MAEBLE 217 



The bird's-eye maple is the American variety, the best being obtained from Prince 

 Edward's Island. The mottled maple is a commoner variety. 



MARBLE. This title embraces such of the primary, transition, and purer com- 

 pact limestones of the secondary formation, as may be quarried in solid blocks without 

 fissures, and are susceptible of a fine polished surface. The finer the white, the more 

 beautifully variegated the colours of the stone, the more valuable, c&teris paribua, is 

 the marble. Its general characters are the following : 



Marble effervesces with acids ; affords quicklime by calcination ; has a conchoidal 

 scaly fracture ; is translucent only on the very edges ; is easily scratched by the knife ; 

 has a spec. grav. of 2'7 ; admits of being sawn into slabs ; and receives a brilliant 

 polish. These qualities occur united in only three principal varieties of limestone : 



1, in the saccharoid limestone, so called from its fine granular texture resembling that 

 of loaf-sugar, and which constitutes modern statuary marble, like that of Carrara ; 



2, in the foliated limestone, consisting of a multitude of small facets formed of little 

 crystalline plates applied to one another in every possible direction, constituting the 

 antique statuary marble, like that of Paros ; 3, in many of the Devonian and Carboni- 

 ferous, or encrinitic limestones, which occur below the coal formation. 



The saccharoid and lamellar, or statuary marbles, belong entirely to metamorphic 

 districts. The greater part of the close-grained coloured marbles belong also to the 

 same geological localities ; and become so rare in the more recent limestone forma- 

 tions, that immense tracts of these occur without a single bed sufficiently entire 

 and compact to constitute a workable marble. The limestone lying between the 

 Great Oolite and the Cornbrash of the lower oolite, and which is called 'Forest 

 marble ' in England, being susceptible of a tolerable polish, and variegated with im- 

 bedded shells, has sometimes been worked into ornamental slabs in Oxfordshire, 

 where it occurs in the neighbourhood of Wychwood forest ; but this case can hardly 

 be considered as an exception to the general rule. Even higher in the geological 

 series, marbles may occasionally be worked ; thus the Purbeck and Wealden series 

 yield shelly bands of freshwater limestone, which, under the names of Purbeck marble, 

 Sussex marble, &c., have been largely used for the clustered shafts in Gothic archi- 

 tecture. 



To constitute a profitable marble-quarry, there must be a large extent of homogeneous 

 limestone, and a facility of transporting the blocks after they are dug. On examining 

 these natural advantages of the beds of Carrara marble, we may readily iinderstand 

 how the statuary marbles discovered in the Pyrenees, Savoy, Corsica, &c. have never 

 been able to come into competition with it in the market. In fact, the two sides of 

 the valley of Carrara may be regarded as mountains of statuary marble of the finest 

 quality. 



The various tints of ornamental marbles generally proceed from oxides of iron ; but 

 the blue and green tints are sometimes caused by minute particles of hornblende, as 

 in the slate-blue variety called Turchino, and in some green marbles of Germany. 

 The black marbles are coloured by carbon, mixed occasionally with sulphur and 

 bitumen ; when they constitute ' stinkstone.' 



Brard divides marbles, according to their localities, into classes, each of which con- 

 tains eight subdivisions : 



1. Uni-coloured marbles ; including only the white and the black. 



2. Variegated marbles ; those with irregular spots or veins. 



3. Madreporic marbles, presenting animal remains in the shape of white or grey 

 spots, with regularly disposed dots and stars in the centre. 



4. Shell marbles ; with only a few shells interspersed in the calcareous base. 



5. Lumachella marbles, entirely composed of shells. 



6. Cipolin marbles, containing veins of greenish talc. 



7. Breccia marbles, formed of a number of angular fragments of different marbles, 

 united by a common cement. 



8. Pudding-stone marbles ; a conglomerate of rsunded pieces. 



Antique marbles. The most remarkable of these are the following : Parian 

 marble, called Lychnites by the ancients, because its quarries were worked by lamps; 

 it has a yellowish-white colour, and a texture composed of fine crystalline facets, lying 

 in all directions. The celebrated Arundelian marbles at Oxford consist of Parian 

 marble, as does also the Medicean Venus. Pentelic marble, from Mount Penteles, near 

 Athens, resembles the Pari-in ; but is somewhat denser and finer grained, with occa- 

 sional greenish zones produced by greenish talc, whence it is called by the Italians 

 Cipilino statuario. The Parthenon, Propyloeum, the Hippodrome, and other principal 

 monuments of Athens, were of Pentelic marble ; of which fine specimens may be seen 

 among the Elgin collection, in the British Museum. Mar/no Greco, or Greek white 

 marble, is of a very lively snow-white colour, rather harder than the preceding, and 

 susceptible of a very fine polish. Jt was obtained from several islands of the Archi- 



