MAR
Mar
mon in tables, &c. in the houfes of the polite part of the world. Hill's Hift. Foff. p. 481. Coralloide Marble, in natural hiftory, the name given by au- thors to fuch Marbles as have fpccimens of the marine corals or bodies of that kind immerfed in them, as the fca fhells are buried in, and make a part of the body of others. There are feveral fpecies of Marble fubject to hold thefe bo- dies but we have in England principally two in ufe, the one of a greyifh black, the other of a fine deep jetty black. The fiift is found in many parts of Derbyfhire, and the co- rals it contains are of the porus kind, and of one of the moft elegant fpecies in the world ; they are lodged in it at all an- gles, and in all directions, and are in general about an inch and half long, and three quarters of an inch broad, though fome are much larger, and others fmaller. They are com- \ pofed of longitudinal plates, very fine and thin, and of a mow white, ranged in diftinct orders, and finely interfperfed at fmall diftances, with thin tranfverfe plates ; the whole in- ternal part of the coral being thus divided into a fort of fquare cells. This net-like divifion runs through about three- fourths of the body, but the top has only the longitudinal plates without the tranfverfe ones. It is plain that thefe be- fore they were received into the bed of marble, had been fuftained in a fluid containing a very beautiful greyifh white fpar, for the net-like plexus of the bed is full of this matter ; but the open part at top having no plates for the retaining this matter, has remained empty till received into the Mar- ble, and is there found filled up with the common blackifh matter of the reft of the ftratum. It is an extremely beau- tiful fubftance when polifhed, and is ufed in many ornamen- tal works. It is found in many parts of Derbyfhire and in Wales.
The other, or black coralloide Marble, is alfo a very beauti- ful fpecies ; it is a very clofe compact fubftance, and of a fine even textuie, very hard, of a deep jetty black, and ca- pable of a high polim. It is elegantly variegated with fair and perfect fpecimens of a coralloide porus, approaching to the nature of the former, but fmaller and of a lefs elegant texture ; and among thefe has ufually a great number of fea fhells, both of the turbinated and bivalve kinds. Thefe are lodged in various directions, and all of them, the corals as well as the fhells, are of a pure mow white ; and as the matter and texture of the others plainly fhewed that they had been filled with fpar before they were immerfed into the bed of Marble ; thefe, on the other hand, retaining now no part of their original texture, though exactly their external fi- gure, but being all made up of the fame plain white fpar, plainly fhew that they were lodged in the Marble empty, and in their own native ftate ; for the cavities both of the corals and fhells are all nicely filled with the matter of the Marble j but they have now no coralline nor teftaceous mat- ter about them, but in tract of time have plainly perifhed, and the cavities they left in the hard and fmooth mafs of the Marble have been nicely and finely filled up with this fpar, which therefore now as perfectly reprefents their figures, as if themfclves were there. Hill s Hift. Fori", p. 473. It is found in great plenty in many parts of Ireland, particu- larly about Kilkenny, and is brought in great quantities to London, and ufed about chimney-pieces, and other oma-
■ mental works, and is commonly known among the artificers by the name of Kilkenny Marble.
Alabandhtm Marmor, a name given by the antients to a very remarkably glofly fpecies of black marble, dug near a city of that name in Caria, and much ufed in building among the Romans.
Caryjlium Marmor, a name given by the antients to a fpecies of marble, dug in the ifland of that name, and much ufed in ornamenting the public buildings ; it was of a beautiful green, deeper than the Tiberian and Auguftan marble, and without the white variegations. We meet with it fometimes among antlent remains ; and the Italian antiquaries particularly mean this, by a name alfo in ufe among us, and proftituted to every other fpecies of green marble, the verde aniiquo.
C/;;WMarmor. See the article Chium Marmor,
Fufile Marble. See the article Fusile Marble.
Marmor Hymcttium. See the article Hymettium Mar- mor.
Imitation of 'Marble inbrimftonc. Seethe articleBRiMSTONE.
Jajjenje Marmor. See the article Jassense Marmor.
Lychnitis Marmor. See the article Lychnitis Marmor.
Lydium Marmor. See the article Lydium Marmor.
Lygdinum Marmor. See the article Lygdinum Marmor.
Lumnfe Marmor. See thearticle Lunense Marmor.
Milium Marmor. See the article Melium Marmor.
Nunudicum Marmor. See thearticle Numidicum Mar- mor.
P*rium Marmor. See the article Parium Marmor.
Tbajium Marmor. See the article Thasium.
Tiberianum Marmor. See the article Tiberianum Mar- mor.
