Palaeozoic Geology. 54-9 



adopted the name of Cambrian. Nothing precise was known at 

 that time of the organic contents of this lower or Cambrian system, 

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

 certain prominent localities were published, Lower Silurian species. 

 Meanwhile, by adopting the word " Cambrian," my friend and 

 myself were certain, that whatever might prove to be its zoological 

 distinctions, this great system of slaty rocks, being evidently inferior 

 to those zones which had been worked out as Silurian types, no 

 ambiguity could hereafter arise. On the other hand, the adoption of 

 any term derived from a part of the continent, where we had not 

 made ourselves masters of the true sequence, might involve the whole 

 subject in confusion. This would in reality have occurred had the 

 word " Hercynian " been selected, for subsequent researches have 

 taught us, that the greater portion of oldest rocks of the Hartz are 

 younger than the Silurian system, and that their antique impress is 

 due to metamorphic action*. In regard, however, to a descending 

 zoological order, it still remained to be proved, whether there was 

 any type of fossils in the mass of the Cambrian rocks different from 

 that of the Lower Silurian series. If the appeal to nature should 

 be answered in the negative, then it was clear, tiiat the Lower Silu- 

 rian type must be considered the true base of what I had named the 

 Protozoic rocks t; but if characteristic new forms were discovered, 

 then would the C&mbrian rocks, whose place was so well esta- 

 blished in the descending series, have also their own fauna, and the 

 paleeozoic base would necessarily be removed to a lower geological 

 position. 



In a very comprehensive memoir, recently read, which, when pub- 

 lished, will throw a clear light over the ancient rocks of the lake di- 

 stricts, as compared witli their equivalents in Ireland, Wales, and Scot- 

 land, Professor Sedgwick has answered this appeal himself if. Re- 

 examining all the ancient fossiliferous rocks in Cumberland, he has 

 become convinced that they are there divisible into two great zones, 

 referable to Upper and Lower Silurian types, the former surmounted 

 by old red sandstone and carboniferous limestone, and the latter re- 

 posing on some of tlie oldest sedimentary rocks of our islands, the 

 Skiddaw slates, in which no organic remains have been detected. 

 Numerous fossils from the Berwyn mountains, Snowdonia, and other 

 Cambrian tracts, which he collected many years ago (but which, 

 owing to the want of space at Cambridge, have been only lately 

 unpacked), have been recently subjected to the same interrogatory, 

 and have given the reply, that vast as the thickness of strata may be, 

 th(; .same forms of Orthis which typify the Lower Silurian rocks, not 

 only range through what had been termed the Upper Cambrian (Bala, 

 Berwyns, &c.), but also throughout the whole of North Wales. 



• See Geological Transactions, vol. vi. p. 288. 



t Shortly alterwards I'rofessor Sedgwick proposed tlie word " Paloeo- 

 zoic," as a general name for all the older groups, which, preferring to my 

 own, I immediately adopted as involving no theory. 



J Proceedings, No. 82, p. 541. [An abstract of Prof. Sedgwick's paper 

 will appear in an early Number of Phil. Mag.] 



