Petrifactions. 
MINER 
2. Tantalium yttriatum, or yttrio-tantalite : confifting 
of oxyd of tantalium combined with the oxyds of iron 
find yttria. Found at Kimito in Finland, in fmall kid¬ 
ney-form mafies of inconfiderable hardnefs ; frafture gra¬ 
nular, iron-grey, of metallic luftre : may be fcratched with 
a knife, and gives a grey powder. Specific gravity, 5-13. 
Cerium. —Found maifive or difleminated ; luftre weakly 
glimmering; frafture fine-grained, even. Colour pale 
rofe-red, opake ; powder greyilh; fcratches glafs. Specific 
gravity, 4-5 to 4-9. Infuiible before the blowpipe, and 
does not colour borax. 
Cerium nativum, or cerite. This mineral has been 
found in the copper-mine of Baftnaes, at Riddarliytta in 
Sweden, accompanied by copper, molybdena, bilmuth, 
Utica, and hornblende. Conftituent parts ; 
Oxyd of cerium 
Vauquelin. 
67* 
Klaproth. 
54-'5 
■■■■■—>- iron 
- •oz 
4 ' 
Silex - 
34 ' 
Lime - 
- m o% 
. .. 
Water and carbonic acid 
- '12 
S' 
Lois ... 
15-84 
2 ’5 
IOOOO 
100*0 
The new metal contained in this mineral was difco- 
fered by Hinger and Berzelius, chemifts at Stockholm. 
CLASS V. PETRIFACTIONS, or FOSSILS. 
Fossil, in its ftri< 5 t and ufual fignification, is fynony- 
mous with mineral; being applied to the inorganic bodies 
that are formed in, and at the furface of, the earth, accord¬ 
ing to phylical and chemical laws. The French were the 
firlt who diftinguiflied by this appellation thofe animal and 
vegetable remains that, owing to particular circumftances, 
inftead of decaying when buried in the earth, have more 
or lefs preferved their original form and ftrudlure, and 
are found penetrated by, or even converted into, fub- 
ftances belonging to the mineral kingdom. Thefe fub- 
llances, before their natural hiftory began to be eluci¬ 
dated, were denominated lapides idiomorphi, figurati, dilu- 
wiani, See. but fuch names foon gave way to that of petri- 
fudla, or petrifactions, which was adopted in almoft all 
languages. In latter times, however, the denominations 
extraneous or adventitious fo(fils, propofed for this clafs of 
natural bodies by fir John Hill, have been revived by 
fome authors. Mr. Parkinfon, confidering the word petri¬ 
factions inadmiflible as a general term, recommends the 
appellation of fecondary foffils , while primary fojffils are to 
him thofe fubftances which are fuppofed to be natives of, 
and to have exifted primitively in, the fubterranean re¬ 
gions. Mr. Martin, in his Outlines, prefers the terms 
reliquium and reliquia, (which Ihould be reliquim .) Lin¬ 
naeus ufes larvata, “ malked,” a very expreftive word. 
But even thofe who reject the term petrifactions as not 
i'ufficiently general, retain another of the fame import in 
all the generic names of the extraneous foffils, fuch as 
ornitho/ithus, ichthyo/zf/uw, helminthofif//,«*, See. Other 
modern writers, again, have difeufled the fubjebl under 
the general term oryClognofy, or oryCtology; but, as thefe 
words are derived from the Greek o^vo-o-w, “ to dig,” they 
do not neceffarily lead the reader to petrifactions, but to 
any other fubftances dug out of the bowels of the earth. 
The word Petrifactions, therefore, which is adopted 
by Dr. Turton in his tranflation of the Syllema Naturae, 
feems to us the leaft obje&ionable defignation of the fub-- 
ftances it now remains for us to deferibe. 
If water impregnated with calcareous matter remains 
long in contact with extraneous fubftances, an earthy in¬ 
cruftation takes place, that foon excludes the incrufted 
fubftance from view ; which thus, in common language, 
is laid to be petrified: the ftiape, that is, remaining the 
fame; but the fubftance in appearance converted into 
ftone. In this manner are formed the well-known petri- 
fuftions of birds’-nelts, ntofs, leaves, &c. If the procefs 
Vol. XV. No. 1062. 
