Rev. J. F. BlalxB — The Llanberis Unconformity. 173 



wbere Professor Green described it, and was not, therefore, forced as 

 I was to discount its teaching. 



In 1892 I published a detailed account of the Cambrian 

 succession (H),^ from which it appeared that instead of there bein<ij 

 only one Cambrian conglomerate at the base, there were several at 

 different horizons in the series. The facts about the Llyn Padarn 

 felsite and conglomerate were postponed to a later paper. This 

 later paper (I), published in 1893,^ is the one which has been 

 criticized by Professor Bonney and Miss Raisin conjointly in the 

 paper now being replied to (K).^ Prior to the observations therein 

 recorded, most of which were entirely new, I had considered that 

 there was no unconformity beneath the Llyn Padarn — Moel 

 Tryfaen conglomerate, except the supposed local one shown by 

 Professor Green, but these observations forced me to conclude that 

 Professor Hughes and Dr. Hicks were right in their conjecture that 

 such an unconformity occurred, and that it indicated, in the words 

 of Professor Bonney, a " marked physical break." Notwithstanding 

 this, I still agreed with Sir A. Geikie in considering that there were 

 several conglomerates in the Cambrian series, each in relation to its 

 own felsite, but I removed from that series the great one at Moel 

 Tryfaen and Llyn Padarn. 



It thus appears that at that time the whole difference of inter- 

 pretation rested solely on the question as to what were the rocks on 

 which the conglomerate lay unconformably. Dr. Hicks supposed 

 them to be Pre-Cambrian, because the samples he collected in the 

 Moel Tryfaen adit seemed more altered than the Cambrian rocks 

 with which he was acquainted. I held them to be part of the 

 ordinary Cambrian series. I was accompanied in the examination 

 of the adit section by Mr. Robert Lloyd, who has spent his life 

 amongst these rocks and knows them well, and he recognized them 

 at once by their local names. I also exhibited to the Geological 

 Society samples of all that I collected there, without anyone claiming 

 thein as anything but Cambrian. 



But, of course, this difference was fundamental. If the con- 

 glomerate in one place is unconformable to the rocks immediately 

 below the purple slates, we may reasonably expect that in other 

 places it will be unconformable to the latter also, as they follow the 

 former in regular sequence, and in this case the whole proof of 

 there being anything Pre-Carabrian here is entirely destroyed. 



Under these circumstances it is certainly remarkable that Professor 

 Bonney and Miss Raisin, in their criticism upon my paper, do not 

 attempt to show that the rocks in the Moel Tryfaen adit are Pre- 

 Cambrian, but endeavour to demolish my stratigraphy, in which, if 

 successful, they would destroy their own former A'iews and ap- 

 proximate to those which now, on further evidence, I have discarded, 

 and which were nevertheless equally fatal to the idea of there being 

 any proof of the existence of Pre-Cambrian rocks in the district. 



1 Q.J.G.S., vol. xlviii, pp. 243-262. 



2 Q.J.G.S., vol. xlix, pp. 441-466. 



3 U.J.G.S., vol. L, pp. 578-602. 



