112 The Canibri(i)i and 



Having ascertained, in the years 1840 and 1841, that, on the 

 Continent, the Lower Silurian fossils were the lowest fossil types, 

 I traversed the North Welsh or Cambrian region in 1842, accom- 

 panied by one of my Russian coadjutors, Count Keyserling, to 

 ascertain it' a similar distribution prevailed in Britain. We satis- 

 fied ourselves (leaving all physical proofs to the Government geo- 

 logists, who were then beginning their survey of Wales) that after 

 many apparent flexures, strata containing the same fossils appeared 

 on the flanks and summit of Snowdon, as those which we had left 

 in Shropshire, and to the east flank of the Berwyn mountains, a 

 country which had been specially mapped and described as u Silu- 

 rian." It was, therefore, after foreign comparisons, and after an 

 actual traverse of the so-called Cambrian region, that I published 

 the map of 1843, which, though complained of by my friend, has 

 proved to be correct, and substantially in general harmony with 

 the final results, physical and geological, of the Government geo- 

 logical surveyors. 



I would further refer to the unambiguous printed declarations 

 with which I opened both my discourses of 1842 and 1843, as 

 President of the Geological Society, to prove that I took every 

 opportunity of publishing my conclusions before I issued that 

 map. This, for example, is a small portion of what I printed in 

 1842, — "The base of the Palaeozoic deposits, as founded on the 

 distribution of organic remains, may be considered fairly established; 

 for the Lower Silurian is thus shewn by Professor Sedgwick him- 

 self (I was then speaking of a recent memoir of his own) to be the 

 oldest which can be detected in North Wales, the country of all 

 others in Europe in which there is a great development of the in- 

 ferior strata."* 



As Professor Sedgwick made no opposition to this induction of 

 the author of the Silurian System, nor to another ample illustra- 

 tion of it in 1843, f nothing, it seemed to me, remained to be done 

 in British Palaeozoic classification, except that the Government 

 geologists, who were preparing detailed maps and sections of 

 Wales, should decide whether there were, or were not, fossiliferous 

 strata occupying a lower position than any which had been for- 

 merly described as Lower Silurian. Their reply, in a stratigra- 

 phical and physical sense, is what I affirmed in my last letter, not 

 rashly, but after a careful reference to the maps and sections they 

 have prepared. Taking the tract east of the Berwyn mountains, 

 which I have described as the country of my region, which afforded 

 the fullest development of Lower Silurian rocks resting upon un- 

 fossiliferous greywacke, these geologists have proved that the strata 



* Proceedings of the Geological Society of London, vol. iii., p. 549. 

 t Ibid., vol. iv., p. 70. 



