. III. DIST. CHAR. Mode. 5? 



ture of the decaying body, assume the form and ar- 

 rangement of the matter dispersed. The change, 



a sponge". The water, with which the bituminated substance is 

 imbued, he supposes, in certain instances, to be saturated with 

 earthy particles, which are finally consolidated by crystallization, at 

 once infixing in the stony mass, thus formed, the undisturbed ar- 

 rangement of the enclosed vegetable fibres. Mr. Parkinson sup- 

 ports this theory by the fact, that every kind of petrified wood 

 yields, when submitted to chemical tests, traces of bituminized ve- 

 getable matter; and by observing, that the objections to the at- 

 tempt of accounting for the lapidification of vegetable substances, 

 by the process of substitution, are innumerable " In what man- 

 ner/' he asks, " can it be supposed, that a line, smaller than a 

 hair, extending from the centre of a piece of wood to its circum- 

 ference, can have its original component parts taken away, and 

 their places so exactly filled by earthy particles, merely deposited 

 by water, as to preserve its continuity unbroken 7" If, however, 

 this should be imagined to be possible, in the instance of a single 

 line, he will by no means admit it to be so, in the complicated sys- 

 tem of lines, which the innumerable minute vessels and fibres of 

 decayed wood present. ^Nor can we, he thinks, on the hypo- 

 thesis of substitution, account for the colour of the original being 

 so exactly retained, as it is in many specimens of petrified wood. 

 Without entering into any regular defence of the principles-we 

 have adopted, or a refutation of those advanced by Mr. Parkin- 

 son, it will perhaps be sufficient to remark, that the theory of sub- 

 stitution, by intromission^ does not necessarily require, as Mr. 

 Parkinson seems to think with Fourcroy, " the complete destruc- 

 tion of the original matter, and the disappearance of whatever con- 

 stituted its elements" this, indeed, can scarcely ever be the case ; 

 nor do we understand it to be absolutely contended for, by those 

 best informed on the subject. Bergman, on the contrary, ex- 

 pressly states, after describing the manner, in which stony matter 



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