THE GLACIAL DEPOSITS OF WESTERN CARNARVONSELRE. 41 



The place-names in this district are interesting and suggestive. "Grainog" is the 

 Welsh term for "gravel," and it occurs again and again in this neighbourhood, e.g. 

 Bryn-grainog — the gravelly hillock ; Cors Grainog — the gravelly moor ; Ynys Grainog 

 — the gravelly isle, etc. Several spots bear the name of Ynys (island), and these 

 generally mark hillocks or mounds of gravel and sand standing above low marshy or 

 boggy ground which is no doubt underlain by Boulder Clay. Much of this low 

 ground is peaty, and in early historic or prehistoric times was probably under water, 

 leaving the hillocks standing out as islands. Some of these islands may be mentioned as 

 examples : — Ynys-wen, Ynys-y-creian, Ynys-grainog, Ynys-yr-Arcli, Ynys-y-buntan, 

 Ynys-hower ; and there are several others. Most of the spots bearing such names mark 

 hillocks of sand and gravel, but some denote rocky knolls projecting above the low 

 ground, e.g. Ynys-galed — the hard or rocky island. 



Llanaelhiaiarn Gravel Pit. — This lies a quarter of a mile to the north of the 

 village of Llanaelhiaiarn, near the mill situated just off the right-hand side of the main 

 road from Pwllheli to Carnarvon. It is at a distance of 1^ miles from the sea (Carnarvon 

 Bay), and at a height of about 450 feet above sea-level. The section exposed is as 

 follows : — 



2. Brownish-yellow weathered clay, somewhat sandy in places, and with subangular 



boulders especially numerous towards the surface — 6 feet. 

 1. Stratified sands and gravels — 15 feet. 



The beds of sand and gravel alternate, but towards the bottom of the exposure only 

 fine gravelly material and sand are seen. The thickness attained by these gravels and 

 sands is unknown, for their base is not reached in the section. Most of the included 

 stones and boulders are of local origin, but specimens were also obtained of chalk-flints, 

 and of a reddish-streaked rhyolite. 



This pit occurs on the side of a slope which is mostly grassed over. It is 

 probable that the gravels and sands cover considerable areas to the north-east of this 

 exposure. 



Bryn-givydin. — This place lies on the right-hand side of the road between Chwilog 

 and Four Crosses, and near to the latter village. Here the hillock has been dug into 

 for sand and gravel. The section is about 12 feet deep, but is much obscured by talus. 

 Near the surface the material exposed is earthy, but below are beds of coarse gravel 

 alternating with beds of fine gravel. The beds get finer and sandier as traced down- 

 wards. Amongst the boulders are several examples of the reddish-streaked rhyolite 

 which is so common in Lleyn. Just north of Four Crosses there occur pits showing 

 deposits of a similar nature. The sand has usually a greyish colour. No marine shells 

 are detected. West of Four Crosses, on the way to Nevin, some pits are again seen 

 in fields just off the roadside. In these sands and gravels are again exposed, and these 

 are in some of the pits overlain by 4 to 5 feet of bouldery rubble. 



Just east of Penprys, off the same road and at a height of 300 feet above sea-level, 

 TRANS. ROY. SOC. EDIN, VOL. XLVII. PART I. (NO. 2). 6 



