52 
THE GEOLOGIST. 
the Chartist insurrection, in 1839, and used as a place for making pikes 
and other weapons. The following is the section displayed here, which 
I have obtained, with some others, through the kindness of Mr. Adams, 
the resident manager of the above works. It occupies about 450 feet : — 
Light grey limestone. 
Dark grey do. 
Light do. do. 
Brownish coloured limestone. 
Calcareous shale or marl, containing shells. 
Dark coloured limestone. 
Light blue do. 
Light grey do. 
Light blue do. 
Dark do. do. 
Calcareous shale. 
White limestone. ^ 
Grey do. 
Light blue do. 
Calcareous marl. 
Dark Blue limestone. 
Light blue do. 
Dark blue do. 
Light grey do. 
Dark grey do. 
Calcareous shale. 
Light grey limestone. 
Grey do. 
Calcareous shale. 
Dark coloured limestone. 
Grey do. 
These rocks are tolerably prolific in fossils (principally in the cal- 
careous shales) although not in very good preservation — viz., productus 
comoides, spirifer, terebratula, euomphalus, phanerotinus, lithodendron, 
zaphrentis, and other corals. The walk up the valley, following the 
bed of the Clydach, is, for those who prefer the scenery to the limestone 
sections, of the most romantic description — the waterfalls, especially 
that of the Pwl-y-cwm, will alone repay the pedestrian for his trouble. 
Having arrived at the head of the valley, a short walk over the inter- 
vening millstone grit lands us at Brynmawr. The grit occupies a large 
area of table mountain, and is as boggy and unproductive as most mill- 
stone grits. It consists, in some places, of a quartzose conglomerate, 
and in others of coarse sandstone, glittering with mica. 
