Correspondence. 283 
CORRESPONDENCE. 
———+~_-— 
THE OUTLIER OF CARBONIFEROUS LIMESTONE NEAR CORWEN, 
NortH WALES. 
To the Editor of the GRoLOGICAL MAGAZINE. 
Sir,—A day or two may be spent with considerable pleasure and 
profit, geologically, in the vicinity of Corwen, North Wales, now 
easily accessible by rail from Llangollen. The hills of Wenlock 
Shale thereabout may yield fossils if well searched. The ‘Tarannon 
Shale’ of the Geological Survey contributes greatly to the boldness 
of the scenery. Five miles north-west of Corwen, on the Holyhead 
Road, there is a romantic waterfall in a patch of the ‘ Bala Lime- 
‘stone,’ and diligent hammering in its immediate vicinity will be 
rewarded by many characteristic fossils. Nearer the village there is 
an outlier of the Carboniferous Limestone which is well worth the 
attention of geologists, both for its own peculiar features and fossils, 
as well as for the relation it bears to the main belt of that formation 
as it is developed on the North-Wales border. 
SW. Quarries. NE. 
: About 35 yards. River Alwain. 
Wenlock Shale. (Unworked.) if e dad. ¢.0.a 
SECTION OF THE MOUNTAIN-LIMESTONE AT CORWEN. 
a. Limestone. b. Black shale with nodules, Rhynchonella, Chonetes, &c. c. Band of 
ferruginous nodules. d. Limestone (Productus giganteus, &c.), rather arenaceous, and 
With a shale band in the middle: 45 feet. e. Dark bituminous shaley beds, with stone 
bands, and layers of drifted Producit. f. Limestone beds, with Phillipastrea radialis, 
Lithostrotion junceum, L. fasciatum, Diphyphyllum latiseptatum (?), and small Producti and 
Terebratulee. 
This outlier (see fig.) rises up out of a plain (in the midst of 
mountains) watered by the Rivers Alwain and Dee, and near to the 
confluence of the two streams. The locality is called Hafod; and 
supposing the wooden bridge over the Alwain is not swept away by 
a flood, as it was when I once visited the spot, you may reach it in 
about a mile and a half from the village ; but, to prevent disappoint- 
ment, it is better to keep to the Holyhead Road until you have 
crossed the bridge by which that road is carried over the Alwain, 
and then, turning immediately to the left, the quarries are reached 
directly. In order to understand the relation in which the outlier 
stands to the main band, it will be well to observe that the latter 
consists, in ascending order—first, of a series of pale-coloured beds, 
much quarried for fluxing material; second, a number of layers of 
hard grey limestone; and, thirdly, an alternation of beds of lime- 
stone and shale, and black dirt, abounding with fossils. The beds 
quarried at Corwen correspond to those in the upper portion of the 
main band; the dirt and shale-beds, together with the fossils found, 
