Various appellationshave been employ ed for the purpose of distinguishing these bodies from those minerals which do not owe their forms to animal or vegetable organization.
Figured stones (lapides ,figurati et idle morphu) and diluvian stones (lapidee dilu viani) were terms well chosen by the earlier mineralogists to designate these bodies, of the peculiar forms of which, and of their having probably obtained those forms from some changes depend ing on the deluge, they only could, with any propriety, speak. The term fossil tOinprising every mineral substance dug out of the earth, it was thought necessary to distinguish these by the term adventi tious or extraneous. To this generally adopted mode of distinction, Mr. Parkin son (Organic Remains, vol. i. p. 34,) ob jects.
The term extraneous, he observes, de notes that the substance spoken of is fo reign to the region in which it is found ; a sense in which, he thinks, it cannot, with propriety, be applied to such bo dies as are almost deprived, not only of their primitive form, but of their original constituent principles. In these cases, where so considerable a degree of na turalization, as it were, has taken place, the substance, lie conceives, can no long er merit an epithet implying their being foreign to the regions in which they are found. Instances of the impropriety of this employment of the term he instances in such of the jaspers and semiopals as have derived their origin from wood ; to which the epithet of extraneous does not appear to be strictly applicable. The term adventitious as implying the result of chance or accident, be thinks ought never to be applied to these substances ; since, in all nature's works, there exist not stronger proofs of the provident de sign of the Almighty Creator, than in the apparently casual disposition of these sub stances. To the term petrifaction be ob jects, because a conversion into stone on ly is here expressed ; whereas, in many instances, the substances of which the fossil is composed differs as much from stone, as from the matter of which the body was originally composed. Fossils he considers as of two kinds, primary and secondary ; among the former he places those bodies which appear to have been, ab initio, the natives of the subterranean regions and under the latter he disposes those substances, which, though now sub jects of the mineral kingdom, bear indu bitable marks of having been originally either of an animal or vegetable nature.
The term fossil, however, which implies that the organized substance under ex amination has been dug out of the earth, appears to be sufficient, without any ad junct to express these substances ; in deed this term is warranted to be thus employed by its general acceptation.
Besides those bodies which, being ac tually organic remains, deserve to be con sidered as fossils, (foseilia, vulgo dicta of Linmeus ;) other bodies require to be no ticed, as sometimes serving to illustrate the nature of organised fossils. These are, impressims, Citnpressa, Linnaeus ; tyfia• WM, Waller) ; Casts, (redintegrata, Lin nxus) ; and incrustations, (incrustata, Lin. nxus.) Fossils naturally divide into Vegetable and animal, according to which of those kingdoms they originally belonged; those of the vegetable kingdom shall be the first subjects of our inquiry.
The parts of vegetables confined in subterranean situations suffer, according to circumstances, either a complete reso lution of composition, the lighter parts be. coming volatilized, whilst the more fixed remain and form the substance which is termed mould (humus) ; or, as is sup posed by Mr. Parkinson, it passes through another process, which be considers as fermentative, and becomes bituminous. Wood, thus changed, is called lignum fossile bituminosum, surturbrand, and Bovey coal. By the extension of this process, the same author supposed, that the substances termed bitumens, (naph• tha, petroleum, and asphaltum), are form. ed. To the same process he also attri butes the formation of amber, of which however no proof appears. That jet, cannel coal, and the common coal em ployed in domestic uses, have had a vege. table origin, is rendered highly probable, from the frequency with which they mani fest the impressions of various vegetable bodies.