PET 
387 
•PET 
petrifactions are extremely rare: however, 
Chardin informs us that lie had seen a lizard 
inclosed in a stone of that kind in Persia. 
II. Larvie, or bodies changed into a flinty 
substance. These are all indurated, and are 
of the following species: 1. Carnelians in 
form of shells from the river Tomm in Si- 
beria. 2. Agate in form of wood ; a piece of 
which is said to be in the collection of the 
■ count de Tessin. 3. Coralloids of white flint 
(millepora) found in Sweden. 4. Wood of 
•yellow flint found in Italy, in Turkey near 
Adrianople, and produced by the waters of 
Lough-neahin Ireland. 
III. - Larvae argillaceae; where the bodies 
appear to be changed into clay. These are 
found either loose and friable, or indurated. 
Of the former kind is a piece of porcelain 
clay met with in a certain collection, with all 
■ the" marks of the root of a tree upon it. Ot 
the latter kind is the osteocolla ; which is said 
to be the roots of the poplar-tree changed, 
and not to consist of any calcareous substance. 
A sort of fossil ivory, with all the properties 
of clay, is said likewise to be found in some 
places. 
IV. Larva: insalitae ; where the substances are 
impregnated with great quantities ot salts. 
Human bodies have been twice found impreg- 
nated with vitriol of iron in the mine ot Fail- 
le n, in the province of Dalarne in Sweden. 
One of them was kept for several years in a 
glass-case, but at last began to moulder and 
fall to pieces. Turf and roots ot trees are 
likewise found in water strongly impreg- 
nated with vitriol. They do not flame, but 
look like a coal in a strong fire; neither do 
they decay in the air. 
V. Bodies penetrated by mineral inflam- 
mable substances. 1. By pit-coal, such as 
wood; whence some have imagined coal to 
have been originally produced from wood. 
Some of these substances are fully saturated 
with the coaly matter; others not. Among 
the former Cronstedt reckons jet; among the 
latter the substance called mumia vegetable ; 
which is of a loose texture, resembling am- 
ber, and may be used as such. 2. r I hose pe- 
netrated by asphaltum or rock-oil. The only 
example of these given by our author is a 
kind of turf in the province of Skone in Swe- 
den. The Egyptian mummies, he observes, 
cannot have aiiy place among this species, as 
they are impregnated artificially with asplial- 
tuni, in a manner similar to what happens na- 
turally with the wood and coaly matter in the 
last species. 3. Those impregtlated With sul- 
phur which has dissolved iron, or with pyrites. 
Human bodies, bivalve and univalve shells, 
and insects, have been all found in this state; 
and the last are found in the alum state at 
Andrarum, in the province of Skone in Swe- 
den. 
VI. Larva? metalliferae ; • where the bodies 
are impregnated with metals, these are, 1. 
Covered w ith native silver; which is found on 
the surface of shells in England. 2. Where 
the metal is mineralised with copper and sul- 
phur. Of this kind is the fahlertz or grey 
silver-ore, in the shape of ears ot corn, and 
supposed to be vegetables, found in argilla- 
ceous slate at FrankenbergandTahlitteren in 
Ilesse. 3. Larva: cuprifene, where the bo- 
dies are impregnated with copper. 1 o tins 
species principally belong the turquoise or 
Turkey stones, improperly so called ; being 
| ivory and bones of the elephant, or other 
animals, impregnated with copper. At Si- 
more in Languedoc there are bones of ani- 
mals dug up, which, during calcination, as- 
sume a blue colour; but according to Cron- 
stedt, it is not probable that these owe their 
colour to copper. 3. With mineralised cop- 
per.. Of these our author gives two ex- 
amples. One is, where the copper is mine- 
ralised with sulphur and iron, forming a yel- 
low marcasitical ore. With this some shells 
are impregnated, which lie upon a bed of 
loadstone in Norway. Other petrifactions of 
this kind are found in the form of fish in dif- 
ferent parts of Germany. The other kind is 
where the copper is impregnated with sulphur 
and silver. Of this kind is the grey silver- 
ore, like ears of corn, found in the slate- 
quarries at Ilesse. 4. Larva: ferri ferae, with 
iron in form of a calx, which has assumed the 
place or shape of extraneous bodies. These 
are either loose or indurated. Of the loose 
kind are some roots of trees found at the 
lake Langelma in Finland. The indurated 
kinds are even exemplified in some wood 
found at Orbissan in Bohemia. 5. Where 
the'iron is mineralised, as in the pyritaceous 
larvie already described. 
VII. Where the bodies are tending to de- 
composition, or in a way' of destruction. 
Among these, our author enumerates mould 
and turf, &c. 
PETROCARYA, a genus of the class and 
order heptandria monogynia. The calyx 
five-cleft, turbinate ; corolla five-petalled ; 
filaments twenty-four ; drupe inclining, and 
two-celled nut. There are two species, trees 
of Guiana. 
