REMARKS ON Mr. SOMERV AIL'S PAPER " ON THE GEOLOGICAL 



STRUCTURE OF SOUTH CORNWALL." 



Br J. H. COLLIN^, P.G.S. 



In a paper under the above title, published in the 27th 

 No. of the Jourual of the Royal Institution of Cornwall, Mr. 

 Somervail has criticised a paper which I brought before the 

 Institution in 1881.*" Mr. Sumervail's paper was read after I 

 had left England, but a reply to its most important statements 

 was wi'itten by my son, who had accompanied me on many of 

 my geological rambles — and was read at the same meeting. 

 Here I was disposed to let the matter rest, but as Mr. 

 Somervail's paper has now appeared in the Journal without my 

 son's rejoinder, I must reply to the criticism myself 



In the first place, let me say that I have nothing to withdraw. 

 I adhere to all the statements made in the paper referred to, 

 and I have corroborative evidence to bring forward in support 

 of some of them. Furthermore — I do not propose to deal with 

 the whole of Mr. Somervail's objections. I will confine my 

 remarks to four only of the points raised by him, the four most 

 important — viz : the age of the " Ladock Beds " ; the existence 

 of certain unconf ormabilities ; the question of the Penryn 

 " gneiss," and that of the age of the " Fowey Beds." 



1. — The, Ladock Beds. — These I have called somewhat doubt- 

 fully Devonian, regarding them as the marine equivalents of the 

 Old Eed Sandstone, as I said in my paper. I still believe that 

 they are "the most recent stratified rocks of Central and West 

 Cornwall, with the exception of certain stratified superficial 

 deposits." In making these rocks Devonian I am in agreement 

 with the Q-eological Survey Maps — and, so far as I know, with 

 every writer on the subject except Mr. Somervail. It is difficult 

 to make out what Mr. S. believes on this point, except that I 

 am wrong. He says on page 268, paragraph 1, "Let me state 

 that I consider it extremely doubtful if any of these Ladock 

 Beds really belong to the Devonian at all." In the next 

 paragraph he says " It is quite possible that the very highest 



* The Geological Age of Ceuti-al and West Cornwall— Jowrn. R.I.C. part 

 I, vol. vii. 



