CARBONATE OF LIME.

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Cat cis Car'bonus.—Carbonate of Lime.

History. —Some varieties of carbonate of lime were distinguished andemployed in the most remote periods of antiquity. Marble was proba-bly used for building 1050 years before Christ (1 Chron. xxix. 2.)Pliny (Hist. Nat. xxxvi.) tells us that Dipcenus and Scyllis were re-nowned as statuaries of marble in the 50th Olympiad (i. e. 557 yearsbefore Christ.) The creta, mentioned by Horace (Sat. iii. lib. 2), andPliny (Hist. Nat. xxxvi. 58, Valp. ed.), was probably identical with ourchalk. (On the chalk of the ancients, consult Beckmann’s Hist, of In-vent. i. 212 )

Naturae History. —Carbonate of lime occurs in both kingdoms ofnature.

(a.) In the inorganized kingdom. —It forms a considerable portion ofthe known crust of the earth, and occurs in rocks of various ages. It isfound in the inferior stratified rocks, but more abundantly in the differentgroups of the fossiliferous rocks, particularly towards the central andhigher parts of the series (De la Beche , Researches in TheoreticalGeology, 21.)

In the crystallized form it constitutes calcareous spar and arragonite.The first of these is most extensively distributed, and presents itself undermany hundred varieties of shapes, the primitive form of all being therhombohedron.

Granular carbonate of lime (the granular limestone of mineralogists)more commonly occurs in beds, but sometimes constitutes entire moun-tains. The whitest and most esteemed primitive limestone is that calledstatuary marble, or, from its resemblance to white sugar, saccharoid car-bonate of lime. That from Carrara, on the eastern coast of the Gulf ofGenoa, is the kind usually employed by the statuary, and being verypure, may be employed for pharmaceutical purposes.

Chalk constitutes the newest of the secondary rocks, and occurs abun-dantly in the southern parts of England. It lies in beds, and containsabundance of marine as well as terrestrial organic remains. The upperpart of a considerable portion of the chalk of England contains nume-rous flints, which are supposed by some (Dr. Grant, Led. on Comp. Anat.in the Lancet, Nov. 2, 1833) to have once belonged to poriferousanimals.

There are various other native forms of carbonate of lime constitutingthe substances called by the mineralogist schiefer spar, rock milk, earthfoam, stalactitic carbonate of lime, anthraconite, oolite, pisolite, marl,tufa, &c.

Carbonate of lime is an ordinary ingredient in mineral and commonwaters, being held in solution by carbonic acid, and, therefore, depositedwhen this is expelled by boiling or otherwise.

(b.) In the organized kingdom .—Carbonate of lime is a constituent ofsome plants, and is obtained from the ashes of most. It is an abundantconstituent of animals, especially of the lower classes. Thus in theradiate animals we find it in the hard parts of corals, madrepores, &c.;in the molluscs, in the shells (as in the oyster). In the articulated ani-mals it forms, with phosphate of lime, the crusts which envelop these