THE CAMBRIAN SERIES IN N.W, CAERNARVONSHIRE. 341 



nor did he see any reason to doubt the correctness of his stratigraphy 

 there. 



Dr. Hicks said that he was convinced at the time Mr. Blake's 

 paper was read that his statements in regard to the Bryn-Efail 

 quarry were founded on erroneous observations. Since then he had 

 obtained many important facts proving beyond doubt that Mr. Blake's 

 attempt to overthrow the conclusions arrived at by Prof. Hughes, 

 Prof. Bonney, and himself was based on most unreliable data ; and 

 he had intended ere long to lay these facts before the Society. As 

 Miss Raisin had in this paper brought forward much evidence similar 

 to that which he had obtained, he would confine his remarks mainly 

 to that portion of the area not aj^parently referred to by her, viz. the 

 neighbourhood of the Penrhyn slate-quarries. The very carefully- 

 drawn section which he now exhibited had been prepared by Mr. J. 

 Evans, F.G.S., late Manager of the Penrhyn slate-quarries. It 

 shows the Cambrian succession on both sides of the pre-Cambrian 

 ridge, and the results produced by faults. The zones on the W. side 

 of the ridge are shown to follow one another in exactly the same 

 order as in the more continuous section on the E. side, but the beds 

 on the W. side have been made to dip towards the pre-Cambrian 

 ridge by faults. The basal Cambrian conglomerate can be traced 

 lying on an irregular pre-Cambrian floor. Dr. Hicks had visited this 

 area on several occasions, and he was satisfied that every fossil zone 

 known at present in the Lower-Cambrian rocks of Britain was recog- 

 nizable here ; he had, moreover, collected several new fossils, amongst 

 them, in one of the higher zones, being a large Pai'cidoxkles. The 

 succession clearly shows that the whole of the Lower-Cambrian beds 

 were deposited in a gradually subsiding area, and that the materials 

 were derived by denudation from a pre-Cambrian land containing 

 various crystalline and volcanic rocks and indurated argillites and 

 quartz-rocks. That these Lower- Cambrian rocks were deposited 

 during a period in every respect to be distinguished from the so- 

 called volcanic (Pebidian) period there could not be the least doubt : 

 and nothing could be more unjust to those who had correctly assigned 

 the rocks of the latter period to their proper position, Jbelow all the 

 hitherto recognized Cambrian rocks, than to attempt to merge them 

 in the Cambrian system. 



Prof. Hughes pointed out that the Authoress had met the only 

 strong objection to the view that the felsite ridge was pre-Cambrian — 

 namely, the statement that the felsite altered a slate in contact with it, 

 and therefore must be of later date. This being disposed of, we had 

 now only to consider why the great thickness of rocks seen to pass 

 under the Arenig on either side of the Llanberis ridge of felsite 

 did not appear below the Arenig on the south flank of the Bangor- 

 Caernarvon Archasan axis. He thought it was by overlap, while 

 others were of opinion that it was by unconformity. He and they 

 carried this great deficit to different accounts, and he saw no greater 

 difficulty in believing that so much of the older Cambrian beds 

 had thinned out against an Archaean shore than in admitting that 

 the Arenig sea had here cut off the upturned edges of the older Cam- 



