BRECKNOCKSHIRE AND EAST GLAMORGANSHIRE. 47 



A.t Navigation House, in the middle of the coal-basin, 5^ miles 

 further south, there are only two per cent, of Old Red Sandstone 

 and one per cent, of Millstone Grit in the Boulder-clay, the rest of 

 the included stones being Carboniferous sandstone ; it is unstratifled 

 here, and 350 feet above the sea-level. Nearly all the stones in the 

 Boulder-clay of the Rhondda valleys and the Ely valley, as far 

 as Llantrisant, are composed of Carboniferous sandstone or Cock- 

 shot, the latter occurring angular more frequently than the former. 

 This Boulder-clay is unstratified, so far as the author is aware, ex- 

 cepting near its surface, where it often shows signs of having been 

 winnowed. 



At Pendoylan and St. Pagans, in the Ely valley, the relative fre- 

 quency of occurrence of different stones in the Boulder-clay is about 

 as follows : — 



Pendoylan. 



Lias 18 



Rhaetic 9 



Red Triassic sandstone 9 



Light green dolomitic conglomerate 4 



Carboniferous sandstone 51 



Millstone Grit 5 



Carboniferous Limestone 4 



Too 

 Boulder-clay in section, 15 feet thick unstratified, brown and 

 sandy ; a stiff red Boulder-clay underlies it. A few Chalk flints in 

 the upper Boulder-clay : height above the sea-level 160 feet. 



St. Fagans. 



Lias 38 



Rhastic 1 



Red Triassic sandstone 2 



Red dolomitic conglomerate 8 



Carboniferous sandstone 42 



Millstone Grit 6 



Old Red conglomerate 1 



Old Red Sandstone , 2 



100 

 Boulder-clay in section 15 ft. thick, unstratified, brown sandy clay ; 

 a few Chalk flints near surface ; height above the sea-level 60 feet. 

 The stones in the Boulder-clay at Pendoylan and St. Pagans seem 

 to have a tendency to lie with their lengths E.N.E. and W.S.W., 

 while those in the Boulder- clay at St. George's, halfway between 

 these two places, are arranged generally with their longer axes 

 lying N.N.W. and S.S.E. Included stones in the Ely-valley 

 Boulder- clay appear to be more delicately striated than those in 

 the Boulder-clay of the coal-basin and Brecknockshire. 



An analysis of the stones included in the Boulder-clay shows 

 conclusively that the ice which formed it moved persistently in a 

 southerly direction, as far, at any rate, as the southern outcrop 

 of the Coal-measures. The strike of the different formations in 

 Brecknockshire beyond the northern boundary-line of the Coal- 

 measures runs nearly east and west ; and no erratics from a southern 

 formation have invaded the area of a northern. 



