164 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Feb. 25, 



the author then thought the evidence of sections necessary to his 

 "System," and that it did not necessarily include every group 

 with Silurian fossils. At that time the important point between 

 us was to determine the limits of our respective sections. He 

 afterwards shifted his ground of classification altogether, but on 

 principles not communicated to myself; and ended by demanding 

 from me a proof that my Cambrian series contained a group of 

 fossils entirely distinct from those of his lower Silurian rocks. He 

 required of me what I had shown him to be impossible before his 

 System had a name. As to the palseontological relations of the Cam- 

 brian groups, my views, though expanded during the progress of dis- 

 covery, never underwent any fundamental change. This progress 

 did, however, prove that the word system was, from the first, applied 

 by the author incorrectly to his "Silurian" groups. I worked up- 

 wards through the whole Cambrian and Silurian series : my friend 

 worked downwards into the upper part of the Cambrian series, and 

 there came to a fault. There was an undoubted overlap in our 

 ascending and descending sections, producing no small confusion, but 

 this confusion was simply caused by his own mistakes and not by 

 mine : yet is this confusion, on the scheme of my friend, to end by 

 subordinating Cambria to Siluria — by a system of grouping, in the 

 upper part of which the spirit of subdivision is carried, perhaps, to 

 excess, while in the lower part all subdivision, based on good sec- 

 tional evidence, is discarded — by making more than 20,000 feet of 

 strata the equivalents of one ** Silurian" group ! No power on earth 

 can stereotype and perpetuate a nomenclature so utterly incongruous, 

 — one part simply geographical and sectional, — the other part neither 

 geographical nor sectional ; but evolved through a downward develop- 

 ment which is out of nature, and strikes at the root of every prin- 

 ciple of philosophical arrangement. We may, no doubt, analyse the 

 successive deposits of a new country in the descending order, and this 

 may sometimes be the very best method. But when we proceed to 

 systematize the deposits and give them names, we are absolutely 

 compelled to reverse the process j otherwise we build without a foun- 

 dation, and violate the historical development of nature. 



My friend and opponent tells me {loc. cit. p. 173), that, before Ms 

 Silurian System was fixed, foreign geologists had applied the term 

 "greywacke" indiscriminately to the Devonian and other palaeozoic 

 groups. This is very true. The upper Silurian groups were fixed on 

 right principles, and this was a very great boon to geology, and soon 

 led, almost by a philosophical necessity, to the fixation of the Devo- 

 nian series. But the lower Silurian groups were not fixed by the 

 author. His nomenclature was premature, and his base-line was sec- 

 tionally wrong ; and, so far from leading to discovery, it retarded the 

 progress of palaeozoic geology for, I believe, not less than ten or 

 twelve years. 



I accept at once the canon, " that a good nomenclature can only 

 be based on a conformity of successive and similar organic remains *." 

 For we all admit that a good geological nomenclature is, not simply 

 * Loc. cit. p. 173. 



