OStT 
deposits. In proportion as the water aban- 
dons them, it penetrates the ligneous sub- 
stance, and destroys it insensibly. The 
woody fibres being decomposed, form in their 
turn voids and interstices, ar^cl there remains 
in the whole piece nothing but little stony cy- 
linders. But in proportion as these woody 
fibres disappear, the- surrounding moisture, 
loaded with earth in the state of dissolution, 
does not fail to penetrate the piece of wood, 
and to remain in its new cavities. The liew 
deposit assumes exactly the form of decom- 
posed libres ; it envelops in its turn the little 
cylinders which were formed in their cavities, 
and ends by incorporating with them. Vve 
may suppose here, that in proportion as it de- 
composes, there is a reaction of the ligneous 
part against- the lapidilic lluid: from this re- 
action a colour arises which stains more or 
Less the new deposit ; and this colour will 
make it easily distinguishable from that which 
lias been laid in the inside of the vessels. In 
all petrified wood this shade is generally per- 
ceptible. 
We have then, says M. Mongez, four dis- 
tinct epochs in the process by which nature 
converts a piece of wood into stone, or, to 
speak more justly, by which she substitutes-a 
stony deposit in its place: 1. Perfect vege- 
table wood, that is to say, wood composed of 
solid and of empty parts, of ligneous fibres, 
and of vessels Y. Wood having its vessels 
obstructed and choked up by an earthy de- 
posit, while its solid parts remain unaltered. 
3. The solid parts attacked and decomposed, 
forming new cavities betwixt the stony cy- 
linders, which remain in the same state, and 
which support the whole mass. 4. These 
new cavities tilled with new deposits, which 
incorporate with the cylinders, and compose 
nothing else but one general earthy mass, re- 
presenting exactly the piece of wood. 
Among the petrifactions of vegetables 
called deudrolites, are found parts of shrubs, 
stems, roots, portions of the trunk, some 
fruits, &c. We must not, however, confound 
the impressions of- mosses, ferns, and leaves, 
nor incrustrations, with petrifactions. 
Among the petrifactions of animals, we find 
shells, cfustaeeous animals, polyparii, some 
worms, the bony parts of fishes and of am- 
phibious animals, few or no real insects, 
rarely birds and quadrupeds, together with 
the bony portions of the human body. The 
cornua am monis are petrified serpents; and 
with regard to figured and accidental bodies, 
these are lusus naturae. 
In order, says M. Bertrand, in his Diction- 
naire des Fossil es, that a body should become 
petrified, it is necessary that it is, I. Capa- 
ble of preservation under ground. 2. That 
it is sheltered from the air and running wa- 
ter (the ruins of Herculaneum prove that bo- 
dies which have no connection with free air 
preserve themselves untouched and entire). 
3, That it is secured from corrosive exha- 
lations. 4. That it is in a place where there 
are vapours or liquids, Ibaded eithher with 
metallic or stony particles in a state of disso- 
lution-, and which, without destroying the 
body, penetrate it, impregnate it, and unite, 
with it in proportion as its parts are dissipated 
by evaporation. 
It is a question of great importance among 
naturalists, to know the time which nature 
employs in petrifying bodies of an ordinary 
PETRIFACTION, 
| size. It was the wish of the late emperor, 
1 duke of Lorraine, that some means should be 
taken for determining this question. M..je 
chevalier de Baillu, director of the cabinet of 
natural history of his imperial majesty, and 
some other naturalists, had, several years be- 
fore, the idea of making a research which 
might throw some light upon it. His impe- 
rial majesty being informed bv the unani- 
mous observations of modern historians and 
geographers, that certain pillars which are 
actually seen in the Danube in Gervia, near 
Belgrade, are remains of the bridge which 
Trajan constructed over that river, presumed 
that these pillars having been preserved for 
so many ages must be petrified, and that they 
would furnish some information with regard 
to the time which nature employs in chan- 
ging wood into stone. The emperor thinking 
this hope well founded, and wishing to satisfy 
his curiosity, ordered his ambassador at the 
court of Constantinople to ask permission to 
take up from the Danube one of the pillars 
of Trajan's bridge. The petition was granted, 
and one of the pillars was accordingly taken 
up; from which it appeared that the petri- 
faction had only advanced three-fourths of an 
inch i;* the space of 1300 years. There are, 
however, certain waters in which the trans- 
mutation is more readily accomplished. Pe- 
trifactions appear to lie formed more slowly 
in earths that are porous and in a slight de- 
gree moist than in water itself. 
When the foundations of the city of Que- 
bec in Canada were dug up, a petrified sa- 
vage was found among tire last beds to which 
they proceeded. Although there was no 
idea ot the time at which this man had been 
buried under the ruins, it is however true, 
that his quiver and arrows were still well pre- 
served. In digging a lead-mine in Derby- 
shire in 1744, a human skeleton was found 
among stags’ horns. It is impossible to say 
how many ages this carcase had lain there. 
