448 Earths. Ml NERALqGY. Earths. 
cining in the fire, but not vitrifying in the ftrongeft heat. 
There are ten fpecies. 
1. Creta conchacea, or /hell-lime: containing fniall 
and very minute /hells; not cohering, not foiling the 
fingers, without lu/lre. Found in the maritime parts of 
Etruria, Saxony, and Wirtemberg; rarely covered with 
moujd. 
2. Creta granulata, or granular lime : confifting of 
rounded, quite-glabrous, milk-white, opake, granula¬ 
tions, which do not /lain the fingers. Found on the 
fhores of Afcenlion I/land, between Africa and Brafil ; 
where it ferves as a nidus for the Teftudo Mydas to lay 
its eggs in. It is compofed of /hells and corals commi¬ 
nuted by the waves of the tea, or of the harder calcareous 
fubftances worn down and rubbed together by the torrents 
of river's. 
3. Creta te/tacea, or teftaceous lime : produced by com¬ 
minuted /hells ; without lullre, not flaming the fingers. 
Found on the coafts of England and France. 
4. Creta pulverulenta, or native lime: reducible to 
dull 5 without luflre, rough to the touch, ftaining the fin¬ 
gers. Found near Bath ; white, without luflre or tranf- 
parency; fradlure earthy, and ea/ily rubs to powder; 
when mixed with a little oxyd of iron, it becomes yel- 
lowilh. 
Lime has the property of combining with fome of the 
other earths and metallic oxyds, forming mortar of dif¬ 
ferent qualities. Dr. Higgins, in his book upon cements, 
propofed the following as the bell cornpofition for com¬ 
mon mortar : Three parts of fine wafhed land, four parts 
of coarfer land, one part of newly-flacked lime, made up 
with as little water as poflible, which he recommends to 
be foft water. Mortar, thus formed, becomes very hard 
in a little time, and continues to become harder for a great 
length of time. Hence has arifen the miftake, of the an¬ 
cients being in fome fecret of making mortar, which is 
not known to the moderns. 
A great improvement has lately been made in making- 
cements by combining lime with oxyd of iron and manga- 
nefe. An iron ore abounding with clay, a calcareous mat¬ 
ter, and pyrites, have been introduced under the name of 
Parker's cement, from the name of the inventor and pa¬ 
tentee. After burning and grinding to powder,it has the 
property of fetting rapidly when mixed with water, and 
even under water. This rapid induration can be ex¬ 
plained only by luppofinga great affinity to exift between 
the different earths and metallic oxyds in its cornpofition. 
See CiEMENTUM in this article; and the word Mortar, 
where various kind of mortars, cements, and ftucco, will 
be delcribed. 
Among other great and ufeful properties of lime, the 
following is not the leaft. Moll coal-mines are interrupt¬ 
ed by what the colliers term damp, which is only an ex¬ 
cels of hydrogen gas, that often takes fire from the lighted 
candles attempted to be introduced into the work ; the 
damp then burns with a blue flame, and explofions enfue, 
and very often the miners at work and the winders at the 
mouth cf the pit fall vidlims. In this fituation nothing 
further need be done, but to flack half a bulhel or a bulhel 
of lime frefli burnt, in the level or pallage made by the 
miners in digging out the coals; the carbonic acid of 
which will correct the air in the works, and make it fa¬ 
vourable to inhalation and combuftion, and the miners 
will be able to proceed in their work. The prevalence 
of the damp in coal-mines is fo general, and its effetts fo 
dangerous by privation of lives, that the fuccefs of apply¬ 
ing a certain and cheap remedy could not be too gene¬ 
rally known, though other remedies have been lately in¬ 
vented, of which we lhall have occafion to fpeak in a fu¬ 
ture article. 
5. Creta fquamofa, or fcaly lime: with fomewhat-greafy 
white lliining leales, which foil the fingers. Found near 
Gera in Italy. Very friable, falling to dull in water; ad¬ 
heres to the tongue, and is entirely loluble in nitrous acid. 
Colour fometimes filvery-white. 
6 . Creta farinaceh, or agaric-mineral: farinaceous, 
loofely cohering, floating, foiling the fingers. Found in 
various parts of Europe, in the clefts of rocks, or the 
bottom of lakes, or in calcareous mountains. It is ex¬ 
ceedingly brittle, and reducible to duft; does not adhere 
to the tongue. Colour white, reddilh, or yellowilh. 
