lEO 



WOOD COAL. 



noticed in a subsequent chapter. The Kimmeridge clay in the oolites 

 also contains beds of shale impregnated with bitumen, which is used 

 as fuel in a country where coal is extremely dear. 



The wood-coal of Bovey Heathfield has been already noticed. 

 I may state in addition that T visited the mine in 1815 : it is worked 

 like an open quarry ; it had been for some years previously under 

 water, but was then laid dry by pumps. There are several irregu- 

 lar beds of lignite or wood coal alternating with what is called dead 

 coal, which is less inflammable, and resembles a bituminous shale ; 

 the beds wedge out narrow as they descend. The whole mass is 

 more or less bituminized ; but the upper part, which preserves the 

 woody structure more perfectly, seems to be composed principally of 

 clay. Sulphate and carbonate of iron occur in some part of the 

 beds, and rounded pieces of maltha. Wood-coal occurs chiefly in 

 diluvial deposits. Where wood-coal is covered with basalt, it is con- 

 verted into a substance nearly resembling mineral coal. This coal 

 occurs in Iceland, in the north of Ireland, and in many basaltic dis- 

 tricts on the Continent. 



Before concluding this brief account of imperfect coal formations, 

 out of the limits of the regular coal formation, I would direct the 

 attention of geologists to two situations, in which coal is found, that 

 are well deserving of notice. The first is the mine of Entreveines, 

 situated in a mountain valley about 2000 feet above the lake of An- 

 necy, and at least 3500 feet above the level of the sea. The bed of 

 coal consists of three minor beds, separated by thin seams of clay 

 varying in thickness, yielding about four feet of good coal, which 

 has the character and fracture of mineral coal ; it is shining, does not 

 soil the fingers, and is highly bituminous, being used exclusively for 

 the gas lights in the cotton mills at Annecy. The total thickness of 

 the sandstone, shale, and coal strata, which compose the coal forma- 

 tion in this place, is about one hundred and fifty yards ; they are pla- 

 ced between thick beds of limestone, and dip together at an angle of 

 about seventy degrees.* It is worthy of observation, that the lime- 

 stone beds above and below the coal formation, have the hardness, 

 fracture, translucency, and appearance of the transition limestone at 

 Plymouth ; yet in another part of the mountain, the same limestone 

 is associated with a bed of dark clay, in which I found gryphites, and 

 belemnites, clearly indicating that the bed was analogous to our lias 

 or clunch clay ; and that the limestone associated with it, notwith- 

 standing its mineral character, belonged to the upper secondary stra- 

 ta; and hence that the coal, in geological position, agreed with the 

 imperfect coal formations in the English oolites. Here, then, we 

 have a further proof of what has before been stated, that in the cal- 



* A particular description of this singular coal mine, with a cut, illustrating 

 the position of the beds, is given in Vol. I, of my ' Travels in the Tarentaise,' &c. 



