BRITISH ASSOCIATION. 



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distinctly proved, and also the high probability of much of the coal 

 ha^dng been formed on the spot ; this view, he stated, was not a new 

 one, it had been contended for by all the Scotch geologists ; Dr. Mac- 

 culloch had supported it, and one Professor had even attempted to 

 estimate the period required for the formation of a seam of coal, by the 

 time occupied in forming a peat bog. 



Mr. Griffith illustrated the mode in which he considered the coal 

 measures had been formed, by describing the general condition of the 

 peat bogs in Ireland ; they appeared to occupy basins which had ori- 

 ginally been lakes, but the peat moss had grown up to the level of the 

 water, and afterwards by capillarity twenty or thirty feet higher. The 

 base of these bogs consisted of clay, covered by a layer of peat com- 

 posed of rushes and flags, above which was another bed of peat closely 

 resembling cannel coal, possessing a conchoidal fracture, and hard enough 

 to be worked into snuff-boxes ; it yielded twenty-five per cent of ashes, 

 and contained a large proportion of oxide of iron. This bed was covered 

 with black peat, containing branches and twigs of fir, oak, yew and 

 hazel, only the bark being left ; and where whole trees occurred, the 

 roots were entirely gone ; the surface was formed of ordinary bog-moss 

 {Sphagnum) nearly white. The whole amount of peat, in this bog, Mr. 

 Griffith thought would form a coal seam at least three or four feet thick. 

 Mr. Griffith also mentioned some of the tertiary lignites of the basaltic 

 region in the north of Ireland, which exhibited a variation in thickness 

 of from three to thirty feet, in the space of a hundred yards. At Lough 

 Neagh these tertiary formations attained a thickness of ninety -eight yards, 

 composed of alternations of wood, coal, clay and sand. 



Dr. Fleming observed, that in attempting to explain any class of phe- 

 nomena, it would be well to begin with the distinct and end with the 

 obscure ; with this view, he recommended inquiries to be instituted into 

 the present character of peat, which presented many analogies to coal, and, 

 like it, was of several different kinds, and found under various circum- 

 stances. He then described a bed of submarine peat off the Shetland 

 islands, resting on and covered by gravel; a lake had been formed 

 within a barrier of sand and gravel thrown up by the sea, and rendered 

 impermeable to water by a lining of mud brought down by rivulets ; this 

 basin had been filled up by the growth of plants, and subsequently the 

 sea had again reduced the barrier, and covered the whole with gravel and 

 shells. In the bay of Aberdeen, after very severe storms, large masses 

 of solid peat were thrown ashore, not unlike cannel coal in hardness and 



