302 



impregnation ; and in some parts very considerable vacuities have 

 been formed. In its present state, exceedingly small silicious crys- 

 tals invest every fasciculus, and line every interstice and cavity, but 

 without proceeding so far as to entirely obliterate them, or in the 

 least to alter the regular structure of the wood ; all the remaining 

 parts of which appearing to retain their natural shape and situation. 



That such an investiture of crystallization, spreading almost over 

 the whole surface, could have been thus regularly disposed, from 

 an injection of flint rendered fluid by heat, without obliterating the 

 small cavities, and interstices of the wood, by the introduction of the 

 melted matter, and without affecting the regular structure, or even 

 the colour of the wood, is hardly to be conceived ; whilst the 

 supposition of the silicious matter having been gradually applied, 

 from an aqueous menstruum, offers us, comparatively, no difficulties 

 to encounter. 



In the concluding part of the Doctor's observations, two positions 

 are laid down ; first, that if it had been by an aqueous solution, 

 that the wood had been penetrated, and consolidated, all the parts 

 of that body would be found in the same natural shape and situa- 

 tion ; secondly, that the woody structure is variously broken and 

 dissolved by the fusion and crystallization of the flint. With respect 

 to the first of these positions, it certainly does appear to be unten- 

 able, since many specimens of fossil wood bear the strongest marks 

 of having suffered much from decay previous to their impregna- 

 tion ; and surely, from long maceration and agitation in water, the 

 pressure of surrounding hard bodies, and the numerous accidents 

 to which this wood may have been exposed, previous to its impreg- 

 nation, it would not be surprising, if, after its consolidation, by the 

 means of an aqueous menstruum, all its parts were not found in 

 their natural shape and situation. On the other hand, specimens 

 are frequent in which the natural shape and situation of the parts 

 are preserved throughout, even to fibres, distinguishable only by 



