114 REPORT — 1S7G. 



northern granitic drift. Both drifts (the Welsh and northern) have, to a slight 

 extent, crossed the average boundary, and a few small Arenig boulders have 

 found their way across the estuary of the Dee into the peninsula of Wirral, 

 where they have become mixed with the very abundant northern drift from 

 the Lake district and the south of Scotland. 



The western boundary of the Arenig felstone drift would appear to run 

 from the Arenig range in a N.X.E. direction as far at least as the celebrated 

 Cefn Cave, near St, Asaph, where, to a slight extent, it has become mixed 

 with the northern drift, and Ukewise with erratics probably from the neigh- 

 bourhood of Conway. Few or no boulders from the southern part of the 

 Snowdon range would appear to have found their way over the high table- 

 lands situated to the east of Llanrwst and Bcttws-y-coed, the Snowdon dis- 

 persion having radiated in all directions to short distances only, excepting 

 towards the south. This Arenig dispersion is one of the most remarkable in 

 South Britain. The felstone boulders from the Arenig range have radiated 

 to great distances over an area extending from N.N.E. to E., and to short 

 distances from E. to S.E.- — that is, over the fourth of a circle. The boulders 

 have found their way across valleys and over watersheds and high mountains. 

 In most places they have wholly ignored the configuration of the ground, 

 excepting where gaps in mountain-ranges have facilitated their transporta- 

 tion. A detailed examination of the surface- configuration, viewed in con- 

 nexion with the positions occupied by the boulders, would seem to favour 

 the idea that they could only have been carried by floating ice ; but it ought 

 to be observed that there is an apparent distinction between the large angular 

 and subangular boulders which are seen chiefly on the surface, and those 

 smaller and well-glaciated boulders which are found imbedded in the Lower 

 Boulder-clay at comparatively low levels. 



Among the Arenig felstone boulders, which arc so remarkable for size, 

 for the unexpected routes thej^ have taken, or for the distances they have 

 travelled, as to render tliem worthy of being preserved, the following may be 

 mentioned :—(l) The Cefn boulder, a short distance west of Cefn station, 

 near Euabon, which measures 15 x 14 feet, and at least 10 feet in depth ; 

 (2) the Maendigwycliyn, or great immovable stone in the village of Eryrys, 

 near Llanarmon (about 5 miles east of Euthin), which measures 15 x 15 x 12 

 feet, and is situated about 1130 feet above the sea ; (3) a boulder in a field 

 near Bryn-Cloddian, north-east of Caerwys railway-station, and a few miles 

 south-west of Holywell. 



The direction of glacial strife on rock surfaces in the eastern part of North 

 Wales, as well as in the neighbourhood of the Arenig mountain, Corwen, &c., 

 in general agrees with the course the boulders have taken. On the summit 

 of Halkin mountain, in a quarry a short distance west of Holywell, there are 

 well-defined stria;, indicating the passage of ice from the south-west ; and in 

 the neighbourhood of Llangollen, especially near Trevor (as lately ascertained 

 by Mr. Morton, E.G.S.), there are several instances of stria; pointing from 

 west to east. 



