40 DR T. J. JEHU ON 



by an ancient encampment. The Foel itself is for the most part covered by a mantle of 

 Drift and is grassed over. Several sand and gravel pits can be seen between Clynnog 

 Fawr and Llanllyfni ; as, for instance, just off the roadside above Tai'n-lon, and again on 

 the side of Y Foel, where the material is gravel and in which a south of Scotland granite 

 boulder was picked up. 



At Talarn a new cut for the Afon Llyfni disclosed a section of gravelly drift 440 

 feet above the sea. Sections of similar drift can be seen in most of the slate quarries, 

 but according to Mr Reade its maximum thickness does not appear to exceed 20 feet in 

 the bottom of the valley. This gravelly material has a clayey matrix. 



A gravel-pit of the usual character occurs at Ty-glas, about a mile to the south of 

 Tai'n-lon. 



At Ynys-yr-Arch, when visited by the writer, a trench was being dug out to accom- 

 modate a churning wheel. The section exposed showed : — 



3. Soil— 1 foot, 

 2. Gravel — 4 feet. 



1. Stiff bluish-grey Boulder Clay — 6 feet. (The bottom of this Boulder 

 Clay was not reached in the section.) 



Baron Hill, near Bivlcli-y-denvydd, Pant-glas. — Just below the farmhouse on the 

 north side boring operations in search of water were being carried out. In the shaft 18 

 feet were passed through when the locality was visited by the writer, and the material 

 traversed consisted entirely of typical dark greyish Boulder Clay which was weathered 

 yellow near the surface. Boulders were common in the deposit and were well glaciated. 

 The bottom of this clay was not reached. 



At Llecheiddior Ganol, lying between Pant-glas and Ynys railway station, there 

 occurs a gravel and sand pit. The deposits are bedded, and are coarse near the surface 

 and fine below. The bottom of the sands is not exposed. No foreign erratics were noted. 



At Plus Llecheiddior, just behind the house, a section of the hillock is disclosed. 

 Boulder rubble is seen overlying fine sand which has a depth of 4 feet in the section 

 without reaching the bottom. Gravelly and sandy beds of the usual character were 

 exposed in a pit at Llecheiddior Mill, but the pit is now filled up. 



In the neighbourhood of Brynhir are many mounds and elongated hills of gravel 

 and coarse sand. The included stones are all more or less rounded by water action and 

 apparently consist of locally derived or Welsh material. A rough bedding is usually 

 shown. The ridges are seen to run for most part from north to south. East of Brynkir, 

 at Blain-y-cae, gravel is again seen, but the deposits have become finer, passing into 

 sand, as traced downwards from the surface. 



At Grraianog Farm, near Ynys station, there is a small gravel and sand pit just 

 ;il>ove the house. In this pit a chalk-flint was picked up, and also a granite with reddish 

 felspars and black mica, which is undoubtedly a fair-travelled erratic though its parent 

 rock- li;is not been located. 