7. Creta icriptoria, or common chalk : folid, rough, 
flightly adhering to the tongue, without luflre, opake, 
ftaining the fingers, breaking into indeterminate frag¬ 
ments. Common chalk is found in large ftrata in various 
parts of Britain, Germany, France, and Sweden, particu¬ 
larly on fome fea-coafts ; often containing flints, and the 
veftiges of echini and /hells. Colour generally white, 
rarely greyilh ; feels rather rough to the touch, and effer- 
velces ftrongly with acids. Contains carbonat of lime 95, 
alumine 3, water 3. For its medical ules, fee Chalk, 
vol. iv. p. 75. 
8. Creta argentea, Schaum-eartli, or filvery chalk. 
Found in the cavities of limeftone in Thuringia and the 
north of Ireland. It has a light yellowilh, and nearly a 
lilver-white, colour. It occurs both in mafles and diffe- 
minated, and alfo in fine fcaly particles. The luflre is 
lliining, fometimes inclining to femi-metallic and pearly. 
The fracture is curvedly foliated ; the fragments blunt- 
edged. It is opaque, foft, and friable. Its conftituent 
parts, according to Bucholz, are, lime, 51-5 ; carbonic 
acid, 39; lilex, 5-7; iron, 3-3 ; water, 1. 
9. Creta ganil, or arenaceous limeftone : folid, hardilh, 
brittle, a little lliining, and tranfparent. This is found 
on the lliores of Rhaghety, a fmall illand on the coaft of 
Antrim, and at Codrilla, on the weft fide of Vefuvius ; 
yellowilh-white. In the lump it cannot be eafily broken, 
but in fmall pieces it fritters between the fingers ; phof- 
phorefees when fcraped in the dark with a knife. Specific 
gravity, a'742 : contains carbonic acid 47. Kirwan. 
10. Creta madreporata, or madrepore-ftone. This rare 
fubftance was difcovered by baron Moll in the valley of 
Rulsbach, in the territory of Saltzburg. Externally, and 
on its longitudinal frafture, its colour is greyilh-black; 
on the crofs-frafture, it is of a pitchy-black colour. It 
has been found hitherto only in maflive, blunt-cornered, 
rounded, and oblong, fometimes flattened, pieces, of from 
three inches to one foot in diameter. Its furface is more 
or lefs finely furrowed, and fometimes fmall /hallow holes 
are feen in it; furrows often radiating, and marked with 
tranfverfe minute ftriae. Externally this fubftance is glim¬ 
mering, palling into dull; internally, on the longitudinal 
frafture, partly glimmering, partly gliftening; but on the 
tranfverfal planes of frafture it Ihows a pitchy luflre, fome¬ 
times approaching to metallic. It gives a grey ftreak. It 
is not particularly hard; it is brittle, and eafily frangible. 
Fragments opaque, indeterminately angular, not very 
fliarp-edged, always of a ftraight or divergingly-columnar 
ftrubture : they often contain copper pyrites, finely dif- 
feminated, and in pellicles. Before the blow-pipe, the 
black colour of the madrepore-ftone is converted into 
greyilh-white. 
According to the analyfis of Meflrs. Schrol and Heim, 
the conftituent parts of this fubftance are, lime 63 T 4 -r, 
alumine 10^, filex 12^, iron 15^-f; and the fame con- 
ftituents, and their proportion, are quoted in the French 
fyllems of mineralogy, as the refuit of an analyfis of 
madreporite made in the Ecole des Mines. But Klaproth, 
who analyfed a fpecimen lent by baron Moll himfelf, ob¬ 
tained the following refults: Carbonat of lime, 93 ; car¬ 
bonat of magnefia, 0-50; carbonat of iron, 1-25 ; carbon 
(radical), 0-50; arenaceous filex, 4-50; and a very fmall 
portion of oxyd of manganefe. The ftrufture of the fe- 
parate pieces of fliis mineral, refembling the aggregation 
of madrepores, has given rife to its name. Some mi- 
neralogifts have, indeed, luppofed that the fubftance 
derives its origin from a fpecies of madrepore; but 
Klaproth oblerves, that this opinion is not fupported 
by any certain mark indicative of preceding organic 
ftruriure. 
Magnesiata, 
