——s 
TRANSACTIONS OF SECTION C., 783 
of the Boulder-clay, and the third by the peat- and forest-beds which run down to 
below low-water mark. 
All these land surfaces represent periods when the land was higher relatively 
to the sea-level than at present, the deposits resting severally upon them represent- 
ing each a period of depression when the land was relatively lower, as respects the 
sea, than at present. 
It was pointed out that these indubitable earth-movements could not be 
accounted for on the principle of isostasy, or loading and unloading, nor could they 
be explained away by alterations of the sea-level, nor by subterranean denudation, 
and that we must therefore look for their explanation, not to external causes, but to 
forces acting over large areas and hidden deep down in the interior of the earth, 
6.. Tertiary Deposits in North Manzland. By AtFrep Bett. 
After suggesting that local agencies were sufficient to account for the glacial 
phenomena in the centre and south of the island, the writer proceeds to give 
reasons in support of his proposition that the deposits in the north, instead of 
being, as usually supposed, of glacial origin, are really pre-Glacial, as he finds that 
there are no traces of till or a ground moraine, and that the clays throughout are 
to a large extent free from stony matter, except such as may have been due to 
floating ice, brought in after the shingle beach with Pliocene shells had been 
formed. 
The shells he does not consider ‘ remanie,’ but contemporaneous with the beach 
they occur in, and to belong to the same series of pre-Glacial deposits containing 
similar shells at Wexford, Aberdeen, and Iceland, of Weybourn Crag age, possibly 
an unopened chapter in Pliocene geology. 
Not finding any shingle in the cliffs, he concludes that the rolled stones on the 
beach are far travelled, having no connection with the island deposits. 
The list of shells is the first localised one of any of the deposits in the island, 
and is supplemented by notices of such species as were not personally collected by 
him at Shellag. : 
7. On the Occurrence of Sillimanite Gineisses in Central Anglesey. 
By Epwarp GRrEENLY, 2.GS. 
The author records the occurrence of the mineral Sillimanite in certain gneisses 
and schists of Central Anglesey, which are traversed by great numbers of sills and 
thin bands of growth, often injected ‘lit par lit.’ There is an absence of chilled 
edges, the granite being quite coarse at the points of contact which have been 
observed. The whole series closely resembles that recently described in eastern 
Sutherland by Mr. J. Horne and the author, but it is also associated with the 
Erenendic gneisses, whose Hebridean or Lewisian aspect has been noted by Sir 
A. Geile, 
8. On Quartzite Lenticles in the Schists of South-eastern Anglesey, 
By Epwarp GREENLY, /.GS. 
The author describes the occurrence of numerous lenticles of quartzite in the 
chloritic schists of Beaumaris. They are generally from quarter of an inch to a 
foot in length, but four large masses also occur, of which the largest, the quartz- 
rock of Pen-y-pare, is a lenticle some 700 feet in length, These quartzite lenticles 
are ascribed to a cataclastic origin, the structures resembling on a large scale 
(except that the matrix is crystalline) those of the mylonites of the N.W. Highlands 
of Scotland. The author also compares them to the ‘ crush-conglomerates’ of the 
Isle of Man, The whole series is probably due to the breaking down of a group 