Derby Marble, among our artificers, a name given to a very beautiful fpecies of Marble, found in many parts of Derby- shire, and frequently worked into chimney-pieces in Lon-
It is a very lingular and beautiful fpecies j its conftituent mat- SupPL. Vol. II.
terisapale, fine, w&iftra brown Marble; of a fine clofe tex- ture, and very bright and glittering hue ; This is fo full of entrochi, that they make more than half the fubftance of the mafs ; and thefe cutting in different directions, and taking a fine polim, add greatly to the beauty Of the whole, when wrought. Hill's Hift. of Fofl". p. 479. The various forms in which thefe bodies appear in the ftone, when cut, might give a fufpicion that many of them were fome other foflile ; but this is only owing to their lying in all directions in the mafs ; but when nicely examined, the oddeft of them will be found to be no other than what a fingle com- mon entrochus may be cut into. They are of all fixes, front the thickhcls of a large pin, to half an inch or more. Italian Marble. See the article Italian Marble. Kilkenny Marble. See the article Coralloide Marele, fupra. Namur Marble. See the article Namur. Colouring of Marble. The colouring oi Marbles is a nice art, and in order to fucceed in it, the pieces of Marble, on which the experiments are tried, muft be well polifhed, and clear from the leaft fpot or vein. The harder the Marble is, the better it will bear the heat neceflary in the operation ; there- fore alabafter, and the common foft white Marble, are very improper to perform thefe operations upon. Heat is always neceflary for the opening the pores of the Mar- ble, fo as to render it fit to receive the colours ; but the Mar- ble muft never be made red hot, for then the texture of the Marble itfelf is injured, and the colours are burnt, and lofe their beauty. Too fmall a degree of heat is as bad as too great j for, in this cafe, though the Marble receive the co- lour, it will not be fixed in it, nor ftrike deep enough. Some colours will ftrike, even cold, but they are never fo well funk in as when a juft. degree of heat is ufed. The proper degree is that which, without making the Marble red, will make the liquor boil upon its furface. The menftruums ufed to ftrike in the colours, muft be varied according to the na- ture of the colour to be ufed. A lixivium made with horfe's or dog's urine, with four parts quick-lime, and one part pot- afhes, is excellent for fome colours ; common lye of wood- afhes does very well for others : For fome, fpirit of wine is beft; and finally, for others, oily liquors, or common white wine.
The colours which have been found to fucceed beft with the peculiar menftruums, are thefe : Stone blue diflblved in fix times the quantity of fpirit of wine, or of the urinous lixivium ; and that colour which the painters call litmoufe, diflblved in common lye of wood-afhes. An extract of faffron, and that colour made of buckthorn berries, and called by the painters, fap green, both fucceed well diflblved in urine and quick- lime, and tolerably well in fpirit of wine. Vermillion, and a fine powder of cochineal, fucceed alfo very well in the fame liquors. Dragons blood fucceeds very well in fpirit of wine, as does alio a tincture of logwood in the fame fpirit. Alkanet root gives a fine colour, but the only menftruum to be ufed for this is oil of turpentine ; for neither fpirit of wine, nor any lixivium, will do with it. There is another kind of 'fanguis draconis, called dragon's blood in tears, which, mixed with urine alone, gives a very elegant colour. Phil. Tranf. N°.268: Befide thefe mixtures of colours and menftruums, there are fome colours which are to be laid on dry and unmixed. Thefe are dragons blood, of the purefl: kind, for a red ; gamboge for a yellow, green wax for a green, common brimftone, pitch and turpentine for a brown colour. The Marble, for thefe experiments, muft be made confiderably hot, and then the colours are to be rubbed on dry in the lump. Some of thefe, colours, when once given, remain immutable, others are eafily changed or deftroyed. Thus the red colour given by dragons blood, or by a decoction of logwood, will be wholly taken away by oil of tartar, and the polifh of the Marble not hurt by it.
A fine gold colour is given in the following manner : Take crude fa] armoniac, vitriol and verdegreafe, of each equal quantities j white vitriol fucceeds beft, and all muft be tho- roughly mixed in fine powder.
The flaming of Marble to all the degrees of red, or yellow, by folutions of dragons blood or gamboge, may be done by reducing thefe gums to powder, and grinding them, with the fpirit of wine, in a glafs mortar ; but for fmaller attempts, no method is fo good as the mixing a little of either of thefe powders with fpirit of wine in a filver fpoon, and holding it over burning charcoal. By this means a fine tincture will be extracted, and with a pencil dipped in this, the fineft traces may be made on the Marble, while cold, which, on the heating it afterwards, either on fand, or in a baker's oven, will all fink very deep, and remain perfectly diftinct in the ftone. It is very eafy to make the ground colour of the Mar- ble red or yellow by this means, and leave white veins in it. This is to be done by covering the places where the whitenefs is to remain with fome white paint, or even with two or three doubles only of paper, either of which will pre- vent the colour from penetrating in that part. All the de- grees of red are to be given to Marble by means of this gum alone j a flight tincture of it, without the aftiftance of heat to the Marble, gives only a pale flefh colour, but the ftronger tinctures give it yet deeper ; to this the afiiftance of heat adds yet greatry ; and finally the addition of a little pitch to the E tincture
