of the South Wales Coal-field. 495 



I have stated (p. 491) that the coal deposit of South Wales, from the mountain 

 limestone upwards, attains, in the deepest part, the enormous thickness of 12,000 

 feet. It will naturally occur to every one, that the accumulation of such a vast 

 amount of material would require the lapse of a great period of time, and as any 

 fact which can afford a probable measure of the comparative extent of such a period 

 must possess some interest, I shall take this opportunity of mentioning one that 

 bears on the subject. 



From the top of a seam of common bituminous coal, about five feet thick, at 

 Penclawdd, on the Bury river, I obtained, in the spring of 1833, a small, worn or 

 rounded boulder of cannel coal, six inches long, four inches wide, and two inches 

 thick. It was almost wholly imbedded in a layer of indurated clay two inches 

 thick, interposed between the coal and the regular roof of hard sandstone, and 

 which touched the upper side of the boulder. After the discovery of this singular 

 specimen, attention was awakened to the subject, and it was found that in the 

 quarries excavated in the enormous deposit of sandstone forming Cilfay Hill and 

 the town hill range from Swansea to the Bury river, there occur many irregular 

 beds of what, from the innumerable pebbles and small boulders of coal aggregated 

 in them, may be termed a coal conglomerate. The coal pebbles are sometimes four 

 inches in diameter, and are confusedly mingled with sand and pebbles of ironstone ; 

 and associated with them have likewise been found small boulders of granite and 

 mica slate. Many casts of Sigillariae and other plants, coated with coal, occur in 

 the mass ; and the difference in the age of this coal and that of the pebbles is beau- 

 tifully illustrated in numerous cases, where the plants have been pressed down on 

 a layer of coal pebbles, which, from their superior hardness, have penetrated into 

 the plants, and thus the newer and older coal have been brought into juxtaposition ; 

 but the crystallization of the former, however distorted the plant may have been, 



munication with some of the gentlemen attached to the geological survey corps of the State, I am per- 

 suaded they exist with equal constancy under the coal-seams of the great Pennsylvanian bituminous 

 district ; and I was informed by Dr. Rogers, whom I had the pleasure to meet in Philadelphia, that they 

 are found in the same relation to the coal in its prolongation in Virginia, with the geological survey of 

 which his name is so eminently connected. 



In a visit made immediately afterwards to some of the coal districts of Nova Scotia, and particularly to 

 that in the neighbourhood of Pictou, near which the Albion mines are worked, I had an opportunity of 

 seeing these Stigmaria beds under upwards of a dozen of coal-seams ; and I was informed by Mr. Poole, 

 who superintends the Albion mines, that similar underlying beds exist in the Cape Breton Island coal- 

 field, where he formerly managed the Bridge Port and Sidney Mines. 



Since my return from America I have visited coal-seams in the neighbourhood of Falkirk in Scotland, 

 and found under them the Stigmaria beds ; I have also evidence that they are in the same way associated 

 with the coal-seams of Ayrshire, where they go by the name of " Fakes " — March 1842. 



