37? 



earth ; but was unable to adduce any direct, and positive, evidence, 

 in favour of this opinion, owing to the refractory nature of the 

 silex, which 'demanded such agents to effect its separation, as would 

 not fail to occasion a decomposition of the vegetable, or bituminous 

 matter, with which it was combined. In calcareous fossil wood, 

 which I suppose to differ from the former, merely in the nature of 

 the earth thus introduced, the same difficulty does not exist; since it 

 will yield to the action of less destructive agents, and will allow of 

 the complete separation of the superadded, from the original matter. 

 Thus, by the addition of the mineral acids in a state of dilution, it 

 might be expected that the carbonate of lime would be decomposed, 

 and that the interposed particles of earth might in this manner be re- 

 moved, leaving the vegetable or bituminous matter, in that state, in 

 which it existed, when its particles were first, perhaps some thousands 

 of years since, involved in this stony mass. The result of such an 

 experiment might also afford some elucidation of the question, re- 

 specting the formation of silicious wood; since if the original matter 

 could be plainly made out, in the case of calcareous fossil wood, 

 the inference would undoubtedly be admitted, that it was the same 

 in the silicious fossil wood, and that in both cases the lapidifying 

 change had been effected by impregnation, and not by substitution. 



A piece of the light-coloured fossil wood of Oxfordshire, already 

 described, was immerged in nitric acid, diluted with about four 

 times its bulk of water; a considerable degree of effervescence en- 

 sued, which lasted several hours ; at the end of which time, the car- 

 bonate of lime being completely decomposed, the original matter 

 of the wood had fallen to the bottom, in the form of a dark, fine, 

 umber-coloured, flocculent sediment; the carbonate of lime having 



o 



been so thoroughly diffused between these light particles, as to have, 

 been their only bond of connection. A portion of this sediment, 

 after having been washed and dried, was placed on a red-hot iron, 

 when it directly inflamed, and was quickly consumed. 

 VOL. I. 3 c 



