The mineral, vegetable, and animal kingdoms, respectively contribute to supply the substances which are necessary in the arts. Of these substances, many have been known and used from the time of the earliest records; others are of recent introduction, and additions are still making to the stock previously known. The value of a substance to the arts, may be estimated from the importance of the object it fulfils, its durability, the number of purposes to which it may be applied, and the facility with which it is convertible to use.

MATERIALS FROM THE MINERAL KINGDOM.

STONES AND EARTHS.----Marble,--The class of stones denominated calcareous, is exceedingly numerous and abundant in nature. Of these, marble is the most important. It is a granular carbonate of lime, varying in color, texture, and hardness Marble is extensively used for building, statuary, decorations, and inscriptions. In warm countries, it is one of the most durable of substances, as is proved by the edifices of Athens, which have retained their polish for more than two thousand years. Severe frost, preceded by moisture, causes it to crack and scale. Great heat reduces it to quicklime. Marble is wrought by chiselling, and by sawing with smooth plates of iron, with sand and water. It is polished by rubbing with sand and water, and afterwards with putty and soft substances.

Numerous stones of the calcareous class, more or less approaching to marble in their character, have been converted to use in different countries. The pyramids of Egypt are built of a grayish white calcareous stone, enclosing shells. The Parthenon, and other structures of Athens, are of Pentelic marble, distinguished by slight greenish veins. The mosques of Constantinople are of a fine-grained limestone from Pappenheim, the same which is now used in lithography. At Rome, a porous whitish limestone, called tophus by the ancients, and travertino by the moderns, is the material of the Colosseum, of St. Peter's church, &c. The ruins of Paestum are of a stone nearly similar. The building called the Tomb of Theodoric, at Ravenna, has a dome consisting of a single stone, which is thirty-four feet in diameter. It is a gray limestone from Istria, and is computed to have weighed, when taken from the quarry, more than two million pounds. Paris is built with calcareous stone, of which there are five kinds. The Portland stone, of which St. Paul's and other edifices in London are constructed, is a calcareous rock called Oolite by mineralogists. Specimens of marble abound in the United States, and are seen in the City Hall of New York, the United States and Pennsylvania Banks, Philadelphia, the Washington Monument, Baltimore, &c. The columns of the Girard college, in Philadelphia, were obtained from the quarries in Sheffield, Berkshire county, Massachusetts.

In statuary, the Venus de Medicis, and Diana venatrix, are formed of Parian marble. The Apollo de Belvidere, according to Dolomieu, is made of Luni marble; and if so, must be posterior to the time of Julius Caesar, before which period that quarry was not opened.

Granite.--Granite is apparently the oldest and the deepest of rocks. It is one of the hardest and most durable which have been wrought, and is obtained in larger pieces than any other rock. Granite is a compound stone, varying in color and coarseness. It consists of three constituent parts; viz., quartz, the material of rock crystal; feldspar, which gives its colors, and which is the material of porcelain earth; and lastly mica, a transparent, thin, or foliated substance, which affords a flexible substitute for glass, when obtained in large pieces. Granite is chiefly used for building. It is split from the quarries by rows of iron wedges driven simultaneously in the direction of the intended fissure. This method is thought by Brard to have been known to the ancient Romans and Egyptians The blocks are afterwards hewn to a plane surface by strokes of a sharp-edged hammer. Granite is also chiselled into capitals and decorative objects; but this operation is difficult, owing to its hardness and brittleness. It is polished by long-continued friction, with sand and emery.

The largest mass of granite, known to have been transported in modern times, is the pedestal of the equestrian statue of Peter the Great, at St. Petersburgh. It is computed to weigh three million pounds, and was transported nine leagues by rolling it on cannon balls. Those of cast iron being crushed, others of bronze were substituted. Sixty granite columns at St. Petersburgh consist each of a single stone twenty feet high. The columns in the portico of the Pantheon at Rome, which are thirty-six feet eight inches high, are also of granite. The shaft of Pompey's Pillar, so called,[A] in Egypt, is sixty-three feet in height, and of a single piece. It is

said to be of red granite, but is possibly sienite. In the eastern part of the United States, a beautiful white granite is found in various places, and is now introduced in building. The new market-house in Boston, the United States Bank, &c., are made of it.

[A] The inscription on this pillar is said by the Earl of Mountnorria, in Brande's Journal, to belong to Dioclesian, and not to Pompey, as was formerly supposed.

Sienite.--This rock is related to granite, and resembles it in its general characters. It consists chiefly of feldspar and hornblende. Sienite is obtained in large pieces, and possesses all the valuable properties of granite; but being harder, it is somewhat more difficult to chisel. It is found in Egypt, and constitutes the material of many of the obelisks. The Romans imported it from that country. Sienite is found abundantly near Boston, and is introduced into many structures. The Washington Bank, the Court-house, the Bunker Hill Monument, and the Astor House in New York, consist entirely of this stone. Its extreme hardness renders it one of the best materials for McAdam roads. A railway is built at Quincy for transporting the stone from the quarry to the sea, and the name of Quincy stone is now commonly applied to it.

