CAB, 



[71] 



CAB 



municates a dark colour : it forms 

 also regular beds of considerable 

 thickness, being the principal con- 

 stituent part of coal. Of Newcastle 

 caking coal it constitutes 75-28 per 

 cent., of cannel coal 64' 72 per cent. 

 The carbon in the atmosphere is 

 not considerable, but without it 

 vegetation could not exist. Saus- 

 sure ascertained that 10,000 parts 

 of atmospheric air contained, as a 

 mean, 4.9 of carbonic acid. Com- 

 bined with oxygen, carbon forms 

 carbonic acid or fixed air. 



CA'RBONATE. A combination of car- 

 bonic acid with a base. Carbonic 

 acid is capable of combining with 

 earths, oxides, and alkalies, and 

 to these combinations the term 

 carbonate has been applied ; thus 

 we have the carbonate of lime, 

 carbonate of magnesia, carbonate of 

 lead, carbonate of iron, carbonate 

 of ammonia, &c., &c., &c. 



CA'RBONATE OF LIME. A union of 

 carbonic acid and lime, consisting 

 of 57 parts of lime and 43 of 

 carbonic acid. The form of the 

 integrant molecule of carbonate of 

 lime was decided by the Abbe 

 Haiiy to be an obtuse rhomboid. 

 This conclusion was implicitly 

 adopted by mineralogists, till the 

 Count de Bournon announced the 

 discovery of cleavages passing 

 through the long diagonal of its 

 rhomboidal faces, and maintained 

 that the form of its integrant 

 molecule was a trihedral prism with 

 inclined bases. Dr. Brewster has 

 since satisfactorily proved that the 

 cleavages obtained by Co ant Bour- 

 non exist only in those specimens 

 which are crossed by interrupting 

 veins, and therefore that the tri- 

 hedral prism is not, but that the 

 obtuse rhomboid is the form of the 

 integrant molecule of carbonate of 

 lime. Carbonate of lime, under 

 the several names of chalk, lime- 

 stone, marble, &c., is found most 

 abundantly throughout nature. All 



limestones effervesce when a drop 

 of strong acid is thrown on them, 

 and they entirely dissolve in nitric 

 or muriatic acid. 



It is a difficult problem, says 

 Professor Buckland, to account for 

 the source of the enormous masses 

 of carbonate of lime that compose 

 nearly one eigth part of the super- 

 ficial crust of the globe ; some have 

 referred it entirely to the secretions 

 of marine animals ; an origin to 

 which we must obviously refer 

 those portions of calcareous strata 

 which are composed of comminuted 

 shells and corallines ; but until it 

 can be shown that these animals 

 have the power of forming lime 

 from other elements, we must 

 suppose that they derived it from 

 the sea, either directly, or through 

 the medium of its plants. [The 

 presence of carbonate of lime in a 

 rock may always be ascertained by 

 applying to the surface a drop of 

 diluted sulphuric, muriatic, or 

 nitric acids : the lime having a 

 stronger affinity for any one of 

 these than for the carbonic acid, 

 unites itself immediately with 

 them, and the carbonic acid being 

 liberated escapes in a gaseous form, 

 frothing up or effervescing as it 

 makes its way in small bubbles.] 

 CARBONIFEROUS GROUP. | Thecarboni- 

 CA'RBONIFEROUS SERIES, j ferous group 

 or series comprises the coal mea- 

 sures, the mountain or carboniferous 

 limestone, and the old red sand- 

 stone. The rocks of this group, says 

 Sir C. Lyell, consist of limestone, 

 shale, sandstone and conglomerate ; 

 interstratified with which are large 

 beds of coal. Several hundred 

 species of plants have been found 

 in the shales and limestones associ- 

 ated with the coal, all of which 

 are, with few exceptions, of species 

 differing widely from those which 

 mark the vegetation of other eras. 

 It is in this formation chiefly, that 

 the remains of plants of a former 



