BRECKNOCKSHIRE AND EAST GLAMORGANSHIRE. 51 



on the Millstone Grit, is Pant-Uwyd, half a mile S.W. of the last point. 

 Their trend here is about 38° "W. of S. Traces of them are probably 

 to be found much further westward, as the striae at this last point 

 look very fresh and are firmly cut. The total extent of this 

 striated surface of Millstone Grit from Twyn-cilog on the east to 

 Pant-Uwyd on the west is 11^ miles ; and the striae at either end 

 make with one another an angle of 75°. This extent of convergence 

 seems clearly to imply that the ice which produced these striae radi- 

 ated from the Beacons. 



Going south, down the Neath valley, towards the steep scarp 

 of the Coal-measures, a striated surface of Carboniferous sandstone 

 is to be seen at the top of the cutting at the east end of the trend 

 on the Neath- valley Eailway, between Hirwain and Glyn Neath. 

 This striated surface, which has been exposed from under a sheet of 

 Boulder-clay from 12 to 15 feet thick, is fairly flat ; and the trend of 

 the striae is about from 80° to 85° E. of N. and W. of S. The 

 author was unable to determine the end from which the striae 

 started ; if it be at the east end, as seems most probable, they may 

 have been caused by glaciers from the Beacons deflected into the 

 Neath valley by the steep northern scarp of the Coal-measures, 

 or may be connected with the striae at Craig-y-gaer, and be due to 

 the Scandinavian ice-sheet; if they. begin at the western end, they 

 may be deflected striae belonging to a great glaciation from the 

 north-west, of which there are possible traces at many points in the 

 area of the Coal-measures. 



The author has not ascertained the height of these striae above the 

 sea-level ; but they are probably not much over 700 feet, whereas 

 Cam Mosyn, the highest point in the escarpment, 2 J miles south of 

 this point, is 1971 feet high. 



l^mile east of Cam Mosyn a mamillated surface of Carboniferous 

 sandstone is grooved and striated in a direction about 58° E. of S. 

 Height above the sea-level, as taken by aneroid, 1530 feet, distance 

 from Beacons 12 miles, fall 115 feet per mile. 



1| mile further east some faint scrapes (?) on a shattered surface of 

 Cockshot point in about the same direction ; their height above the 

 sea-level is 1417 feet, as taken by aneroid ; distance from Beacons 

 11^ miles; fall about 130 feet per mile. 



Neither of these striated surfaces can be connected with the 

 glaciers of the Beacons. At Abernant, near Aberdare, 4 miles east- 

 wards, the trend of the striae, on a mamillated surface of Carboni- 

 ferous sandstone, is 18° E. of S. Their height above the sea-level 

 is 1130 feet, as taken by aneroid; distance from the Beacons 11| 

 miles ; fall about 170 feet per mile. At Navigation House, 7 miles 

 distant from the last point, and bearing 35° E. of S., the trend of the 

 striae, on a mamillated surface of Carboniferous sandstone, is 20° E. 

 of S. ; height above the sea-level, as taken by aneroid, 350 feet ; 

 fall from the Beacons, 17 miles distant, about 150 feet per mile. 



Bearing 38° E. of N. from last point, 3| miles distant, there are 

 striae, on a smoothed surface of Carboniferous sandstone, on Gelligaer 

 Common, about 300 vards N.N.W. from the ruins of Capel Gwladis. 



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