343 Sii- R. I. Murchison on the Silurian Rocks of Cornwall. 



lower and upper limestones ; and 4tli, a limb of the culmiferous 

 or carbouifcrous basin of Devonshire. 



This view willj I trust, be perfectly intelligible to the members 

 of yom' Society who have occupied themselves with the considera- 

 tion of this branch of geology, and on which Mr. R. Q. Couch 

 has recently written with persjjicuity and talent. I doubt, how- 

 ever, if anything I have stated will make a due impression upon 

 one of that number, my good-humoured antagonist the Rev. D. 

 "Williams, whose views of the Cornish succession of strata seem 

 to be opposed to those of all his contemporaries. Geologists, 

 however, who have long lived in Cornwall, and have so well 

 illustrated its mineral structure, will, I am persuaded, be the 

 first to admit the value of the Palreozoic classification, which 

 having been worked out and established in tracts exempt from 

 much dislocation and alteration, has been so applied, as to enable 

 us to interpret the true history of the highly convulsed and me- 

 tamorphosed 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 

 channel, 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 resemblance between the Mounts St. Michael in the 

 two countries ; and no one can have traversed these two regions, 

 without percei\'ing that, just as they e\idently belong to the 

 same mineral tj'pe, so are their respective inhabitants descended 

 from a common stock, whose names of places have passed dowTi 

 to their French and English descendants. The existence of 

 Caradoc sandstones and other Silurian rocks in that part of 

 France hanng been already indicated (Devonian and carboni- 

 ferous strata being also abundantly developed), their discovery 

 in Cornwall is a happy addition to that union of geological and 

 historical records, by which these widely-separated residences of 

 the Celtic race are illustrated. 



"With regard to the highly mineralized or metamorphosed 

 conditions of great poi"tions of the killas and sandstone of Corn- 

 wall, I can do little more than refer you to the few obscr\"ations 

 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 mc- 

 tamorphic rocks of Cornwall on the one hand and those of Scan- 

 dinavia and the Ural mountains on the other ; whilst the paral- 

 lel is now drawn closer by the recent discovery of the Cornish 

 Silurian rocks. Your last eiaipted granites, elvans, and porphy- 

 ries, have played exactly the same part in traversing your Palffio- 



