PETRIFICATION is an operation of nature by which a body of the vegetable or animal kingdom is converted into stone while still preserving the form it previously had.

All stones are formed by the combination of earthy molecules which have been either dissolved or saturated with water: see the article Stones. It is therefore to water alone that petrification must be attributed; and so the question to examine is how this operation takes place. We shall take wood as an example, and consider how this substance, which has loose tissue when compared to stones, can turn into a hard, heavy, and compact body without losing any of its shape.

Wood, according to analyses, is composed of (1) soil that serves as its base, as for all bodies in nature; (2) a portion of water that enters into its composition; (3) a substance called extractive , which is either a gum or a resin, or both at the same time; (4) a saline substance which is sometimes of the nature of vitriol, sometime of niter, sometimes of sea salt. Wood is formed by the assemblage of a mass of threads or fibers which are so many tubes that give passage to the sap; it is filled with pores that go from the center to the circumference. When a piece of wood is buried in the soil, it soon starts absorbing water; this liquid, entering through its pores and fibers, slowly dissolves the substances which are soluble in it, such as the saline parts, the gummy parts, etc., and combines with the water that was already contained in the wood and was part of its composition. By this means, a decomposition of the wood takes place, its parts separating from each other; the pores and tubes dilate and swell, and water enters as into a sponge. Although it loses many of its components, the wood preserves its tissue and shape, and still has some of the soil that served as its basis. Indeed, when you burn a plant carefully, which is to say while protecting it from the wind, there remains an ash that is, so to speak, the plant’s skeleton; and this ash is nothing other than the soil and saline part of that very plant. Water, by constantly circulating in these empty fibers or tubes, deposits in them the earthy molecules which it itself contains; these molecules combine with those that entered into the composition of the wood, assume its shape, and fill it; and aided by evaporation, these accumulated molecules bond with each other, and the wood, changed to stone, preserves the same shape it formerly had. Then the wood becomes a mass of stone which is either limey or clayey, or of the nature of rock and agate, depending on the nature of the earthy molecules which the water has either dissolved or saturated, and has ferried and deposited in the wood fibers.

For this operation to take place, it is easy to understand that the soil in which the body to be petrified is contained be neither too dry nor too wet. Too much water would rot the wood too quickly and reduce it to soil before the molecules had time to arrange themselves gradually and bond with each other. On the other hand, too dry a terrain would not supply the water which, as we have seen, is absolutely necessary for petrification . The water must not be moving, because then it could not deposit the molecules it contains. Finally, the body to be petrified must be protected from the outside air, because its motion, if too violent, would disrupt the work of nature.

Some do not accept the existence of genuine petrification ; they seem to base their opinion on a dispute about words. It is quite certain that all the parts of wood are not converted to stone; only those that are earthy are able to enter into the new combination being produced. As for the other components, after being expelled they are replaced by the molecules deposited by the water: this replacement is what we call petrification . In this sense, it would be rather absurd to deny the existence of petrifications . Indeed, entire petrified trees, with their branches and roots have been found in several places on earth. When they were cut, the annual rings of their growth could be seen; there are pieces on which it can distinctly be seen that they had been host to worms; others bear visible signs of ax and saw. Finally, and this should silence incredulity, pieces of wood have been found, although rarely, of which a portion was still in the state of real wood that could burn, while another portion was changed to agate or some other kind of stone.

What we have just said about wood can apply to parts of animals that are petrified. Animals, like plants, have earth that serves as their base: it is this earth that forms their bones and shells; they further contain saline and aqueous parts; they are full of fibers and pores that can let the ground water in; in these pores and interstices of these animal substances this water can deposit the earthy molecules they carry, which can slowly harden. The animal substances which we most ordinarily find petrified are shells, madrepores, and fish bones: this is rather natural, insofar as those substances are already themselves quite analogous to stones, being composed for the most part of earthy and chalky molecules. With respect to the fatty and fleshy parts of animals, they are too loosely structured and too subject to rotting to allow time for water to deposit lapidific matter in their fibers.

As for petrifications of quadrupeds, they must be quite rare, if they even exist. Their bones are fairly often found buried in the earth, but that does not make them petrified; we must above all regard as very uncertain what has been reported by some writers about a petrified human body said to have been found in 1583 near Aix-en-Provence; the same can be said of the petrified men supposedly found in a mountain in Switzerland: these men, it is said, were part of the crew of a vessel that was found with its rigging in the same place. These events are as fictional as the supposed city of Bidoblo in Africa, of which we are told that all the inhabitants were petrified. [1] The marvel of this story will disappear if we observe that travelers who pass through the desert parts of Arabia and Libya are often suddenly buried under mountains of sand raised by the wind; their hardened and desiccated bodies are found several centuries later, which is what could have befallen the inhabitants of the city of Bidoblo.

