430 MR T. J. JEHU ON 



The alluvial flat lying just below Dolbadarn Castle, and separating Peris from 

 Padarn, is made up for the most part of material brought down by the Afon Llwch 

 from Cwm Dwythwch and the heights of Snowdon. It is evident that at no distant 

 date back Llyn Padarn and Llyn Peris formed one continuous sheet of water, and that 

 they are now isolated owing to the deposition of this tongue of sediment carried clown 

 by the tributary stream from the left. Another fact pointing to the same conclusion 

 is that the water-surfaces of both lakes are at the same elevation above sea-level, the 

 Ordnance Survey map giving that of Peris at 339 "5 feet, and that of Padarn at 339 '6 

 feet. 



The distance from the lower end of Llyn Padarn up to the head of Llyn Peris is 

 over three miles. The length of the original lake must, however, have been much greater. 

 For not only is there an alluvial expanse rising very gently from the head of Llyn Peris, 

 and stretching up in the direction of the Pass as far as Gwastad-Nant, but a marshy 

 flat, partly under water and often flooded over after heavy rains, extends from the foot 

 of Llyn Padarn down below Cwm-y-Glo. So, originally, the lake extended without a 

 break all the way from this point up to Gwastad-Nant, a distance of between four and 

 five miles. From a point at a height above Gwastad-Nant, one can see right along 

 both lakes to the lower end of Llyn Padarn (Plate II. fig. 1). Their main axis, running 

 from south-east to north-west, lies in the same line as the Pass, and the lakes evidently 

 fill up the lower end of the valley. At Pen-y-Pass, close to the Gorphwysfa Hotel, a 

 bench-mark indicates an elevation of 1178 feet above sea-level. The height of the 

 alluvial flat, at a point just below Gwastad-Nant, is given on the Ordnance map as 360 

 feet. So the fall is steep from the top of the Pass to the head of the alluvial stretch, 

 after which it becomes very gentle, falling only to 339"5 feet at the water-surface of 

 Llyn Peris and continuing the same in Llyn Padarn. Up above, the Pass is narrow, 

 but at the head of the alluvial strip the valley begins to widen a little. Below Dolba- 

 darn Castle the hills recede from the left side of the valley, which therefore broadens in 

 this region, but further down the valley narrows somewhat again, and it becomes still 

 narrower at the lower end of Llyn Padarn. The river escapes from Llyn Padarn 

 between two rocky knobs on to the marshy flats of Cwm-y-Glo. 



The alluvium lying between the two lakes extends back for a considerable distance 

 along the course of the Afon Llwch. This stream now enters Llyn Peris at its lower 

 left corner. The hills, which slope down to the lake from a great height at the upper 

 end of Llyn Peris and along its right bank, and also on the right bank of Llyn Padarn 

 for some distance below its head, gradually sink to lower levels as traced down to the 

 lakes. The slope down to the margin of the lake is usually steeper on the r'ght side. 

 But here and there, especially in Peris, rocky knobs dip steeply into the water from the 

 opposite or left side. 



Above Llyn Peris and the upper end of Llyn Padarn, on the right side, are the 

 great Dinorwic Slate Quarries. The working of these quarries has sadly disfigured the 

 face of nature. The mountain-side has been torn open, and the vast accumulations 





