38 DR T. J. JEHU ON 



clay (fig. 7). Where the peat appears the cliff is low and the sands and 

 gravels disappear. Further east the cliff rises again to heights of about 50 feet, and 

 consists from top to bottom of gravels and bedded sands, the sands forming the lower 

 part. As we approach the Afon Dwyfor end the Upper Boulder Clay, which is here 

 very stony in character, is seen forming the upper part of the cliff and overlying the 

 coarse gravels, which in turn rest on the sands (fig. 8). 



No shell-fragments were seen in any of these deposits, and the pebbles and boulders 

 are all apparently of Welsh origin, no foreign erratic having been noted. 



Sections are again exposed on both sides of Criccieth, where the cliffs consist of 

 the Upper Boulder Clay. A fine section is shown east of the promenade at Criccieth 

 (fig. 9). It is a typical boulder clay containing big boulders which are often beautifully 

 striated and polished. The shore is strewn with blocks and boulders derived from the 

 cliff. No shell -fragments were noted and no foreign erratics. The boulders consist 

 chiefly of greenstones derived from the Snowdonian area. 



III. The Drift of the Interior. 



Away from the coast good sections are not often displayed. The greater part of the 

 interior is covered by a mantle of Drift which often rounds off the lower hills, but the 

 higher mountains rise above all the glacial deposits. Here and there, even on the 

 lower ground, bosses of rock protrude through the Drift, and these often show rounded 

 outlines and a more or less glaciated aspect, but the smoothness has generally been 

 much destroyed by long exposure to the weathering agents. 



The region between Carnarvon and Afon wen is for most part bleak and dreary. Not 

 only is there a deep covering of the superficial deposits over this area, but the Drift 

 often forms mounds, ridges, and elongated hills. Many large boulders are still seen 

 strewn over the surface, although the land has been to a great extent cleared of the 

 loose stones which have been used in building cottages, farmhouses, and the walls and 

 dykes which now form a network over the whole country-side. In the hollows and 

 lower parts peat occurs, as, for instance, at Pant-glas, where it is being cut to a depth of 

 4 feet, and again north of Ynys. 



The undulating plain of Drift rises gradually from the coast-line at Dinas and 

 reaches a level of about 400 feet at Penygroes. Between Penygroes and Clynnog Fawr 

 lies Y Foel — a hill rising G50 feet above sea-level. At the summit of this hill there is 

 an outcrop of slaty rock, but with this exception the entire hill is rounded off with 

 Drift. Sections of the superficial deposits can be seen on the banks of streams, in 

 railway cuttings, and in gravel-pits on the surface or sides of the moraine-like hills. 

 Borings made for water often throw light on the deeper deposits. The mounds and 

 hills of Drift which rise above the general surface of the plain are made up of roughly 

 bedded coarse grey sand, gravels, and boulder gravel in which some large angular and 

 subangular boulders are frequently seen. The materials are for most part of local 



