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



of Graig-ddrwg were at the same time filled with deep accumulations 

 of snow and ice, from which were discharged a radiating series of 

 glaciers, one pressing southward to swell the ice-stream that filled the 

 valley of what is now the estuary of the Mawddach, another through 

 the Pass of Afon Treweryn between Arenig Mawr and Arenig Bach 

 eastward towards Bala and the valley of the Dee, whilst a third, swelled 

 by all the snows of the Manods and the Moelwyns, flowed south-west, 

 into what is now the broad flat of Traeth Bach, there to be joined 

 by another great ice-stream which, partly descending from the high 

 eastern slopes of Snowdon, filled Nant Gwynant, and debouched into 

 the area now occupied by the marshy flat of Traeth Mawr. In all 

 of these the directions of the striations necessarily conform to the 

 trend of the valleys — easterly, southerly, or south-west, as the case 

 may be. 



I mention these specialities of striation partly to show that tbe 

 Welsh group of mountains, as a whole, was not overridden by a great 

 universal ice-sheet proceeding from the far north, as some have 

 ventured to suppose. In the main, every large valley was filled by its 

 own special glacier — a circumstance long ago stated in a broad way 

 by Buckland, and definitely worked out by me for Caernarvonshire 

 in my essay in the first volume of ' Peaks, Passes, and Glaciers,' after- 

 wards republished in a little book. In North Wales, when the 

 country was absolutely full of snow and ice, each great valley yet 

 maintained its separate ice-flow. In such a case, however, there 

 were many deviations consequent on under and upper ice-currents, 

 the upper parts of glaciers diverging from the direction of the under- 

 flow, and passing across what are now low watersheds, like that 

 of Llyn Caw lyd, into neighbouring vales, such as that of the Conwy — 

 a circumstance to which special attention has been called by the 

 Reverend W. T. Kingsley, while engaged within the last few years 

 in sounding the lakes of North Wales, with the view of proving 

 them to be true rock-bound basins, in which he succeeded. 



Such statements as these are preliminary to, and necessary for 

 the understanding of, the main point of this paper, which I will now 

 discuss* 



On the north-west slopes of the Snowdonian range* (see Map, PI. 

 XIV.), great glaciers poured their ice-streams down the valleys of 

 Llyniau Nant-y-llef to the west, and of Llanberis and Nant-fFrancon 

 to the north-west and north; and these never quite reached the region 

 now occupied by the Menai Straits, but, escaping from the higher 

 bounding-walls of their valleys, spread out in the shape of broad fans 

 on the north-western slopes of the minor hills that now overlook the 

 Straits. This is proved by the northerly curve of the glacial striations 

 at the mouth of the Pass of Llanberis, on the flatter area above the 

 Bteep slopes of the slate-quarries by Llyn Peris and Llyn Padarn, and 

 strongly hinted at by the long, smooth, grass-covered terraces of rock 

 that pass from the opening of the valley of the Ogwen north-eastward 

 along the seaward slope of Moel Wnion, and are still further continued 



* I use the word range as a convenient term. There is no range of moun- 

 Saius in North Wales. Taken collectively they form a great group. 



