Frof. T. Sterry Hunt — On Cambrian and Silurian. 389 



the Lower Silurian system." This was again insisted upon by him 

 in 1888 and 1841. (Proc. Geol. Soc. vol. ii. p. 679 ; vol. iii. p. 548.) 

 It was not until 1840 that Bowman announced the same conclusion, 

 which was reiterated by Sharpe in 1842. (Eamsay, Mem. Geol. 

 Surv. vol. iii. part 2, p. 6.) 



In 1839 Murchison published his Silurian System, dedicated to 

 Sedgwick, — a magnificent work in two volumes quarto, with a 

 separate map, numerous sections and figures of fossils. The succes- 

 sion of the Silurian rocks, as there given, was precisely that already 

 set forth by the author in 1834, and again in 1835 ; being, in de- 

 scending order, Ludlow and Wenlock, constituting the Upper 

 Silurian, and Caradoc and Llandeilo (including the Lower Llandeilo 

 beds or Stiper-stones), the Lower Silurian. These are underlaid by 

 the Cambrian rocks, into which the Llandeilo was said to offer a 

 transition marked by beds of passage. Murchison, in fact, declared 

 that it was impossible to draw any line of separation either litho- 

 logical, zoological, or stratigraphical between the base of the Silurian 

 beds (Llandeilo) and the upper portion of the Cambrian, — the whole 

 forming, according to him, in Caermarthenshire, one continuous and 

 conformable series from the Cambrian to the Ludlow. (Silurian 

 System, pages 256, 358.) By Cambrian in this connexion we are 

 to understand only the Upper Cambrian or Bala group of Sedgwick, 

 as appears from the express statement of Murchison, who alludes to 

 the Cambrian of Sedgwick as including all the older slaty rocks of 

 Wales, and as divided into three groups, but proceeds to say that in 

 his present work (the Silurian System) he shall notice only the 

 highest of these three. 



Since January, 1834, when Murchison first announced the strati- 

 graphical relations of the lower division of what he afterwards called 

 the Silurian system, the aspect of the case had materially changed. 

 This division was no longer underlaid, both to the east in Shropshire 

 and to the west in Wales, by a great unfossiliferous series. His 

 observations in the vicinity of the Berwyn hills with Sedgwick in 

 1834, and the subsequently published statements of the latter, had 

 shown that this supposed older series was not without fossils ; but 

 on the contrary, in N orth Wales at least, held a fauna identical with, 

 that characterizing the Lower Silurian. Hence the assertion of 

 Murchison, in his Silurian System, in 1839, that it was not j)0ssible to 

 draw any line of demarcation between them. The position was very 

 embarrassing to the author of the Silurian System, and, for the 

 moment, not less so to the discoverer of the Upper Cambrian series. 

 Meanwhile, the latter, as we have seen in 1842, re-examined with 

 Salter his Upper Cambrian sections in North Wales, and satisfied 

 himself of the correctness, both structurally and palseontologically, 

 of his former determinations, Murchison, in his anniversary address 

 as President of the Geological Society in 1842, after recounting, as 

 we have already done, the history of the naming by Sedgwick in 

 1835 of the Cambrian series, which Murchison supposed to underlie 

 his Silurian system, proceeded as follows : " Nothing precise was 

 then known of the organic contents of this lower or Cambrian 

 system except that some of the fossils contained in its upper members 



