160 PROCEEDINGS OP THE GEOLOGICAL SOCIETY. [Feb. 25, 



Cambrian System and lower Cambrian System, in conformity with a 

 language in common nse — to designate two great collective groups of 

 Cambrian rocks ; but I always used these terms in a geographical and 

 geological, and never in any strictly paleeontological sense : and that 

 these two collective groups were injPerior to all the Silurian rocks I 

 assumed on what I thought an irrefragable authority — that of the 

 author of the * Silurian System.' That the author's views respecting 

 the meaning of his word '' System " were at first nearly the same 

 with my own, I am morally certain ; otherwise he could not, on the 

 evidence of sections which we examined together, have excluded the 

 Bala limestone from his lower Silurian groups. Had he identified 

 the Bala limestone with his Llandeilo flag, he must inevitably have 

 admitted that his base-line in South Wales was entirely erroneous ; 

 but in 1834 (and afterwards in 1839) he was prepared to make no 

 such admission. The strange, and, I may venture to say, the unna- 

 tural, hypothesis, that a single group — the Llandeilo flag — might be 

 developed downward through all lower Cambrian groups, and that 

 every rock with the (so-called) lower Silurian fossils (no matter what 

 its place in the great Cambrian series) might "be included in the 

 Lower Silurian group*," was therefore, as I have stated before, an 

 after-thought ; which never could, I believe, have arisen in his mind, 

 had he not discovered that his own base-line was not merely ill- 

 defined, but founded on a positive misinterpretation. 



When, in 1842 and 1843, I had the pleasure of traversing thefos- 

 siliferous parts of North Wales with Mr. Salter, I had no expecta- 

 tion whatsoever of finding many fossils specifically or generically dif- 

 ferent from those which had been delineated by Dalman, Murchison, 

 and other authors who had described the older fossil types. After 

 the Devonian fossils (for many years the opprobrium of the lower 

 palaeozoic series) were removed to their proper place in the palaeozoic 

 system, there was no longer the shadow of a difficulty in defining the 

 leading palseontological characters of the lower palaeozoic rocks. The 

 real and only difficulty was in defining the number and sectional place 

 t)f their subordinate groups. Their upper groups had been admirably 

 determined in the " Silurian System." But their lower groups were, in 

 that system, either not defined at all, or defined by a reference to local 

 sections which have been proved erroneous. My only hope (in 1 842- 

 1843) was — that, through the able assistance of my friend Mr. Salter, 

 I might establish, in the field, a series of fossil groups that would en- 

 able me to split up the great Bala and lower Cambrian series into 

 separate stages resembling those of the true " Silurian System." In 

 this attempt we failed. But this failure did by no means prove that 

 there was not a great Cambrian series below the defined groups of 

 Siluria. It did, however, prove — what had often been urged before 

 — that the word system, as applied palceontologically to the collective 

 groups of Siluria, had been not merely premature, but erroneous. 



Should any one ask, what matters it by what name the Welsh series 

 of rocks may be called, so long as we define the meaning of our terms ? 

 I should at once reply that good names are of great consequence. That 



* Quart. Journ. Geol. Soc. 1847, vol.iii. p. 170. 



