330 



specimen has been engraved, I have obtained other specimens of 

 this fossil wood, in which the loose and shivery texture of rotten- 

 wood is still more decidedly manifest. This kind of fossil wood 

 appears to be that to which the term of SILICIOUS WOOD may be 

 most appropriately applied. The second kind of silicious fossil 

 wotod is that which, previous to its impregnation with silex, had 

 undergone the change which the bituminous fermentation induces ; 

 this kind of fossil wood may be termed SILICIZED BITUMINOUS 

 WOOD ; and its several species will be found to have depended 

 much, for their general appearance, on the degree to which the 

 bituminizating process had proceeded, in the wood, previous to its 

 lapidefaction. 



Bituminous wood, we have seen, may exist in two states ; in one, 

 the fibres, although rendered bituminous, and perhaps softer than 

 in their original state, have not been so far changed as to run toge- 

 ther and destroy the natural separation which exists between them. 

 A specimen of bituminous wood in this state, dug up at BJackwall^ 

 is represented at Plate I. Fig. 1. In the other state, the bituminous 

 fermentation appears to have proceeded so far, as to have occasioned 

 such an approach to fluidity, in the bituminized wood, as to have 

 allowed it to run together in a mass, by which the ligneous texture 

 and fibrous appearance have been lost. The Bovey-coal, of which 

 we have already spoken, and which has been figured in Plate I. 

 Fig. 3. is an example of bituminous wood, which has existed in this 

 state. In specimens of this wood, its state of softness, nearly ap- 

 proaching to fluidity, may be inferred from the fibres, in one part 

 of a specimen, being disposed in various distorted directions, very 

 different from those which naturally belong to the woody fibre, 

 whilst, in another part, they seem to have run together in one mass, 

 in which every trace of fibrous texture is obliterated. 



SILICIZED BITUMINOUS WOOD may, therefore, agreeable to these 

 two different states, in which bituminous wood has existed, be 



