76 PEOF. A. H. GEEElJf Olf A SECTIOJT iST}AE LLAJ!fBEElS. 



north-west, and the conglomerate creeps over the flaky rocks 

 with a rapidly increasing thickness till it conies down to the level of 

 the railway. This conglomerate has the same character as that seen 

 on the other side of the flaky rocks ; it contains a few fine slaty 

 bands which give the dip and show that the beds are rnnning down 

 at moderate angles to the north-west. I could not see the actual 

 junction of the flaky rocks with the grits to the south-east of them, 

 but I traced the two to within a few feet of one another, and it 

 seemed likely that they were separated by a fault. 



Eig. 2. — Enlarged Section hetiueen the j)oi7its P and Q, in fig. 1. 



N.W. S.E. 



Conglomerate. , Grit. 



Dyke. 



c 



A. Fissile flaky rock. B. Greenish-grey fragmental rock. 



C. Grey breccia. 



There seems to me no room for doubt that in this section we see 

 the top of a projecting boss of a group of rocks underlying the 

 Harlech and Llanberis beds, and that the conglomerate rests on these 

 rocks with the strongest possible unconformity. 



Further proof of the unconformity is found when we examine the 

 hill side on the north-east of the railway. Por some way up (fig. 3) 



Pig. 3. — Section at right angles to the Railivay, hetiueen the points 

 P and Q,. 



S.W. IST.E, 



Eailwav. 



we find the fissile rocks peeping out every here and there in gullies 

 and other depressions, with the conglomerate lying upon their edges. 

 I am afraid it may be thought that I have been unnecessarily 

 prolix in my account of this small section, and I certainly should 

 not have thought that there was any need to give, at such length, the 

 evidence for what seems to myself a very simple matter, if it had 

 not been for the following circumstance. I believe that the section 

 just described is the one figured by Sir A. Eamsay in the Survey 

 Memoir on Xorth Wales (pp. 178, 179, figs. Q2 and 63), and he 

 there gives a reading of it very different from my own. He calls 



