488 



ME. W. B. R. KING ON THE 



[vol. lxxix, 



water to the River Vyrnwy, which itself follows the line of 

 the Ashgillian for some distance. 



GHaciation appears to have had little effect on the general 



topography, except partly to fill the valleys with a grey-blue 



Fig. 1. — Map of part of the Berwyn Hills. 



BALA 



N 



4- miles 



[Map 1 is fig. 2, p. 493, and Map 2 is fig-. 3, p. 496.] 



boulder-clay of local origin. The streams have generally cut 

 through this filling of glacial drift to a depth of some 30 feet, and 

 frequently expose the solid rocks in the valley-bottoms. 



