Marble, a rock used as an ornamental building stone, for interior decorations, and for sculpture. Generally, any limestone that can be obtained in large sound blocks, and is susceptible of a good polish, is marble; and the only marble that is not limestone is the serpentine and the oriental verde antique (the latter a mixture of serpentine and limestone). It is found in beds in various geological formations. In the azoic group it is a metamorphic rock of granular and crystalline structure, and often presents a fineness of texture and purity of shading that tit it for the choicest works of the sculptor. In the palaeozoic formations it bears more of the character of a sedimentary rock, and it is apt to contain organic vestiges, as corallines and fossil shells, which indeed sometimes compose nearly its whole substance; it is also of variegated colors, and sometimes is of brecciated structure, evidently made up of fragments of an older rock, the layers of which, broken up and confusedly rearranged, have been cemented together. Though thus varying greatly in color, texture, and structure, the composition of marble is for the most part essentially the same; it is a carbonate of lime, or a combined carbonate of lime and carbonate of magnesia, and is readily burned to quicklime.

It is soft and easy to work with the chisel or hammer, generally of even grain, so as to be split with wedges, and of specific gravity about 27. making the weight of a cubic foot about 169 lbs. its durability is very variable, some varieties retaining sharp edges when exposed for many years to the weather, and others soon crumbling away. - Many varieties of marble have acquired a name and celebrity from remote times. The ease with which the rock is worked caused it to be selected for the earliest structured The names of many marbles famous among the ancient Greeks and Romans are still retained, and their localities are known. Mt. Pentelicus in Attica furnished the valuable Pentelican white marble, called by the moderns Penteli marble; the islands of Paros and Naxos, the still celebrated Parian marble; and other similar white marbles came from Mt. Hymettus in Attica, from Thasos and Lesbos, from Corallus in Phrygia, from Cyzicus on the Propontis, and one variety, exceeding the Parian in whiteness, from Luna in Etruria. Of the first named (the Pentelican) the Parthenon was built, and also the temple of Ceres at Eleusis, besides many celebrated statues. Though of finer grain than the Parian, it is said not to retain its polish and beauty so well.

The Parian marble is plaeed first by both Theophrastus and Pliny in their enumeration of ancient marbles. Pindar and Theocritus also celebrated its praise. The statues of Venus de' Medici, Diana Venatrix, the Oxford marbles known as the Parian chronicle, and many other famous works, are of this marble. Black marbles are occasionally referred to by the ancients; but some of those named, as the Chium marmor from the island of Chios, appear to be of questionable character. This one is sometimes called lapis obmdianous antiquorum. It was glossy black, and received so high a polish that it was made mirrors. The green marbles were serpentines from various localities. Yellow marble was obtained at Corinth. The marmor Phengitesot Cappadocia was white with vel-low spots; the Rhodian was marked with gold-en-colored spots, and that of Melos (Milo) was yellow. - The marbles of modern times have been variously classified and named. In southern Europe two general divisions are made of antique and modern. The quarries of the former being lost or abandoned, the stone is obtained only from ancient monuments; and being consequently most highly prized, methods are resorted to, and sometimes with success, to attach the name antique to stone from quarries now worked.

It is also the case that some of the marbles held in the highest estimation in France, being transported from monuments at Rome, are the product of quarries worked in ancient times in France. It is probable these might be again discovered. Without reference to these marbles, however, the French boast that their country surpasses even Italy in the beauty and variety of this class of stones. - The following are convenient divisions in which marbles may be arranged for a general notice of the most important of them: 1, the simple or single-colored marbles; 2, the variegated; 3, the brecciated; 4, the lumachella or fossiliferous. These sorts, however, pass into each other, so that some may be placed indifferently either in one or the other of two groups. 1. The best known of the first class are the plain white marbles, some of which have been already named. The white marble of Carrara, of which an account is given in the article Caeeaea Maeble, is of a texture like loaf sugar, differing in this respect from the Parian marble, which on close examination appears to be made up of the most delicate plates or scales, confusedly but most closely united together. Pure black marble is found in some ancient Roman sculptures.

Some varieties of it are obtained in Derbyshire, England, and in Kilkenny, Ireland; but as the latter is more or less intermixed with fossil shells, it should come under the fourth division. It is quarried in the United States at Shoreham, Vt., and Glen's Falls, N. Y., and specimens are obtained from some other localities. The colored marbles are generally variegated; but the Siena marble of Italy is sometimes of a uniform yellow color, or the same clouded. Some of the red marbles of Italy also display only the one color. In North America white marbles are worked at various places on the range of the great belt of metamorphic rocks through Canada, Vermont, western Massachusetts, a little hack of the cities of New York, Philadelphia, Baltimore, and Washington, and thence through Virginia and the Carolinas into northern Georgia and Alabama. It is this formation that supplies the white marble for building purposes to the different cities along its range, and its quarries in Massachusetts and New York furnish the marble for the most costly edifices of southern cities. The statuary marble is only the finest grained variety of this common building stone. Many localities are known to furnish it in small beds interstratified with the coarser marble.

Sev-eral quarries of fine statuary marble have been opened in Vermont. The first were at Rutland, but other localities have since been found. Excellent quarries are also found in other parts of the United States. 2. The variegated marbles are those variously spotted, shaded, and veined. They are the most numerous class, and include the most beautiful of the colored marbles. None are more highly esteemed than the variegated yellow marble of Siena. This and the Italian dark red marbles may be seen in many of the costly mantels in our marble shops; and also the soft, shaded, dove-colored Lisbon marble, of which are made the smaller columns in the entrance of the Unitarian church at the corner of 4th avenue and 20th street, New York. The black Genoese marble, with golden-colored and white veins, called Portoro marble, the best of which is from Porto Ve-nese, has for many years past been the most popular and the best known foreign marble in all parts of the United States, though now rather out of fashion. It is a weak stone, and is for the most part used in thin slabs cemented upon a back of slate.

