284 PROF. W. MORRIS DAVIS ON L^ U o' I 9°9> 



name which it contains ; also the smaller Cwm Glas, on the north- 

 east. Between these cwms, in the order named, stretch the south- 

 easter a, south-western, north-western, northern, and eastern spurs 

 from the culminating summit ; the northern spur is ascended hy 

 the upper part of the rack-railway from Llanberis. Furthermore, 

 the mountain-mass as a whole is bordered by three deep valleys, 

 to which the streams from the cwms descend. On the north-easfc 

 is the valley of Llanberis, leading north-westwards from a fine col 

 down to the two lakes, Peris and Padarn (immediately north of the 

 map, PI. XIV), between which are the great slate-quarries on the 

 north and the town of Llanberis on the south ; it may be noted 

 that the upper part of this valley is called the ' pass ' of Llanberis, 

 * pass ' being used here for a stretch of several miles below the col, 

 and not only for the col at the valley-head. On the south-east is 

 the valley of Nant Gwynant, holding the two lakes, Gwynant and 

 Dinas; and on the south-west is the valley of Xant Colwyn. The 

 last two valleys join to drain southwards by Afon Glaslvn, and the 

 town of Beddgelert (pron. Bethgel'ert) stands at their junction. 

 On the north-west the Snowdon mass is continued by a number of 

 moels, which fall off in height towards the Menai Straits ; and these 

 moels stand between the valley of Llanberis on the north-east and 

 the valley of Afon Gwarfai, holding Llyn Cwellyn, on the south- 

 west : the latter valley heading in a broadly open and flat col 

 against the valley of jSlant Colwyn, with which it stands about in 

 line. Wot far from this open col is another col at a little higher 

 level, opening westwards to the valley of Nantlle, to which reference 

 will be made later as a line of glacial overflow. Mynydd Mawr, a fine 

 moel, stands immediately north of the head of JSTantlle Valley and 

 west of Llyn Cwellyn ; its rounded summit, easily accessible, gives 

 a fine view-point for the Snowdon mass. 



Of the figures used in illustration of this article, figs. 22, 23, 26, 

 27, 28, 80, 31, and 32, are from sketches by the author ; 

 figs. 3 and 7 are diagrams based on sketches ; the others are 

 diagrams of ideal forms. 



IV. Geological Structure of the Snowdon District. 



When so short a time as eight days is allotted to so large a 

 problem as the glacial sculpture of Snowdon and its neighbours, it 

 is not to be expected that more attention should be given to questions 

 of geological structure than would be required in identifying on 

 the ground the chief formations described in Eamsay's famous 

 Memoir on ' The Geology of North Wales ' (1866, second edition 

 1881), and coloured on the 1-inch maps of the Geological Survey 

 (Sheets 75, N.E., Pfestiniog ; 78, S.E., Bangor), or that measure- 

 ments of form, height, and distance should be carried beyond those 

 given on the elaborate 1-inch (third edition) and 6-inch maps of 

 the Ordnance Survey. Access to these standard materials while in 

 the field was of great advantage. We enjoyed the recognition of 



