of my sections, but merely as a matter of symmetrical convenience, 

 and termed the Bala group) where I placed it in 1833. The rela- 

 tions of the Bala limestone to the groups above it and below it are 

 not, in this scheme, mistaken ; nor was I ignorant of its fossils before 

 the publication of the * Silurian System,' as I have proved by pre- 

 vious quotations. 



It is true that the Llandeilo flagstone is, on this scheme, removed 

 out of the Silurian groups ; for the Llandeilo flagstone is the un- 

 doubted equivalent of the Bala limestone. It is also true that my 

 friend has published a magnificent series of fossils from the Llandeilo 

 flagstone, including therein a group he has mistaken for Caradoc 

 sandstone. But no published group of fossils entitled the author, on 

 his own canon of classification and nomenclature, to claim the Llan- 

 deilo group as his own and to give it a permanent name, until he had 

 made out its relations to the groups above it and below it ; and in this 

 last condition he entirely failed. The author has, in his great work, 

 pubhshed many admirable details respecting the development of the 

 Llandeilo groups among the Plutonic rocks of Shropshire and other 

 tracts of country on the frontiers of Wales, and for these details, and 

 the good theoretical suggestions arising out of them, he is entitled to 

 the lasting gratitude of this Society. But none of these details 



