Vol. 54.] IN SOUTH WALES, DEYON, AND COENWALL, 271 



near Treforest, and a striated surface under Boulder Clay 12 to 15 

 feet thick at the western end of the tunnel at Pen-cae-draen, between 

 Hirwain and Glyn Neath, in the Neath Valley, the striations being 

 in the general direction of the valley, though 400 feet above the river. 

 This was as far as Prof. David followed the evidences of glaciation in 

 that direction, but there is a similar deposit lying on a planed surface 

 of Coal Measure sandstone at a corresponding level 2 miles lower down 

 the valley, where the railway cuts into the eastern side near Hendre 

 Wyddel, and Boulder Clay and erratic blocks are to be found all 

 down the valley. 



The section of Boulder Clay near Cwrt Sart has been noticed. 

 It is about as far from the Brecknockshire mountains as the Boulder 

 Clay near Treforest, and 10 miles farther north than the Boulder 

 Clay at a corresponding level at St. Pagan's, It would seem that 

 the Boulder Clay which, in the upper part of the Neath Valley, Prof. 

 David considered to be the product of land-ice descending from the 

 Brecknockshire mountains, extends down to the mouth of the river, 

 where it now lies far below sea-level, and it would appear that the 

 Neath and Tawe valleys, like the Mersey Valley, are partly filled 

 with glacial deposits. To what extent the scooping out of the valleys 

 may be attributed to glacial action is difficult to say. 



I am not aware of any Boulder Clay in the valleys connected with 

 Milford Haven ; but, with the evidences of glacial action in the neigh- 

 bourhood, it appears reasonable to attribute to land-ice from the 

 Prescelly Hills a share in the excavation and the moulding of the 

 rock-valleys now submerged in Neyland and Milford Pills. 



The evidences of glacial action in South Devon and Cornwall are 

 scanty, but not altogether absent.^ In the Bovey Heathfield, lying 

 unconformably upon the Miocene beds, is a deposit of sandy clay, 

 with a large admixture of angular and subangular stones varying in 

 size from that of a hazel-nut to blocks of a foot in diameter, which 

 has most of the characteristics of Boulder Clay, and in a clay resting 

 upon it the dwarf Arctic birch and willow were found. Erratic 

 blocks and scratched stones have been observed in various places in 

 South Devon : Pengelly described blocks of white opaque quartzite,^ 

 some as large as 10 x 3| x 3 feet and 10| x 5^ x 3 feet, which are 

 found resting on Devonian shale, or sometimes ' in a heterogeneous 

 accumulation of clay and stones *^ in the neighbourhood of Tamerton 

 Foliot, and which he calls ' whitakers.' That, however, is a local 

 name for a white spar, and is not the name of any particular blocks ; 

 erratics of the same material, and also of Dartmoor granite, strew 

 all the neighbourhood down to the level of the river Tavy. Many 

 are built into fences, while many remain in the soil. The blocks 

 described by Pengelly are probably those near Blaxton Parra. One 

 group is on the water-parting between two valleys tributary to the 

 Tavy, and about 400 feet above the sea. Another group is on the 



1 W. Peugelly, Trans. Devon. Assoc, vol. xv (1883) p. 369. 

 * Ibid. vols, vii, ix, xii (1875-77-80). 

 3 Ibid. vol. xii (1880) p. 311. 



Q. J. G. S. No. 215. X 



