part 3] LOWER I'AL.KOZOIC OF AETHOG— DOLGELLEl'. 323 



district which would be expected to show most analogy to Cumber- 

 land: namely, North Wales, the Authors assigned a pre-Upper Bala 

 date to intrusions, petrographically resembling those of the Lake 

 District, invading a volcanic series of the same age as the Lake- 

 District volcanics, and with similar structural relations, and also 

 described faulting of Ordovieian age. This early movement was 

 considered to have acted along the same lines as the Caledonian 

 movements ; but in the Lake District a difference of 15° or 20° in 

 orientation occurred, and the earlier movement resulted in gentle 

 folds of large amplitude without cleavage. He would be glad to 

 know something of the petrographical evidence for the age of the 

 Welsh intrusions, and whether anything was known of the nature 

 of the early movements. 



Dr. J. V. Elsdee said that he was in complete agreement with 

 the previous speakers as to the importance of the Authors' work. He 

 was particularly interested in the occurrence of allanite recorded 

 in the paper. The common association of this mineral with epidote 

 led him lo ask the Authors whether these rocks were epidotized. 

 The distribution of epidote in North Wales possessed considerable 

 interest, since its occurrence in quantity seemed to lie restricted to 

 the eastern part of Carnarvonshire ; and it would be useful to know 

 whether the marked development of epidote in Snowdonia extended 

 into the district now described by the Authors. 



Prof. A. H. Cox thanked the Fellows present for the kind 

 reception accorded to the paper, and Prof. Watts for his most 

 flattering remarks. It was a source of great encouragement to 

 younger workers to receive appreciation from so distinguished an 

 authority as Prof. Watts, and from one who was so widely recog- 

 nized as an expert on the Palaeozoic rocks. The speaker stated 

 that the stratigraphical sequence and structure left no room for 

 doubt as to the existence of a second Dictyonema horizon. The 

 specimens had been examined by Mr. Pringle, and they agreed 

 closely with the species found at the lower horizon. The speaker 

 summarized the petrographical and structural evidence that sug- 

 gested an early Bala date for the intrusions, and pointed out that 

 no acid intrusions were found above the youngest acid eruptives, 

 and no basic intrusions above the youngest basic eruptives. The 

 agreement between the markfieldites of the Dolgelley district and 

 those of Charnwood Forest was exceedingly close, also that between 

 the more basic granophvric rocks in the two areas. The speaker 

 was much indebted to Prof. Watts for affording facilities for an 

 examination of Charnwood slides. The uniformity of individual 

 sills over wide areas was very striking; but there were several 

 examples of laccolites tailing out within the district. He was 

 much impressed by the many similarities between North Wales 

 and the Lake District, as described in Mr. Green's various papers. 

 The strike was regular throughout most of the district under dis- 

 cussion, but folds of low amplitude, which cross the general strike, 

 appear in the south-west, and become more important in the areas 



Q. J. G. S. No. 303. z 



