Page:Proceedings of the Royal Society of London Vol 1.djvu/179

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Among the several spontaneous permutations in the productions of nature, none perhaps are more striking, and in many cases more unaccountable, than those which transfer bodies from one kingdom of nature into another: and those changes which transform organized into fossil substances are certainly not the least extraordinary and instructive.

The most numerous instances of this transformation are, no doubt, what we distinguish by the name of Eatraneous Fossils; some of which still retain part of their original substance, whilst others can only be regarded as casts or impressions. An attentive observer will soon perceive a kind of gradation in these fossils, whether from ani- mals or vegetables, commencing with those whose matter retains a marked analogy with that of the recent substances, and terminating in bodies decidedly mineral. And a curious remark occurs here,— that as animal petrifactions are most commonly of a calcareous nature, so, on the contrary, vegetable petrifactions are generally siliceous.

Without entering any further into a general disquisition on this important subject, our author proposes to discuss, 'in this paper, one particular case of the changes which organized, and especially vege. table, substances undergo, by being long buried in earthy strata, and thus exposed to the effects of mineral agents : and the instance he selects is the bituminous substances, concerning which he has long suspected that they are derived from the organized kingdoms, and especially from the resin and juices of vegetable substances, by the action of some of the mineral principles.

He cites three instances in this kingdom in which nature points out these changes, and which exhibit the gradations above intimated. These are,—l. The submarine forest at Sutton, on the coast of Lin- colnshire, the timber of which has not suffered any very apparent change in its vegetable characters; 2. The strata of bituminous wood (called Bovey Coal) found at Bovey, iu Devonshire, which exhibit a series of gradations, from the most perfect ligneous texture to a sub- stance nearly approaching to the characters of pit-coal; and 3. All the varieties of pit-coal, so abundant in many parts of this country, in which almost every appearance of vegetable origin has been ob- literated.

As the Bovey coal appears to be the mean in that gradation, and therefore most likely to afford instructive results, our author resolved to limit his inquiry into this process of nature, which may not improperly be called Carbonization, to that fossil, and to a peculiar bituminous substance with which it is often accompanied. But here he ﬁnds it expedient to premise some observations on a remarkable