PETROLEUM. See Bitumen. 
PETROMYZON, the lamprey, a genus 
of fishes belonging to the class of amphibia 
nautes. It has seven spiracula at the side of 
the neck, no gills, a fistula on the top of the 
head, and no breast or belly fins. There are 
eight species, distinguished by peculiarities 
in their back fins. 
1. The marinus, or sea-lamprey, is some- 
times found so large as to weigh four or five 
pounds. It greatly resembles the eel in 
shape, but its body is larger, and its snout 
longer, narrower, and sharper at the termi- 
nation. The opening of the throat is very- 
wide; each jaw is furnished with a single row 
of very small teeth ; in the middle of the pa- 
late are situated one or two other teeth, 
which are longer, stronger, and moveable to- 
wards the inside of the throat. 
The lamprey is an inhabitant of the ocean, 
ascending rivers chieily during the latter part 
of winter and the early months of spring ; and 
after a residence of a few months in fresh 
water, again returning to the sea: it is vivipa- 
rous, and the young are observed to be of 
slow growth ; contrary to the assertions of 
some writers, who have supposed the lam- 
prey to be a short-lived fish. When in mo- 
tion this fish is observed to swim with consi- 
derable vigour and rapidity, but it is more 
commonly sq,en attached by the mouth to 
some large stoueor other substance, the body 
hanging at rest, or obeying the motion of the 
current:' so strong is the power of adhesion 
exerted by this animal, that a stone of the 
weight of more than twelve pounds may be 
raised without forcing the fish to forego its 
hold. The general habits of the lamprey seem 
pretty much to aesemble those of the eel, and 
3 C 2 
PET 
it Is supposed to live principally cm worms 
and young fish Like the eel it is remarkably 
tenacious of life; the several parts, when cut 
in pieces, will long continue to move; and 
the head will strongly attach itself for several 
hours to a stone, though by far the greater 
part of the body is cut away from it. 
Among the cartilaginous fishes none is so 
destitute of all appearance of real bone as 
the lamprey-, in which the spine itself is no 
other than a mere soft cartilage, without any 
processes or protuberances whatsoever. 
Among other particulars in its anatomy, it is 
remarkable that the heart, instead of being 
inclosed in a soft pericardium, as in other 
animals, is guarded by a strong cartilaginous 
one: the liver, which is of an oblong form, is 
of a fine grass-green colour, somewhat deeper 
in the female fish, and may be used for the 
purpose of a pigment. 
A vulgar error, arising from inattentive 
inspection, and total ignorance of the nature 
of the animal, is said sometimes to prevail, 
viz. that the lamprey is furnished with nine 
eyes on each side ; this mistake appears to 
have excited unusual indignation in sir T. 
Brown. 
As an article of food, the lamprey has for 
many ages maintained its credit as an exqui- 
site dainty; and has uniformly m:<le its ap- 
pearance at the most splendid of our antient 
entertainments. The death ot king Ilenry 
the First, it is welt known, is attributed to a 
too luxurious indulgence in this his favorite 
dish. It still continues to be in high esteem ; 
and we are told by Mr. Pennant that the city 
of Gloucester continues to send yearly, at 
Christmas, a present of a rich lamprey-pie to 
the king. It sometimes happens that lam- 
preys at that season are so rare that a guinea is 
demanded for the price of a single fish. They 
are most in season during March, April, and 
May, and are observed to be much more 
firm when fresh-arrived from sea than when 
they have been a considerable time in fresh 
water. They are found in several of the 
British rivers, but that which is most cele- 
brated for them is the Severn. In the mouths 
of some of the larger European rivers they 
are sometimes taken in such quantities that 
it is impossible to use them in their fresh 
state ; they are therefore grilled and mode- 
rately salted, and afterwards barrelled up for 
sale, with the addition of vinegar and spices. 
2. Petromvzon fluviatilis, lampern. This 
species is, according to Dr. Bloch,- an inha- 
bitant of the sea, and ascends in spring-time 
most of the European rivers, in which it is 
found much more frequently and plentifully 
than the great lamprey. With us it is found 
in great quantities in the Thames, the Severn, 
and the Dee. It is often potted with the 
larger lamprey, and is by some preferred to 
it, as being milder-tasted. Mr. Pennant in- 
forms us that vast quantities are taken about 
Mortlake, and sold to the Dutch, as baits 
for their cod and turbot fisheries. Accoi ding 
to this author above four hundred and fifty 
thousand have been sold in a season, at fortv 
shillings per thousand, and about a hundred 
thousand have been occasionally sent to Har- 
wich for the same purpose. The Dutch, it 
is added, have the. secret of preserving them 
till the time of the turbot-fishery. Great 
quantities, says Dr. Bloch, are taken in the 
march of Brandenburgh, and in Pomerania, 
Silesia, and Prussia; and after frying, are 
