the bones of Carnivora found beneath the stalactitic floors of caverns; or petrified by solutions of iron or other minerals, as are the remains of the extinct quadrupeds in many of the tertiary limestones, and those of the colossal reptiles in the Wealden deposits. They may also be invested with stalactite if buried in fissures or caves of limestone; or with travertine if exposed to the action of streams highly charged with carbonate of lime, like the so-called petrifying springs of Derby- shire; or impacted in ferruginous conglomerate, if deposited with implements of iron, or in a soil charged with chalybeate waters; and these effects may be produced in the course of a very brief period;—a few years, or even months, will often suffice for the formation of a compact, durable mass, in which bones, pottery, and coins, and other substances may be imbedded.
Although instances of such productions must be familiar to every antiquary, it may be instructive to notice a few examples that have come under my own observation, be- cause they serve to illustrate the nature and origin of certain specimens, which have been regarded by authors of deserved celebrity as genuine petrifactions, of immense antiquity. Thus the eminent mineralogist, Kirwan, quotes from Schneider's "Topog. Min."—" that one hundred and twenty-six silver coins were found enclosed in flints at Grinoe, in Denmark, and an iron nail in a flint at Potsdam."[1] The first edition of Mr. Bakewell's Introduction to Geology,[2] contains the following circumstantial narrative by Mr. Knight Spencer. "In 1791, two hundred yards north of the ramparts of Hamburgh, in a sandy soil, M. Liesky, of that city, picked up a flint, and, knocking it against another, broke it in two; in the centre of the fracture he observed an ancient brass pin; and on picking up the other half, he found the corresponding mould of the pin so laid bare, lie presented them to Thomas Blacker, Esq., in whose possession they now are, and who has shown them to the writer of this letter." In the "Gentleman's Magazine," and other periodicals, there are notices of similar discoveries of keys, nails, coins, &c. in flints and blocks of solid stone.
During my early attempts to investigate the geological structure of the South-East of England, I one day received a note from a South-Down farmer, informing me of the
