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of those fine earthy particles, which have been merely suspended 
in the water. On the contrary, in, by far, the greater number of 
instances of vegetable petrifactions, the combination of both ope- 
rations is discoverable. 
In thus endeavouring to account for the formation of most of 
the endless variety of vegetable petrifactions ; which, from the 
wonderful appearances they display, and the circumstances under 
which they are found, are considered as, almost, anomalies in nature, 
I am aware, that the theory proposed, respecting the formation of 
bitumens, will be exposed to a severe test ; tried by such a touch- 
stone, the degree of estimation to which it is entitled can hardly 
fail of being determined. 
Although convinced of almost the universal agency of bitumini- 
zation, on such vegetable substances as have been rendered sub- 
jects of the mineral kingdom, yet it does not appear to be the 
sole process, by which vegetable matters may be preserved from 
total decay, a sufficient length of time, to admit of their slow 
impregnation with lapideous or metallic substances. The ligneous 
substance we have already seen, is of so indestructible a nature, as 
to secure its long continuance, in various situations, without under- 
going any material change of appearance ; even after the other con- 
stituent parts of the wood have been removed. This appears to be 
the state in which light rotten wood, or touch- wood, exists : all the 
constituent parts, excepting the ligneous substance, having been 
removed, either by the long continued action of the air, or by some 
morbid action of the vessels of the wood. If this species of wood, 
therefore, be placed in situations, in which water holding earth in 
solution can permeate it, there exists but little doubt that it may 
become petrified. Another mode by which the mineralization of 
vegetables may be secured, appears to be, that of decaying, but 
comparatively, recent vegetables, becoming impregnated by some 
saline, metallic solution, of iron, for instance, whilst a precipitated 
