348 Hiward Greenly—Glaciation of N.E. Anglesey. 
IT].—Guacration anp Puystoc¢rapHy In THE NortH-Hast oF 
ANGLESEY. 
By Epwarp Grusnty, F.G.S. 
(WITH A SKETCH-MAP.) 
HE general direction of glaciation in the north-east of Anglesey: 
is from about N.N.E. to 8.8.W., with local variations of a few 
degrees on either side. ‘These are but of minor importance, the general 
trend being remarkably steady, so much so as even to indicate before- 
hand the existence and approximate position of unknown occurrences 
of certain rocks by thin trains of boulders. 
When surveying the country about Llanerchymedd and Rhosgoch, 
I was, therefore, much perplexed by finding large numbers of fragments 
of Carboniferous Limestone. For these could not have invaded 
that district if carried from the known exposures of that rock by ice 
moving in the direction mentioned: as will be evident from a glance 
at the annexed sketch-map (p. 349). 
I even made enquiries from leading farmers whether it was possible 
that they might have been brought in imperfectly burnt lime used in 
agriculture in former times; for none had then been found in the boulder- 
clay, but only upon the surface. The farmers thought this was 
possible, and for a while I rested in that view. But fragments of the 
local Old Red Sandstone then turned up, and last summer, in particular, 
a mass of it no less than 10 feet long, lying on the north-west shore of 
Dulas Inlet, which was even there a little too much to the north for the 
prevalent trend. These, at any rate, were not brought artificially. 
Besides, the Boulder-clay at the mouth of Dulas Inlet is decidedly 
red. Now, at Porth Gwichiaid, some distance to the north, there is an 
excellent section in Boulder-clay, and in this I found unmistakable 
boulders of Carboniferous Limestone with crinoids, beautifully ice- 
worn, besides many others of sandstone and conglomerate of Carboni- 
ferous type. Here, at any rate, there could be no doubt.2 From no 
visible outcrop could these boulders have been derived, and it is evident 
they have come from out of the sea. 
If, now, we produce the base-line of the Carboniferous Limestone 
from where it reaches the coast to the little island in Dulas Bay 
where the tower of shipwreck-refuge is, we shall see that it is curving 
somewhat to the north and west, instead of running out on a north- 
east strike as might have been expected; and if we further produce this 
line, following the curve thus indicated, we shall find that it sweeps 
round the north-east of Anglesey at no great distance from the land. 
This, then, is the source of the boulders of Port Gwichiaid, and this 
is the source of the much more numerous boulders that are scattered far 
and wide over the country about Rhosgoch and Llanerchymedd. 
' As the end of my work in Anglesey is now within sight I may perhaps say that 
this and other short papers already published are portions of continuous glacial work 
in the island. Since coming there some twelve years ago I have put the drift lines 
and allied information upon the six-inch maps as well as the ‘solid’ geology, and 
from these a connected account of the glaciation of the island can be given. 
* There seems to be an older set of strize at one place running W.S8.W., but this 
is under high land, and is evidently a local deflection. 
° As large tracts of that country are above the 200 feet contour, we have here another 
case of those uplifts of boulders of which I haye now on record a good number of 
examples in the island. 
