of Silurian Bocks in Cornwall. 39 



persuaded, be the first to admit the value of the Palaeozoic classifi- 

 cation, which, having boon worked out and established in tracts ex- 

 empt from much dislocation and alteration, has been so applied as to 

 enable us to interpret the true history of the highly convulsed and 

 metamorphosed rocks of their county. It is, in fact, the greatest 

 triumph which could have been anticipated on the part of those who 

 have steadily proceeded from the known to the unknown. 



Looking from your own country to the opposite side of the Chan- 

 nel, you are doubtless well aware that there is the strongest analogy 

 between the slates and granites of Cornwall and those of Brittany 

 and Normandy. Many persons have remarked upon the strong re- 

 semblance between the Mounts St Michael in the two countries, and 

 no one can have traversed these two regions without perceiving, that 

 just as they evidently belong to the same mineral type, so are their 

 respective inhabitants descended from a common stock, whose names 

 of places have passed down to their French and English descendants. 

 The existence of Caradoc sandstones and other Silurian rocks in that 

 part of Fi'ance, having been already indicated (Devonian and carbon- 

 iferous strata being also abundantly developed), their discovery in 

 Cornwall is a happy addition to that union of geological and histo- 

 rical records, by which these widely separated residences of the Celtic 

 race are illustrated. 



With regard to the highly mineralized or metamorphosed condi- 

 tions of great portions of the killas and sandstone of Cornwall, I cjin 

 do little more than refer you to the few observations I made at your 

 anniversary meeting, and of which a brief abstract has appeared in 

 your newspapers. There are, as you well said in your Anniversary 

 Discourse, many analogies between the metamorpliic rocks of Corn- 

 wall on the one hand, and those of Scandinavia and the Ural Moun- 

 tains on the other ; whilst the parallel is now drawn closer by the 

 recent discovery of the Cornish Silurian rocks. Your last erupted 

 granites, elvans, and porphyries, have played exactly the same part, 

 in traversing your Pala)ozoic sediments, as like rocks have done in 

 Norway. Cornwall may also be compared to large portions of Sibe- 

 ria, and notably to the Ural Mountains, whose chief eruptions have 

 taken place through deposits of Silurian, Devonian, and carboniferous 

 age. In both countries, the eruptive rocks are granites, porphyries, 

 greenstones, and serpentines : even in their superficial accumulations, 

 there is this striking resemblance, that the Cornish detritus and gra- 

 vel (as clearly pointed out by Mr Carne) is purely local; — the 

 county being quite as exempt from all far transported materials as 

 the Ural Mountains and Siberia. With this absence of all foreign 

 transport or drift, Cornwall is as instructive as the Ural in never ex- 

 hibiting those " roches moutonnees," and those polished and striated 

 surfaces, which have been so erroneously referred to the action of 

 land glaciers, in all those low regions of the earth where they have 



