CAMBRIAN SERIES IN N.W. CAERNARVONSHIRE. 315 
opposite sides of the dyke; but higher 
up the hill, where the dyke thins, some 
felsitic-looking grit appears below the 
~ 
KS 
Ar 
we 
te 
Se 
i 
=i 
eal 
17 NY 
conglomerate. a igen 
By the tramway on the north-eastern e 
side of the lake, we pass in going from = 
Llanberis three masses of the conglome- re 
rate; but there is little doubt that it is snc 
only one and the same group of bands 2 ° 
repeated by folding, and that the section g 
is as annexed“, an anticlinal and a e 
synclinal repeating the conglomerate and ® 
overlying slates, so that the green grit & = 
beneath it is only visible once. On this 5° 
supposition the conglomerate varies con- 2 
siderably in thickness in a short distance; g 
but a sort of “rain-spot” rock at the g. S 
base of the middle mass might very well sq aS 
represent part of the southern and 2 S 
thicker. The actual junction of the z = 
northern mass of conglomerate and the x 2 
felsite is masked, but the one can be seen a 3° 
within about a yard of the other. This = ZR 
last conglomerate has, no doubt, a rather Q S: 
“melted down” aspect; but, as Dr. Hicks 2 = 
has pointed out +, here as elsewhere, this dz S 
quite disappears when the rock is J) = 
weathered. Its superficial character is 2 by 
also evident on microscopic examina- = % 
tion. I have had slides prepared from “> ~ = 
different parts of the section described  —& Sy 
above, from the finer variety noted in z. iw 
the railway-cutting on the opposite shore 5 = 
and, as already mentioned, from Moel * © hy 
Tryfaen. With considerable variety of a2 = 
detail the general character of these is 2 = 
sunilar, so that a minute description of 2, > 
each slide is hardly needed. They consist s 
of fragments of quartz-felsite, often very i 
characteristic of that which we have been ~~ 
describing, slaty and gritty rock{, sub- J 
angular and rounded quartz grains, and & 
broken felspar crystals, among which, 8. 
though rather decomposed, both ortho- ~“ 
clase and plagioclase may be recog- = 
* This, I find, is Prof. Ramsay’s opinion, = 
Mem. Geol. Survey, vol.iii.p. 144. o 
+ Quart. Journ. Geol. Soe. yol. xxxiv. p. 151. ai 
t Varieties of flinty argillite and fine quart- 
zite are common among the larger pebbles, 
together with the quartz-felsite pebbles and 
fragments. 
