1852.] SEDGWICK ON THE LOWER PALEOZOIC ROCKS. 155 



papers. I used the word Frotozoic to prevent any wrangling about 

 the words Cambrian and Silurian. I gave one colour to the whole 

 Protozoic series, only because I did not knov/ how to draw a clear 

 continuous line upon the map between the upper Protozoic (or lower 

 Silurian) rocks and the lower Protozoic (or lower Cambrian) rocks. 

 This was stated to the Society when my papers were read ; nor did I 

 ever dream of an incorporation of all the lower Cambrian rocks in the 

 system of Siluria. Yet as I discovered (to my no small astonishment), 

 for the first time during the past week, he has, in an explanation of 

 the Protozoic, and colourless, portion of the map, written *' Lower 

 Silurian (Protozoic)," thereby stultifying my whole paper, the very 

 gist and object of which was to show that there was a great series of 

 groups — lower Protozoic (or lower Cambrian) — below the lowest 

 rocks of the "Silurian System*." 



After the erroneous identification of the Upper Bala and Caradoc 

 groups in 1843 (to which I was driven by the identification, above 

 mentioned, of the Meifod and Caradoc groups), I believed that many 

 of the South Welsh undulating slate-rocks would prove to be upper 

 Silurian. I put the hypothesis to the test in several traverses through 

 South Wales, made along with my friend John Ruthven in 1846. In 

 this country, which I had never visited since 1834, we found fossils 

 on every line of traverse, and all of them were of the, so called, lower 

 Silurian types. It was plain, therefore, that the Bala limestone was 

 not Caradoc ; and thence it also followed, that the Meifod beds did 

 not belong to the Caradoc group, but to that of Bala. It then 

 became obvious, to demonstration, that in the extension of the Silu- 

 rian system towards the south-west, beyond the limits of the typical 

 Silurian country, the author of the " System " had made a double 

 mistake, — first, in identifying certain shelly beds of his Llandeilo 

 group with the Caradoc sandstone ; and secondly, in placing the 

 same group stratigraphically above the undulating beds I had (I think, 

 very properly) called Upper Cambrian. 



This comment would have been uncalled for, had he not made his 

 own mistake a part of the ground for sweeping out all the Cambrian 

 groups from North Wales. I repeat, emphatically, that before 1834 



* The map (Proc. Geol. Soc. vol. iv. p. 268) is a mere sketch, which pretty 

 well represents my conceptions of the structm-e of North Wales in 1843. But it 

 contains some grave errors, which I could have corrected at the first glance : e. g. 

 a range of Bala Hmestone northwards from Llanwddin is properly laid down ; but 

 a second band of the same limestone farther to the east (which unites with the 

 former to the south of Llanwddin, in a district where all the beds are inverted) is 

 unfortunately omittgd, although it was plainly traced and coloured on my field- 

 map. I suspect that, in the explanation of the blank portion of the rough map 

 exhibited in illustration of my paper, I had written Lower Silurian and Protozoic, 

 and that Mr. Warburton, erroneously conceiving the two terms identical, changed 

 the words into Lower Silurian {Protozoic). Had the published map been allowed 

 to pass, in its present form, after a revision by myself, I should virtually have sur- 

 rendered the whole question now in debate, I do not by any means accuse Mr. 

 Warburton of any intentional injustice— quite the contrary : for I know that he 

 gave his best efforts to the abstract. But he had undertaken a task for which he 

 was not prepared, inasmuch as he had never well studied any series of rocks like 

 those described in my papers. 



