ON BEDS OF DRIFTED COAL NEAR CORWEN, NORTH WALES. 451 



49. On the Mode of Occurrence and Derivation of Beds 0/ Drifted 

 Coal near Corwen, North Wales. By D. Mackintosh, Esq., 

 F.G.S.* (Read June 21st, 1876.) 



About four years ago the late Mr. Jones, of Angharad, directed my 

 attention to the remarkable fact that beds of drifted coal are to be 

 found in sand and gravel around Corwen, at a great distance from 

 any known coal in situ. The belief that this coal was of local deri- 

 vation had led to unsuccessful mining operations in the Wenlock 

 rocks of the neighbourhood. 



Positions occupied by the Drifted Coal. — Around Corwen the lowest 

 drift consists of yellowish (occasionally bluish) clay, irregularly 

 alternating with beds of coarse gravel. Many large boulders are to 

 be found at or near its base ; and still larger boulders occur at or 

 near its summit. The former are often rounded and local ; the latter 

 subangular, or angular, and erratic (chiefly from the Arenig hills to 

 the west). Above this drift there is a deposit of clean sand and 

 fine gravel, which, in other parts of the Dee valley, often graduates 

 into very coarse gravel with boulders. In many places around 

 Corwen this deposit is covered by an irregular kind of brick clay. 

 The coal is generally found in the sand and fine gravel. Imme- 

 diately to the east of the mountain-limestone quarry (about a mile 

 and a half to the west of Corwen), a roadside section shows fine 

 gravel and sand with streaks of decomposed coal. In the Dee 

 valley, some distance east of Corwen, and not far from Carrog station, 

 considerable quantities of coal may be seen imbedded in sand in the 

 railway-cutting. I was assured that coal may be found in many 

 other places around Corwen ; but the principal instance occurs to 

 the north of the town, and near to where the Denbigh railway 

 crosses the river Dee. In the deep railway-cutting on the north 

 side of the river there are several beds of coal in forms varying 

 from large lumps to fine dust. At the time when the cutting was 

 made the coal kept a temporary smithy going for about a month. 

 The outcrop of the coal-beds may still be seen after removing a 

 facing of sand. The fine gravel associated with these beds, so far 

 as I could see, is almost entirely made up of local micaceous Silurian 

 grit ; and none of the small stones show any decided traces of glacial 

 action, in this respect differing from the boulders in the underlying 

 drift, which are often intensely striated. Northward from this 

 cutting, in the direction of Denbigh, I could find no indications of 

 coal in the sand and gravel ; and this seemed to suggest that the 

 coal could not have been transported from the Yale of Clwyd. 



* Thi3 paper is iutended as a supplement to one entitled "Additional 

 Remarks on Boulders, &c." which appeared in ' Quart. Journ. Geol. Soc.' for 

 December 1874, vol. xxx. p. 711. Since that paper was written, I have traced 

 the dispersion of felspathic boulders from the Great Arenig, in a south-easterly 

 direction, across Bala Lake, and have likewise found Arenig boidders around. 

 Denbigh ; so that thev must hare radiated over the fourth of a circle. 



