CALCAREOUS EARTH. 
CALCAREOUS EARTH. Hither carbonate 
of lime in nearly a pure state, or an earthy mix- 
ture of which it is one of the ingredients. Cal- 
cium is a simple or elementary body, of a metal- 
lic nature, nowhere naturally existing in a se- 
parate condition, and artificially obtainable only 
in small quantities and by a difficult process. 
Lime or quicklime is an oxide of calcium, and is 
usually obtained by expelling carbonic acid from 
rocky or earthy bodies containing carbonate of 
lime in large proportion. Carbonate of lime is 
the chief ingredient in chalks, limestones, and 
several kinds of marls and spars, and exists in 
| nearly a pure state in such limestones as consti- 
_ tute the finest sorts of statuary marble; and this 
substance, whether as constituting lithological 
| strata in portions of the globe’s crust, or as 
crushed to powder and intermixed with other 
substances in the forms of diluvium and alluvium, 
_ is what mineralogists and scientific agriculturists 
designate calcareous earth. 
Some soils naturally contain such large pro- 
_ portions of calcareous matter as to be themselves 
_ properly and characteristically designated cal- 
| careous; some contain it in sufficient proportion 
_ for the purposes of fertility, either by natural 
| intermixture of limestone debris, chalk, shells, 
or marl, or by artificial commixations and man- 
urings of quicklime; and others are nearly or 
wholly destitute of it, and consist principally or 
wholly of argillaceous, siliceous, or hypnotic 
| matter. 
The adding of calcareous earth, in the 
form of either top-dressing or incorporated man- 
ure, to the first of these classes of soils, would, 
in most cases, be sheer poisoning; the adding of 
it to the second class must, in all cases, be regu- 
lated by the niceties of judicious husbandry ; and 
the adding of it to the third is, in almost every 
case, essential to the extraction from them of re- 
munerating or even meagre crops. 
All the calcareous earths, when burnt or cal- 
- cined, become friable, and fall into a white pow- 
der ; they evolve strong heat, and fall more or 
less readily into powder, if, after being calcined, 
they are drenched with water; they cannot by 
themselves be vitrified in a close fire; they aug- 
ment, in their burnt state, the causticity of pot- 
ash ; and they exhibit powerful alkalinity by 
free and copious effervescence in acids, — Cal- 
careous earth exists nearly pure, in the form of a 
powder, in moors, at the bottom of lakes, and in 
the fissures of sandstone quarries, in Oxfordshire, 
Northamptonshire, and some parts of Sweden. 
This powder is sometimes called lac lune, it is 
supposed to be the debris of limestone rock, pul- 
verized by the motion of water; it has a white 
colour in England, and a colour varying to yel- 
low and red in Sweden; but it occurs in too 
small quantities to admit of application to the 
uses of agriculture.—Calcareous earth occurs both 
friable and compact in the form of chalk; yet, 
when in this form, it always contains some ad- 
mixture of other earths, and a very large propor- 
CALCEOLARIA. 619 
tion of carbonic acid. White chalk is the least 
impure of the chalks; and yet it contains some 
silica, and about two per cent. of argillaceous 
earth.—Calcareous earth occurs in a gravelly 
form in limestone gravel, and in a compact and 
indurated form in limestone rock. Yet, in this 
form, it always contains some proportion, and 
sometimes a very large proportion of siliceous 
and argillaceous earths. Some limestones, also, 
as the dolomites, have magnesium and not cal- 
cium for their ultimate base, and may prove 
very unsuitable or even poisonous succedanea 
for calcareous manure.—An earth of calcium, 
though not properly a calcareous earth, occurs in 
the form of gypsum or plaster of Paris. This 
substance is a combination of lime and sulphuric 
acid, while marble, chalk, or any other true cal- 
careous earth, is a combination of lime and car- 
bonic acid ; and it does not effervesce with acids, 
and, when calcined to powder, concretes and 
hardens under the subsequent action of water ; i 
yet though so different, in at once chemical con- 
stitution, alkalinity, and mechanical property 
from a true calcareous earth, it readily contri- 
butes its base of lime as a manure, and merits 
full consideration in the treatment of soils which | 
require to be dosed with calcareous matter.— 
Calcareous and argillaceous earths occur com- 
binedly in the form of marls; but they exist in 
such widely different proportions as to have oc- 
casioned a loose general classification of marls 
into shell marls and clay marls. All true marls 
effervesce with acids,—and the strongly calcare- 
ous proportionably more than the weakly cal- 
careous; yet some pure clays, when in a dry 
state, evolve a quantity of air under the mere 
action of water, as well as under the action of a 
liquid acid, and have in consequence been mis- 
taken for marls. Highly calcareous marl con- 
sists principally of the shells of aquatic animals, 
and is often so entirely free from clayey matter 
as to be very strictly a calcareous earth. See 
the articles Limr, Cuatx, Gypsum, Maru, and | 
Sols. 
CALCEOLARIA. A genus of herbaceous and | 
shrubby ornamental plants, of the figwort tribe. 
It first became known in Britain so late as the 
year 1773; it did not become known, in any of 
its finer or more beautiful species, till the year 
1822; it did not evoke for itself, from either 
amateur or professional florists, a fixed or nor- 
mal law of beauty, till about 1828; it did not | 
produce any decidedly good English hybrids till — 
about 1830; and yet it already fills whole green- | 
houses in the public nurseries,—it boasts an al- — 
most innumerable multitude of brilliant and 
most fascinating hybrids,—it figures most con- 
spicuously in even the smallest collections of | 
tolerably good flowering plants,—and it possesses 
so enthusiastic favour and such a lofty fashion- 
ableness, that one-half of all the unscientific 
flower-fanciers of our country appear, for the 
present, to have gone calceolaria-mad. We have 
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