256 KEY. J. F. BLAKE OX THE E0CE:S MAPPED AS 



spite, therefore, of their somewhat abnormal character, I can only 

 regard these rocks as belonging to this part of the series. 



On the eastern side of the Llyn Padarn felsite characteristic 

 Banded Slate is again seen, but the consideration of its relations 

 must be postponed till the conglomerate of this district is dealt 

 with. 



On the south-east side of the lake we find similar Pale Banded 

 Slates beautifully exposed in the crag at the bend of the road, west 

 of the Glyn Peris Hotel. Here they certainly come below the 

 Khiw-wen Grit. Pin ally, by the side of the Eiver Kothell, at the 

 previously-mentioned locality, we find below the hard red grit some 

 very typical halleflinta with curious lines of lamination. 



§ 7. The Baxgor Conglomerate. 



, This is the well-known band to which attention has been drawn 

 by Prof. Hughes, which is considered by him to form the base of the 

 Cambrian as distinguished from pre- Cambrian rocks, but which I 

 have shown in a previous paper to lie in the midst of the mass of 

 the banded halletlintas alike above and below it, and not to be con- 

 tinuous, but to die out in their midst. The great mass of similar 

 conglomerate, full of huge felsite-pebbles, which crosses the Bangor 

 and Bethesda road 3 i- miles from Bangor, occupies the same position, 

 and it comes up from beneath the mass of the hard Banded Slates 

 already referred to, which in places may well be called halleflinta. 

 But we do not here see below it, as it is the centre of an anti- 

 clinal and is cut off by a fault along the river, on the opposite side 

 of which it is not continued. 



In the strip of country to the west of this, however, beyond the 

 fault which bounds the broken area, we get another exposure of 

 conglomerate in the same position. It is well seen in a small crag 

 by the wayside where the road crosses the railway to the N.W. of 

 Tregarth (fig. 7, p. 253). It here consists of bands of purple grit 

 and conglomerate, capped by a very coarse bed of the latter with 2- to 

 3-inch pebbles of red and white felsite and fragments of purple 

 slate, the whole dipping eastward at 20°. It is seen also in the 

 railway-cutting, where it is followed on the dip by the banded 

 grits ; while on the other side, at Gelli, there is a quarry in banded 

 halleflinta also with an easterly dip, which must therefore lie 

 below it. It thus appears to lie in the midst of the banded series. 

 It may be traced thence in a northerly direction to Bryn Cul, 

 ■where the overlying banded rocks are also gritty, and farther on 

 into a crag by the river-side below Coch Winllan, where it is 

 followed above by green finely-banded halleflinta, all dipping E., 

 and all the exposures of the halleflinta to the west have a similar 

 dip. In the other direction it rises into the great crags of Pandy, 

 where the felsite-pebbles are huge and well rounded, though showing 

 no dip ; but both to the east and the west are crags of banded 

 halleflinta, or hard slate, dipping uniformly east. A similar crag, 

 similarly related, is found at Pronheulog on the same strike ; there 



