254. This also explains some observations of Spallanzani, made in the island of Cerigo, on the coast of Greece, the Cythæra of the ancients.[135] The base of that island is limestone; but it abounds also in unstratified rocks, which the Italian naturalist supposes to be of volcanic origin; but which, if I mistake not, we would regard as whinstone, or perhaps porphyry; and they are said to contain oyster-shells and pectinites of a large size, perfectly mineralized. These petrifactions, however, Spallanzani says, are not contained in the lava that has actually flowed, but in stones which have only endured a slighter action of fire. Without the commentary afforded by the Portrush specimens, it would be difficult to make out any thing very precise from this description. By help of the information derived from those specimens, we may conclude, that the condition of the shells in them, and in the rocks of Cerigo, is perfectly alike; and that, in both cases, the shells are involved in parts of the rock which are truly stratified, but which have been, in some degree, assimilated to the basaltes by the heat which they have endured. Spallanzani would probably have used exactly the same terms which he employs in speaking of Cerigo, if he had been required to describe the petrified shells at Portrush. [Footnote 135: Journal de physique, tom. xlviii. (1798,) p. 278.] 255. In the instances just mentioned, the petrified marine objects are not found in the real whinstone; but if they were found in it, when it borders on stratified rocks containing such objects, the thing would not be at all surprising, nor furnish any argument against the igneous consolidation of the stone. If a torrent of melted matter was poured in among the strata, by a force which at the same time broke up and disordered those strata, nothing could be more natural, than that this matter should contain fragments of them, and of the objects peculiar to them.