CAMBRIAN IX CAEENAEYO>- SHIRE. 257 



cannot, therefore, be the slightest doubt that there is here a coarse 

 lelsitic conglomerate in the midst of the banded series. 



Farther south, on the western slopes of Mcel-y-Ci (see fig. 6, p. 253), 

 "we find again huge crags of very coarse felsitic conglomerate, 

 coming up from below the hard Banded Slates of the mountain as 

 observed by the dip of the latter, and this may be traced on the 

 same S.'VY. strike as far as the crag called Careg-y-gath. Below 

 this conglomerate, between it and AYaen Pentir, there are numerous 

 exposures of the hard banded gritty slates, which, however, become 

 horizontal and almost bend over at the Waen, but are 100 feet in 

 level below the conglomerate crag. 



The fault that has let down the rocks of Moel Ehiw-wen, as 

 determined by other observations, prevents anything of the con- 

 glomerate being seen on its western side, but we pick it up again 

 at Biyn Madog and Dinas ^lawr, the conglomerates of which are 

 well known. These, like the mass near Tregarth, are associated 

 with reddish purple grits, but have large felsite-pebbles and lie in 

 the midst of the banded series, the dips wheresoever observed being 

 to the east. They correspond, therefore, in position as well as in 

 character with the conglomerate at Bangor, and by so doing assist 

 in the correlation of their associated banded beds. 



The rocks which lie below the banded series are distinguished 

 by their more gritty character, and by the greater proportion of con- 

 glomerate and breccia-bands which they contain. The more compact 

 forms are sometimes banded, and very generally show an irregular 

 lamination, but they may occasionally become slaty. This description 

 shows how difficult it may be at times to distinguish them from 

 the rocks at a higher level. It would, in fact, have been natural 

 to class them all together, had it not been that there is a band of 

 rock of a remarkable kind which may be taken as characterizing 

 a definite horizon, and by means of which we can separate off the 

 lower portion of the series. 



§ 8. The Baxgor Breccias. 



These are composed of so peculiar a rock that there is no mis- 

 taking it wherever it occurs. It is never found amongst any of 

 the beds hitherto described, but is more or less repeated at a lower 

 level. Of its nature I need say little, as it has been so well 

 described by Prof. Bonney.^ Sometimes it is almost a grit, some- 

 times almost a conglomerate, but it always contains small angular 

 fragments of slate in considerable abundance ; if these are bluish the 

 rock is bluish, but if they are red the rock also looks red. 



The detailed stratigraphy of the rocks south of Bangor is not of 

 immediate consequence, but I have done the best I can with the 

 six-inch Ordnance map to trace the most probable arrangement, from 

 which it appears that there must be two bands of such breccia, one 

 curving round from Cae Seri to Brynllwyd, and the other from 



1 Quart. Journ. Geol. Soc. vol. xxxv. (1879) p. 317; vol. xxxix. (188o) 

 p. 48U ^C). 



