38 PROCEEDINGS COTTESWOLD CLUB 1910 



further south, less high and less deformed than the Snowdon 

 Group, but possess features evidently connected with glacial 

 erosion. The sketch in which the peaks are named (text-fig. i), 



Fig. I. — The Brecon Pe.iks, named and with Utitudes (£. Burrow) 



shows very clearly indeed the broken tooth-like aspect of their 

 summits, which, as already noticed, is very characteristic of 

 glacially-sculptured mountains, together with the great hollow 

 cwms beneath them. The escarpment faces on the whole 

 a little east of north, and most of the great cwms, whose 

 head-walls impart the broken tootli-like aspect to the summits, 

 have a similar direction. 



This broken tooth-Uke aspect of the summits, as already 

 remarked, is very characteristic of glaciated mountains, and the 

 general resemblance in this respect, and in the great amphi- 

 theatre-like cwms of the portion of the Beacons depicted 

 in PI. XL, to the features as obtained in the neighbourhood of 

 the Grimsel Pass (PI. VIII., fig. i), and at Snowdon, already 

 commented on, is noticeable and instructive. It is rendered yet 

 more complete by the occurrence in the hollow of the great 

 cwm shown in PL XL, of a small moraine-contained (PL XII., 

 fig. i) tarn, locally known as Llyn-cwm-Llwch (PL XII., fig. 2). 



Very similar phenomena of cwm and tarn obtain in that 

 portion of the Black Mountains of Carmarthenshire often 

 known as the Carmarthen Fans ; while at Fan Gihirych, Fan 

 Fawr, and Craig Cerig Gleisind, between the Brecon and 

 Carmarthen Fans, are fine amphitheatral cwms in moel-like 



