cambkiax in caerxauvonshire. 20i. 



§ 11. Conclusions. 



The above observations prove that there is a definite succession in 

 the Cambrian series, -which is the same in the isolated portion east 

 and south of Eaugor as in the main mass. Whether we see the base 

 or not depends on the age assigned to the Dinorwig felsite. If that be 

 Cambrian there might be beds of the same system below it, but there 

 probably are none, since we certainly see the base at Beaumaris. 

 Whether we see the top or not depends on whether the Bronllwyd Grit, 

 which belongs to the overlying group, is conformable or not, and 

 there is no evidence that it is. In any case, no inter%-ening beds above 

 the Purple and Pale ISlates are known in North Wales. 



It is also proved that the rocks to the west of the felsite belong to 

 the lower part of the series, and. those to the east to the upper, 

 both being determined in areas where the felsite is absent, and hence 

 it appears probable that the felsite mass is a volcanic complex 

 belonging to the middle of the Cambrian period. 



Thus my former conclusions, though somewhat modified, are 

 shown to be substantially correct. 



Part II. (Abstract). 



It is further argued that a study of the Llyn Padarn felsite proves 

 it independently to be as above supposed, and a post-Cambrian age 

 is assigned to the conglomerates of Moel Tryfaen and Ll^n Padarn. 



PLATE VI. 



Map showing the sequence of the rocks called ' Carahrian ' in Caernarvonshire. 



Fig. 1 represents the northern part of the area, and Fig. 2 is its continuation 

 to the south. Scale: 1 inch = 1 mile. 



DlSCTTSSION. 



Dr. Hicks said it was evident that the Author had on some very 

 important points greatly modified the views advanced by him in 

 his former paper. Mr. Blake now admitted that Miss Paisin had 

 proved conclusively that he had been greatly deceived by the Bryn 

 Efail section, which he had referred to as the crucial spot to prove 

 that the quartz-felsite was intrusive in Cambrian shites. What he 

 had supposed to be baked Cambrian slate had been shown by Miss 

 Paisin to be diabase intrusive in pre-Cambrian quartz-felsite. 

 Dr. Hicks maintained that there was abundant evidence to show that 

 the Llyn Padarn quartz-felsite is of pre-Cambrian age, and also that 

 Mr. Blake had included many pre-Cambrian rocks in his so-called 

 Cambrian succession. It would appear also, from some of the spe- 

 cimens on the table, that the Author had mistaken some crushed 

 and cleaved pre-Cambrian felsites for Cambrian purple slates. 

 The speaker referred to the fact that he had, in the report of the 

 excursion of the Geologists' Association to Caernarvonshire in 1883, 

 indicated the position of each of the zones in the Cambrian, in the 

 section from the Penrhyn slate-quarry to the Kant Ffraucon Valley, 



