Vol. 58.] 
doubtless proceed from the granite in the normal manner. 
PLUTONIC COMPLEX OF CENTRAL ANGLESEY. 
677 
They 
occur in dyke-like masses, forming linear crags running parallel to 
the associated schistose felsite ; that is, east and west in the fields 
Fig. 5.— Vein of granite in felsite, 
north-east of Pen-yr-argae. 
4 
Wustss-=—-< 
ZA) UST S 
“7 T Ar 4477 
“= Ta LAA - 
Bz Pare y 24,3 Lc 
a7) T A GOLA 
EA ON SRO TEST: 4) FEE 
Zoey ATI +s WEN AL ge 
ELE IS AiG LUG 
Ze 
GEA alt A LUCAS * 
2B arn CLL 
LEZ Tie Zee 
= La MA la 
ILE Re oA GLE 
"LZEE EE LEELA 
Ae PLEAS ae 
See: pot L LS Sa 
EZe IE Wane tars 
LANL FARK LEE 
222s te EAA 
Saez |E YX Sag 2 
BELEN Te LEG ES, 
a Sea i - 
Zee EZ |e yy CLE 
ZI AOI ZL 
Lae |? ENG CEeEE ZA FS oP 
NR EE 
ey ee ZEEE 
ZEZEEN A Ze 
So AY 2 
AS yA Bela 
SLL T at Se 
LZ aT YY Zs 
SE ANG Ae 
-& +¥aK i 
\)) 
a 
Ae 
\\ 
\ 
\\\ 
LY 
\\ 
\ \\ 
\ 
\ 
anyi\t 
weQN 
‘\- 
TAN \ 
\ 
» 
\\ 
\\ 
[G=Granite ; K=Felsite. | 
immediately east of Pen-yr- 
argae, and north-east and 
south-west a little farther to 
the north-east. One of the 
dykes was observed to ter- 
minate in thin veins pene- 
trating the schist. Several 
of the crags that trend north- 
east and south-west have 
schist dipping south - east- 
ward clinging to their north- 
western face. 
North-west of Gwalch- 
mai.—-A band of granite 
runs for more than half a 
mile in a northerly direction 
from Gwalchmai, cropping 
out a little to the north- 
west of the Post Office, and 
forming a scarp overlooking 
the western side of the road 
to the north. At the southern 
end of the scarp, the quartz- 
felsite 1s very clearly seen to 
vein the granite, and both 
granite and quartz-felsite send 
veins into the felsite. 
West of this granitic ridge lies a band of the schistose felsite. It is 
about 2 furlongs broad, and is bounded on the west by the granite- 
mass which limits the eastern margin of the gneissic ellipse, the 
junction between the two being near Plas-einion. 
It lies in 
a complex synclinal fold, striking north-east and south-west, in 
accordance with the general trend of the crystalline rocks of Central 
Anglesey. 
It is very well seen at Plas-einion, with a contorted dip 
to the south-east, which, as we go eastward, soon changes to the 
north-west, and this dip is maintained up to the junction with the 
granite of Gwalchmai. 
intrusive veins. 
This schist appears to be almost free from 
East of Gwalchmai, the felsite becomes more and more distinctively 
schistose. 
at Porth Nobla. 
submitted to Prof. Bonney. 
church stands. 
It is frequently penetrated by small granite-veins,* as 
Two thin slices (377 & 378) of this gneiss were 
They are from the field east of 
Bodwrog Church, and are very near to the granite, on which the 
Prof. Bonney considers them ‘a kind of mica- 
gneiss, which may have once been a felsite or micro-granite, and 
1 Mr. Greenly observes that in Central Anglesey ‘quartzose and micaceous 
schists’ are penetrated by granite-veins (Geol. Mag. 1896, p. 495). 