The marbles of this class found in the United States east of the Rocky mountains have not attained much celebrity, nor do we know of any worthy of it, unless we should include among them certain varieties of the brecciated marbles from northern Vermont and Tennessee. The gray and white clouded limestones of Thomaston, Me., are quarried to considerable extent for marble, and may be seen in common use in portions of the eastern states. They possess little beauty. California has furnished of this class some very showy marble of brilliant reddish and brownish colors, and susceptible of a high polish. It is imported into New York and used for mantels. 3. The brecciated marbles are composed of angular fragments, it may be of various mineral substances, united in a bed or paste of calcareous cement; or the mass may be so divided by numerous veins into pieces as to present the appearance of broken fragments irregularly united. Brocatellas are breccias, in which the fragments are very small; we incorrectly apply the name only to a reddish brecciated marble brought to this country from Spain. The varieties of this class are very numerous; but some of the most celebrated are never seen here, such as those called le grand deuil and le petit deuil, literally the full mourning and the half mourning.

These come from the Pyrenees and different parts of France; they are of a black ground spotted with white fragments. Among the brecciated marbles of the United States, the best known is that of the Potomac on the Maryland side, some miles below the Point of Rocks. The principal use that has been made of it was to furnish the columns in the old chamber of representatives at Washington. The irregularities of hardness in the different ingredients render it an expensive stone to work; still the quarries are deserving of more than government patronage. The stone is certainly handsomer than the Italian red and white breccia imported for the inner columns of the central arched entrance of the church before mentioned. Quarries have been opened in the northern part of Vermont, near Lake Champlain, which produce the most beautiful of the American colored marbles. They are brecciated, though they pass into the variegated. They present a great variety of colors, from a deep red, traversed with veins of white, to rose-tinted flesh color mottled with whitish spots. In some specimens the brecciated structure is very strongly marked, the fragments being large with sharp edges and of decided shades of dark red, drab, and salmon, upon a ground of white bordered with rose.

Unlike the Potomac marble, the fragment- are not different varieties of rock, but are all limestone. The stone, though somewhat hard for marble, is still of uniform texture and takes an even high polish. Some large blocks closely resemble the foreign brocatella. It is however very difficult to work. Other marbles of this character and of rather dark red colors abound near Knoxville, Tenn., and have been brought into notice by the extent to which they are employed in the construction of the capitol at Washington. 4. Lumachella or fossiferous marbles are those which contain petrified shells. These are sometimes so crowded upon one another, that they compose the whole mass of the stone; sometimes single shells are seen scattered throughout the block. These marbles are very abundant in Europe, and also throughout New York and the western states. Handsome mantels are made of American varieties which are composed entirely of fossil shells, but they are rather to be regarded as curious than beautiful. They lack the high colors of the brecciated and variegated marbles, and though they take a good polish, they are from their plain colors comparatively dull and sombre.

Some of the best of the kind is from Becraft's mountain, back of Hudson, N. Y., which is thus noticed by Prof. Silliman ("American Journal of Science," vol. vi.. p. 371): " The marble is of a grayish color with a slight blush of red; its structure is semi-ci talline, and in some places highly crystalline, especially in and around the organized bodies which in vast numbers it embraces. The large slabs present a great diversity of appearance, and can scarcely be distinguished from the similar transition marble of the Peak of Derbyshire, which it quite equals in beauty and firmness." - Serpentine, as before stated, differs in composition from the other marbles. It consists of about equal parts of silica and magnesia with 12 per cent, of water. It is a soft mineral of different shades of green, of waxy lustre, and susceptible of a high polish. It is better adapted to ornamental work within doors than to be exposed to the action of the weather. Verd antique is a mixture of green serpentine and light-colored limestone. These varieties come from Genoa and lus-canv, and the best verd antique from Egypt. In Vermont and Canada serpentine abounds; and verd antique may be obtained in various places in New York and Pennsylvania, and in anv of the New England states.

At Milford, Conn., a quarry of serpentine and verd antique was worked more than 50 years ago, which furnished slabs pronounced by good judges quite as fine as the European stone. - The methods of preparing marble for use differ from the working of granite. This hard rock, after being quarried, is split by small wedges driven into holes drilled in a line, and is then dressed by hammers or used in the rough. Marble, being a comparatively soft rock, is cut into slabs by a process of sawing with smooth iron saws fed "with sharp sand and water. Several of these plates or saws are set in one frame, and in a large establishment 20 or more of the frames may be seen kept in steady operation by a steam engine. The progress of the saws cutting down through the great blocks of marble seems very slow, for the most part not exceeding an inch per hour. The thickness of the slabs is usually four or six inches. In this form the marble is used for facing the walls of buildings upon a back of brick, giving all the effect of a solid wall of marble at much reduced cost. In the most expensive structures only are the walls built of solid blocks of marble or freestone.

Marble slabs for mantels and other interior work are sawed like those for building, and are then rubbed smooth upon a heavy revolving table of cast iron, called the rubbing bed, and afterward polished. - According to the census of 1870, there were 22 marble quarries in operation in the United States, employing a capital of $1,316,000. The total products amounted to $804,300. The most extensive quarries were in Maryland, where the products for the year were valued at $275,000; New York, $222,000; Vermont, $130,800; Pennsylvania, $101,000; and Massachusetts, $59,500 Marble valued at $3,709,518 was worked into monuments and tombstones, valued at $8,916,654. The value of marble and stone and manufactures thereof, imported into the United States during the year ending June 30, 1873, was $1,099,280, of which $423,818 was from Italy.