A. C. RAMSAY ON THE ISLAND OF ANGLESEY. 119 



across the Aber valley towards Penmaen-mawr. These, when stand- 

 ing on or near them, are barely appreciable — but seen from Beau- 

 maris across the Lavan sands, form unmistakable features in the 

 landscape. I have often thought (though this is yet unproved) that 

 the broad mound of glacial debris on which Penrhyn Castle stands 

 may only be the relics of the terminal moraine, at a comparatively late 

 period of the history of the large glacier that flowed down the valley 

 of Nant-fTrancon and the Ogwen, fed by the snows of the Glyders, 

 Foel-goch, Mynydd Perfedd, and Elidyr-fawr on one side, and by 

 those of Carnedd Dafydd, Carnedd Llewelyn, and Foel-fras on the 

 other. 



It thus appears that at this period the glaciers of Snowdonia did 

 not cross the Menai Straits into what is now the island of Anglesey; 

 and it is therefore clear that the north-east and south-west striations 

 which mark the whole of that broad region must have been pro- 

 duced by some other power. 



These striations point directly to the mountains of Cumberland, a 

 country which, lying further north, was at one time buried so deeply 

 under snow and ice, that almost all its mountains look simply like 

 gigantic roches moutonnees ; for Cumberland was far more intensely 

 glaciated than the more southern region of Wales. From Cum- 

 berland a vast mass of ice flowed southward ; and, reinforced by 

 the ice-streams that came from the mountains of Carrick, in the 

 south of Scotland, and perhaps even from the basin of the Clyde, 

 it overspread the region now occupied by the shallow sea of 

 Morecambe, Lancaster, and Liverpool bays, that lie between Cum- 

 berland and Anglesey (nowhere more than 30 fathoms deep), and 

 pressing still further to the south-west, covered the whole of the 

 low ground of Anglesey, and went to some unknown distance beyond. 

 Furthermore, in my opinion, so great was the size and power of this 

 ice-flow, that it hindered the glaciers of Llanberis and Nant-fTrancon 

 from encroaching on the territory of Anglesey, and these simply 

 joined the larger on-flowing glacier as minor tributary ice-streams. 

 For this reason it happens that the glacial striations of Anglesey, as 

 we might at first expect, do not point towards the old glacier -valleys 

 of Snowdonia that open on the Straits, but run at right angles to the 

 courses of these comparatively minor glaciers. 



If we now turn to the rocks that form the banks of the Menai 

 Straits, we find that they chiefly consist of nearly flat-lying Carbo- 

 niferous strata (see Map and Section, PI. XIV) ; and looking at the 

 disposition of these strata from Traeth Melyn, opposite Caernarvon, 

 to Llanfair-pwll-gwyngyll, in Anglesey, and on the opposite shore 

 from Caernarvon to Bangor, there is reason to believe that from end 

 to end they once filled the whole of the region now occupied by the 

 Straits. The larger part of this region, as it now exists, is of Carbo- 

 niferous Limestone age ; but it by no means consists entirely of solid 

 limestone. On the contrary, numerous bands of shale and friable 

 sandstones and conglomerates are intermingled with the limestones, 

 together with beds of soft red marl. On the coast opposite Caer- 

 narvon, the low cliffs are entirely formed of red marl overlying the 