In 1695 the entire skeleton of an elephant 
was dug up near Tonna,.iuThuriugia. Some 
time before this epoch the petrified skeleton 
of a crocodile was found in the mines of that 
country. We might cite another fact equally 
curious which happened at the beginning of 
the last century. John Munte, curate of 
Slsegarp in Scania, and several of his parish- 
ioners, wishing to procure turf from a drained 
marshy soil, found, some feet below ground, 
an entire cart with the skeletons of the horses 
and carter. It is presumed that there had 
formerly been a lake in that place, and that 
the carter attempting to pass over on the ice, 
had by that means probably perished. In 
fine, wood partly fossil, and partly coaly, has 
been found at a great depth, in the clay of 
which tile was made for the abbey of Fonte- 
nay. It is but very lately that fossil wood 
was discovered at the depth of 75 feet in a 
well betwixt Issi and Yauvres, near Paris. 
This wood was in sand betwixt a bed of clay 
and pyrites, and water was found four feet 
lower than the pyrites. M. de Laumont, in- 
spector-general of the mines, says that in the 
lead-mine at Pontpean, near Rennes, is a fis- 
sure, perhaps the only one of its kind. In 
that fissure, sea-shells, rounded pebbles, and 
an entire beech, have been found 240 feet 
deep. This beech was laid horizontally in 
the direction of the fissure. Its bark was 
converted into pyrites, the sap-wood into jet, 
and. tire centre into .coal. 
A great many' pieces of petrified wood are 
found in different counties of France and 
Savoy. In Cobourg in Saxony, and in the 
mountains of Misnia, trees of a considerable 
.thickness have been taken from the earth, 
which were entirely changed into a very line 
agate, as also their brandies and their roots. 
In sawing them, the annual circles of their 
growth have been distinguished. Pieces 
have been taken up, on whicli.it was distinct- 
ly seen that they had been gnawed by worms ; 
others bear visible marks of the hatchet. In, 
fine, pieces have been found which were pe- 
trified at one end,, while the other still re- 
mained in the state of wood lit for being 
burned. It appears then that petrified Wood 
is a great deal less rare in nature than is 
commonly imagined. 
Mr. Kirwan observes on the subject of pe- 
trifications, 1. Those of shells are found on or. 
near the surface of the earth ; those of fislv 
deeper; and those of wood deeper still. 
Shells in substance are found in vast quanti- 
ties, and gt considerable depths. 2 . The- 
substances most susceptible of petrifaction, 
are those which most resist the putrefactive-, 
process ; of which kind are shells, the harder, 
kinds of wood, &c. ; while the softer parts" of 
animals, which easily putrefy, are seldom met 
with in a petrified state. 3. They are most 
commonly found in strata of marl, chalk,. 
limestone, or clay; seldom in. sandstone, still 
more seldom in gypsum; and never in gneiss,, 
granite, basaltes, or schoerl. Sometimes 
they are found in pyrites, and .ores of iron, 
copper, and silver ; consisting almost always 
of that kind of earth or other mineral which 
surrounds them ; sometimes of silex, agate, 
or cornelian. 4. They are found in climates 
where the animals themselves could not have, 
existed. 5. Those found in slate or clay are - 
compressed and battened. 
The different species of petrifactions, ac- 
cording to Cronstedt, are, 
I. Terra larvatre ; extraneous bodies 
changed into a limy substance, or calcareous 
changes. These are, 1. Loose or friable: 
2.. Indurated. The former are of a chalky 
nature, in form of vegetables or animals ; the 
second filled with solid limestone in the same 
forms. Some are found entirely changed 
into a calcareous spar. 
On these petrifactions Cronstedt observes, 
that shells and corals are composed of limy 
matter even when still inhabited by their ani- 
mals, but they are classed among the petri- 
factions as soon as the calcareous particles 
have obtained a new arrangement: for ex- 
ample, when they have become sparry, filled 
with calcareous earth either hardened or 
loose, or when they lie in the strata of the 
earth. “ These (says he) form the greatest 
part of the fossil collections which are so in- 
dustriously made, often without any regard 
to the principal and only use they can be of, 
viz. that of enriching zoology. Mineralo- 
gists are satisfied with seeing the possibility of 
the changes the limestone undergoes in re- 
gard to its particles; and also with receiving 
some insight into the alteration which the 
earth has been subject to from the state of . 
the strata which are now found in it.” The 
calcined shells, where the petrifactions are of 
a limy or chalky nature, answer extremely 
well as a manure; but the indurated kind 
serve only for making grottoes. Gypseous • 
