174* PROCEEDINGS Ol THE GEOLOGICAL SOCIETY. [Jan. 6, 



contemporaneous submarine volcanic rocks alternated frequently 

 with beds containing Lower Silurian fossils ; such masses having 

 been subsequently penetrated by other eruptive matter. Those con- 

 temporaneous trap rocks were stated to be made up of many va- 

 rieties, including felspathic grits, sandstones, conglomerates and 

 breccias, greenstone and hornblendic rocks of many shades, with 

 porphyries, &c. Now, although these rocks had a very different 

 mineral aspect from that with which I was familiar in districts re- 

 moved from such disturbing causes, I never thought of applying a 

 separate name to them. They had, it is true, a peculiar aspect. 

 They were often much swelled out by the interlacement of porphyries, 

 greenstones, and " volcanic grit," and owing to these conditions, 

 fossils were comparatively rare ; but in deciding their age I ap- 

 pealed to the fossils only, and wherever I found certain forms, 

 of Orthidae, Trilobites, Graptolites, &c., I at once mapped in such 

 masses as " Lower Silurian." As no one has ever doubted that 

 the name was there rightly applied, I request geologists to read the 

 chapters descriptive of these rocks *, and then to tell me if I have 

 not in them given a fair illustration (though on a smaller scale) of 

 the leading features which are said to characterize the infinitely 

 grander masses of North Wales. With the exception of beds charged 

 with Lingulae and pisolitic iron ore, and marked by a perfect slaty 

 cleavage, there is, I assert, no essential difference, whether mineral 

 or zoological, between the above tracts of Shropshire and Radnor- 

 shire and the rocks of Carnarvon and Merioneth ; and if the hun- 

 dreds of feet of the one be expanded into the thousands of feet of 

 the other, and the undulating hills ranging from 1200 to I80O feet 

 high be raised into rocky ridges from 2000 to 3000 feet high, geo- 

 logists will have before them, in my opinion, the Cambrian system 

 as now characterized by Professor Sedgwick. 



Nature's legends are, in a word, found to be composed of the same 

 fossil types in the western parts of Wales as in the western limits of 

 the Silurian region ; the only difference being, that in the former the 

 spaces between the letters are vastly more expanded, and that the 

 whole region is more slaty, igneous and crystalline. 



I say it advisedly, and after consultation with good palaeontolo- 

 gists, who have examined the North Welsh fossils, that there is no 

 essential difference between them and those of my Lower Silurian 

 tracts. On the other hand, there are considerable variations in the 

 distribution of the Upper Silurian species of the region I first de- 

 scribed and those of parts of Wales, Cumberland and Westmoreland 

 which have been recognised by geologists, including Professor Sedg- 

 wick himself, as Upper Silurian. Why then does he speak of and 

 apply my Upper Silurian types only throughout his last m.emoir, and 

 not equally depend on those styled Lower Silurian ? Why, indeed, is 

 the term " Lower Silurian " not once employed in his last memoir, 

 though abundantly referred to in all his previous communications, 

 when my types were appealed to? The only answer, it seems to 

 me, which can be given, is that, as the word Cambrian is now de- 

 * See Silurian System, chapters 22 and 26. 



