$. III. DIST. CHAR. Mode. 59 



and an infiltration of stony matter, until the original 

 bodv is superseded by a complete petrifaction. 



xhibits a ligneous conformation ; yet the only evidence it yields of 

 its origin, on a portion of it being submitted to distillation, is a 

 faint empyreumatic smell. To render Mr. Parkinson's theory ad- 

 missible, there ought to be, as lias been most justly observed, a 

 much greater quantity of inflammable matter contained in silici- 

 n'ed wood, than is found actually to be the case; " for it is not con- 

 ceivable that the materials of a few grains of carbonated hydrogen 

 and a drop or two of empyreumatic acid should be capable of re- 

 taining the minute and intricate texture of a piece of wood/' 

 v. Akin's Ann. Rev. Vol. III. p. 305. 



A Vith respect to the state in which vegetable matter existed,previous 

 to its mineralization, we perfectly agree with Mr. Parkinson, and con- 

 ceive there can be little doubt, that the wood has been bituminized, 

 at least in many instances, from which the petrifaction has received its 

 structure. But, allowing this, we see no reason to reject the hypothesis 

 of a gradual removal of the organic matter, during the substitution 

 of the mineral particles. Bitumiuated substances, and even bitumen 

 itself, though not liable to spontaneous alterations like recent vege- 

 table bodies, are still susceptible of decomposition a long mace- 

 ration in water, aided by concurring circumstances, is known to 

 bring about this change, (v. Hatchett. Linn. Trans. Vol. IV. p. 

 1 51.) Why may not, therefore, the disintegration of the particles 

 of bitumiuated wood take place, even after its fibres have been 

 ourrounded, and its pores filled, by an infiltration of silicious matter ? 

 A body thus circumstanced is not impervious to water; and there 

 seems to be no established fact to oppose the supposition, that, in 

 process of time, the vacuities, made by the decay of the vegetable 

 matter, would be filled by posterior impregnations of silex. 



The diificulty of accounting for the colour of petrified woods, by 

 the theory of a gradual substitution, would doubtless be great t 

 were the petrifactions in question really coloured, according to 



