Sir R. I. Murchison on the Silurian Rocks of Cornwall 331 



from the enormous flexures which the strata have undergone in 

 their range from Devon into Cornwall, it is highly probable that 

 Silurian rocks (the equivalents of those alluded to) may be re- 

 cognised in other parts of Cornwall. Thus, the quartzose rocks 

 of Pydar Down or Moor, to the north of St. Columb, which form 

 an east and west axis, dipping to the north and south under fossili- 

 ferous Devonian strata, may (he thinks) prove to be also of Si- 

 lurian age. But, forbearing to speculate on the probable results 

 of future researches, it is my decided belief, that the slaty rocks 

 constituting the great southern headland of Devonshire, at least 

 all the schists, &c. to the north of the Start Point, will eventually 

 be classed with the Silurian group of South Cornwall; for if the 

 Plymouth group of limestones, so prolific in animal remains, 

 afforded us the means of deciphering the age of less clearly de- 

 veloped zones on the same horizon in Cornwall, the Silurian 

 types collected by Mr. Peach may enable us to carry out a more 

 correct classification in still older strata, from Cornwall into the 

 obscure southernmost promontory of Devonshire. In the mean 

 time, confining ourselves to what we now know, it is manifest 

 that Cornwall exhibits in ascending order from north to south, — 

 1st, a band of true Silurian rocks ; 2nd, a zone of intermediate 

 character, forming a transition between the Silurian and Devo- 

 nian systems ; 3rd, a copious Devonian system, characterized by 

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

 or carboniferous basin of Devonshire. 



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

 of your 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 perspicuity 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 Palaeozoic 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 