A L O G Y. Petrifactions, 5J7 
be carried on for a fufficient length of time, and the in¬ 
crufted body be of a perilhable nature, as in- the cafe of 
vegetable matter, the whole of this is removed by gradual 
decay, and the remaining mafs is entirely earthy: but its 
form, and the circumftances of its fituation, will generally 
ferve to (how its origin. 
Water, in penetrating through marble or limeftons 
ftrata, very commonly becomes impregnated in its paflage 
with particles of the calcareous carbonat; which it fub- 
fequently depofits, either by fimple expofure to air, or 
upon the furface of extraneous bodies with which it 
comes into contaft: in the firft inftance giving rife to 
thofe formations called Stala&ites, &c. in the lalt, to thofe 
earthy incruftations commonly called Petrifa&ions. The 
molt familiar inftance of the depolition of calcareous mat¬ 
ter from water is that which takes place on the inner 
furface of vell'els employed for the purpofe of boiling wa¬ 
ter impregnated with calcareous carbonat: it is called by 
Wallerius, Tophus calcareus lebetum; the term tophus 
arifingfrom its refemblance in lightnefs of texture to real 
tophi, or volcanic productions. A fimilar depofition takes 
place, at a common temperature, upon the furface of tubes 
and refervoirs conducting and holding the fame kind of 
water. The incruftation feparated from the fides of Car¬ 
fax-conduit, in Oxford, (at the time of its removal, about 
twenty-five years fince,) was nearly an inch in thicknefs ; 
and of a diltinCi fparry ftruCture. There is, in the Ox- 
lord Collection, part of a wooden duCt that ferved to 
convey the water from this conduit: the tranfverfe flec¬ 
tion of it is of a fquare form ; and it is worthy of obfer- 
vation, that the calcareous incruftation, which is of a ftra- 
tified appearance, is of equal thicknefs on every one of 
the four Surfaces : by which it appears, that a depofition 
of this kind is not merely mechanical; nor does it necef¬ 
farily follow, as fome have argued, that fuch depofitions 
accumulate according to the law of gravity: and hence 
there is no difficulty in fuppofing, that vertically-fituated 
veins may have been fometimes formed by lateral and 
fucceffive depofitions. 
The warm fprings of St. Philippe in Tufcany contain 
a great proportion of calcareous matter, which they de- 
pofit fo compaftly round fubftances immerfed in them 
as to be employed for the purpofe of obtaining calls, 
models, &c. With this view, hollow moulds being fuf- 
pended in the water, the earthy particles are depolifed in 
them ; and the depofition, when removed from the mould, 
prel’erves the exaft impreffion of it. Thefe incruftations 
are_ very delicately but very firmly compared ; and of a 
whitenefs equal to that of Carrara marble. It is faid 
that there are fprings of the lame kind near Guanca- 
Velica in Peru; and that many vafes and ftatues, See. are 
placed in the church of Lima, which have been formed 
from fuch depofitions. In a fimilar manner (as Kircher 
relates in his Mundus Subterraneus), the inhabitants of 
the neighbourhood of Tolfa incruft wooden models of 
crucifixes and candlefticks with cryftals of alum, by 
keeping them immerfed. for fome time in a folution of 
that fait; and with thefe they adorn their altars. 
Alonzo Barba gives an account of fome petrifying wa¬ 
ters of Peru, which greatly exceed all thofe we have in 
Europe in the quantity of ftony matter they contain. He 
tells us, that they foon choak up their own paflage bv 
the ftony matter they depofit there, and that all the cattle 
that drink of them die. He adds another ltory, which 
he probably took a little too haltily upon credit; viz. that 
they have moulds of the lhape of our bricks, which they 
fill with this water, and that, on being expoled to the 
fun a few days, the water is wholly converted into a ftone 
of the fame lhape ; and that they build their houfes and 
other edifices with thefe ftones. 
The fubftance called by the earlier mineralogical wri¬ 
ters ojleocolla, from its refemblance to a mafs of aggluti¬ 
nated bones, is nothing more than a calcareous depofition 
that has taken place round fmall branches and twigs of 
trees. In many inftances the vegetable fubftance has been 
6 Q. removed^ 
