46 J. W. E. DAVID — GLACIAL ACTION IN SOUTH 



In the Old Red Sandstone area, south of the Beacons, the stones in 

 the Boulder-clay consist entirely of angular, subangular, rounded, 

 and intensely glaciated blocks derived from that formation. Going 

 south into the area of the Carboniferous Limestone, stones are dis- 

 tributed through the Boulder-clay, at the places about to be men- 

 tioned, approximately in the following proportions : — 



In the Neath valley ^ mile below Ystrad-fellte : 



Old Eed Sandstone 90 



Carboniferous Limestone 8 



Millstone Grit : . 2 



100 

 Included stones intensely striated, grooved, and polished ; Boulder- 

 clay red, 12 feet thick, unstratified ; principal lines of glaciation 

 on included stones frequently conform with direction of striss on 

 underlying rock-surface ; height above sea-level 740 feet. 

 In the Taff-fechan valley at Pont Sam Railway-station : — 



Old Red Sandstone 38 



Carboniferous Limestone 62 



Too 

 Boulder- clay in section 30 feet thick, unstratified, height above 

 the sea-level 806 feet. 



In the Taff-fechan valley between Pont Sarn and Pont Sticcill : 



Old Red Sandstone 20 



Carboniferous Limestone 80 



100 

 Boulder-clay in section from 50 to 80 feet thick, composed of 

 fractured masses of Carboniferous Limestone, crunched and bruised 

 against one another and the Old Red Sandstone blocks, and more 

 often roughly grooved and scratched than finely striated or polished, 

 bedded in reddish-brown unstratified sandy clay. Height above 

 the sea-level 808 feet. 



Still further south, near Dowlais Top, where the Boulder-clay 

 rests on Carboniferous sandstone, the percentage of different kinds 

 of included stones is nearly as follows : — 



Old Red Sandstone 3 



Carboniferous Limestone , 26 



Millstone Grit 53 



Carboniferous sandstone 18 



Too 

 Boulder-clay in section about 15 feet thick, unstratified ; height 



above the sea-level about 1200 feet. 



Three miles further south, at Abernant, near Aberdare, the 



Boulder-clay contains stones derived from different formations, nearly 



in the following proportions : — 



Old Red Sandstone 3 



Millstone Grit ,... 12 



Cockshot 2 



Carboniferous sandstone 83 



100 

 Boulder-clay 9 feet thick, unstratified; height above the sea- 

 level 1130 feet. 