A great many writers tell us of petrified bones of quadrupeds, yet on observing the thing closely one will find that nothing is less proven than their existence, and one will see that the bones of quadrupeds found in the earth are either in their natural state or simply eaten away and burnt. See the articles Fossil bones, Fossil ivory, etc. Yet it might be that these bones have, by the time spent underground, acquired much greater hardness than they had before, but that does not authorize including them among petrifications .

We also have reason to mistrust supposedly petrified birds with their eggs, which we are assured are found in the region of Hesse, in the Westerwald, in a mountain called Vogelsberg . We must make the same judgment concerning the petrified toads, lizards, and even snakes which have sometimes been found in the earth; as for serpents, there is reason to suspect that poorly educated persons could have been fooled by ammonites that look a lot like a coiled-up snake.

The fact is much more certain for marine animals, and we are assured that petrified ones are found. Near the villages of Mary and Lisy in the vicinity of Meaux, [2] large numbers of petrified crabs are found; in several other places palates and teeth of petrified fish, etc. are found, to the point of producing sparks when they are struck with a steel. Such are the kinds of stones called toadstones, shark teeth, etc. See those articles . Belemnites, ammonites, urchins or echinus, and a large number of shells and lithophytes are often genuinely petrified; some are found entirely transformed into rock or agate; others have served as molds for lapidific matter taken into the interior of those bodies. But it would be mistaken to place all marine bodies found buried in the earth among petrifications : some of these bodies have undergone no alteration, and others have simply been eaten away and lost their ligaments, which can look like a change into stone; whence we see that we must not indistinctly give the name petrification to all the shells or marine bodies deep in layers of earth. See the article Fossil. When we want to speak with precision, it would be important to distinguish even the stones that have molded themselves inside shells or marine bodies from true petrifications . Indeed, one often sees stones thus formed or molded still enveloped in the shell that served as mold for the lapidific material; the shell itself has not been changed, and is often in its natural state. Nor must we believe that the animal that lived in these shells has been converted into stone; all we can say is that stony liquor has come to occupy the place of the animal.

It would also be mistaken to take as a real petrification the incrustations or stony crusts that form around some substances that have spent some time in certain underwater places; the earthy molecules contained in these waters have been deposited on leaves or plants and covered them with a sort of coating that has hardened and changed to stone, while preserving the form of the body on which these molecules were deposited, whereas the body itself rotted and disappeared. See Incrustation.

Neither must we confuse with petrifications the imprints of plants or fish found on some stones; the stone that bears these imprints, when it was in a soft state, took on the shape of the body it surrounded, slowly hardened, and the body that made the imprint often has entirely disappeared.

See Phytoliths and Typolites.

Finally, the name of petrifications cannot be given to stones which chance circumstances underground have made to assume bizarre forms, which can sometimes have some resemblance to bodies extraneous to the mineral kingdom. See the article Freaks of nature.

Genuine petrifications are thus the animal or vegetable substances which have been infused and imbibed with stony liquor which has taken the place of the components which originally composed these bodies, without changing their structure or tissue. Countless examples prove to us that the earth holds petrifications of this type; they bear so distinctly the shape of the animal or vegetable body they originally were that it is impossible to mistake them. That is why we have so much petrified wood. In Franche-Comté, near Salins, a large quantity of walnuts and filberts were found entirely changed to stone. Chestnuts too have been found, pine cones, and other similar fruits genuinely petrified. But we have to admit that in amateur collections one often sees stones that are claimed to be petrifications and which really owe their shape to chance effects.

Some naturalists have been most curious to find out how much time nature took in petrification; they have believed that it could inform us on the antiquity of our globe. Emperor Francis I currently reigning, [3] whose interest in natural history is known to everyone, had a piling pulled from the Danube which had been used in a bridge which Trajan had had built on that river in Serbia. This piling was petrified all around to about the thickness of a finger. It appears that this means would be very unsure to help us discover the age of the world, seeing as certain waters bear more lapidific molecules than others, certain terrains can lend themselves better to petrification, and some substances can be more susceptible than others to receiving petrifying liquors; we have an example of this in the Irish lake named Lough neagh. See this article.

1. The seventeenth-century polymath Athanasius Kircher (1601-1680) discusses Bidoblo in vol. 2 of Mundus subterraneus (Amsterdam, 1668); Paul Lucas (1664–1737) describes another petrified town, Rassim, ou pays pétrifié , at three days’ distance from Ougella and ten from Bengazi, in Voyage du sieur Lucas fait par ordre du roy dans la Grèce, l’Asie Mineure, la Macédoine, et l’Afrique (Paris, 1712), vol. 2, pp. 124-26.

2. Mary-sur-Marne and Lizy-sur-Ourcq.

3. Francis Stephen (1708–1765), Holy Roman Emperor and husband of Maria Theresa of Austria.