Freestone.--Freestone consists of sand, or silicious particles, united by a cement. It is also called sandstone. It varies in color, from grayish white to red and. dark brown. It is of moderate hardness, in general, and easily wrought by the chisel. Varieties of freestone are used in building, in different parts of Europe. In Africa, the temple of Hermopolis is composed of enormous masses of this stone. In America, the Capitol, at Washington is of the Potomac freestone, likewise the facade of St. Paul's church, in Boston. This stone is used for various other practical purposes, particularly the grinding of steel instruments, and the filtering of water.

Slate.--Slates are valuable for the property of splitting, in one direction, so as to afford large fragments which are perfectly flat and thin. The best slates are those which are even, compact, and sonorous; and which absorb the least water on being immersed. Slates are much used as an incombustible covering for the roofs of houses. Tablets, gravestones, and writing slates, are also formed from them.[A]

Mica.--Mica, which has been already mentioned, is a finely foliated, elastic substance, transparent when obtained in thin layers. It is used for lanterns, and is inserted in the doors of stoves to show the state of the fire. It becomes opaque when exposed to much heat. It is sometimes cut into feathers and other ornaments, and affords a flexible substitute for glass.

Mica Slate.--This slate is well known by its brilliant silvery lustre. It splits into tablets, which are obtained of the diameter of eight or ten feet. It is chiefly used for the flagging stones of sidewalks. It is apt to crumble at the corners, and is too friable to bear the attrition of carriage wheels.

Soapstone.--This stone is usually of a grayish color, moderately soft, and having an unctuous feel, which is compared to that of soap. It is remarkable for bearing heat, and sudden changes of temperature, without injury. It receives a tolerable polish. Soapstone, on account of its softness, is wrought with the same tools as wood. It is sometimes used in building, but is not always durable. It is, however, of great importance in the construction of fireplaces and stoves, and is extensively used for this purpose. Slabs of good soapstone, when not exposed to mechanical injury, frequently last eight or ten years, under the influence of a common fire on one side, and of cold air on the other. It grows harder in the fire, but does not readily crack, nor change its dimensions sufficiently to affect its usefulness. Owing to the facility with which it is wrought, its joints may be made sufficiently tight without dependence on cement. Among the best quarries for fire-proof stone, is that of Francestown, New Hampshire. Soapstone is manufactured into various vessels and utensils, and is advantageously employed for aqueducts. Pumps are sometimes made of it. It is found to be one of the best materials for counteracting friction in machinery, for which purpose it is used in powder mixed with oil. A hard species of soap-stone, from Reading, in Massachusetts, has lately been introduced into building.

[A] Various artificial compositions have been employed as substitutes for slate, in forming water-proof coverings for roofs. One of these, which appears to have been successfully used in the north of Europe, is formed of bolar earth, chalk, glue, pulp of paper, and linseed oil.--Franklin Journal, iv. 89.

Serpentine.--Serpentine is a smooth, compact stone, more or less of a greenish color, composed chiefly of magnesia and silex. It is sufficiently soft to be scratched with a knife, and receives a polish like that of marble. It is used in building, in Florence and other parts of Italy, and in Saxony it is wrought into many small articles of ornament.

Gypsum.--Gypsum, called in commerce plaster of Paris, is a sulphate of lime, of which there are many varieties. When dried by heat, ground to fine powder, and mixed with water, it has the property of becoming hard in a few minutes, and of receiving accurately the impression of the most delicate moulds. It is extensively employed for stucco working, and plastering of rooms. It furnishes a delicate, white, and smooth material for casts of statues, architectural models, impressions of seals, &c. In the art of stereotyping, it is indispensable. It is used in agriculture to fertilize certain soils.

Alabaster.--Under this name, two substances are known in commerce. One is a carbonate of lime, deposited by the dripping of water in stalactitic caves. The other, and the most common, is a compact gypsum. This is softer than marble, translucent, and susceptible of a fine polish. Many beautiful ornaments, such as vases, statues, shades for lights, &c, are made from it. As alabaster of the last species is soluble in five hundred parts of water, Mr. Moore has proposed an easy method of cleansing it, by immersing it for about ten minutes in water, and afterwards rubbing it with a brush dipped in dry, powdered plaster.

Chalk.--Chalk is a soft carbonate of lime, the properties of which are well known. It is used as the basis of various white pigments, and cementing substances. Common whiting is purified chalk, prepared by reducing the chalk to fine powder and agitating it with water. The sand and coarser particles first subside, after which the water is drawn off and the whiting suffered to deposit itself. Chalk, by calcination, furnishes excellent lime.

Fluor Spar.--This is a fluate of lime. The variety chiefly used is the Derbyshire spar, which is beautifully variegated with purple and other colors. Ornamental objects and utensils are made from it. Its acid, when disengaged, is sometimes used to corrode glass.

Flint.--Flint is found in roundish masses, and is composed almost wholly of silex. Its extreme hardness causes it to strike fire readily with steel, from which property its greatest use is derived. Gun-flints are formed by practised workmen, who break them out with a hammer, a roller, and steel chisel, with small repeated blows. Flints are used also in the manufactures of glass, porcelain, and Wedgewood's ware. For this purpose, they are reduced to fine powder by heating red hot, and plunging them in water; afterwards by pounding, sifting, and washing. Flints are broken up to form McAdam roads.

Porphyry.--Porphyry is a variegated stone, consisting of small crystals of feldspar or quartz, imbedded in a basis of a darker color. It receives a beautiful polish, but its extreme hardness renders it difficult to work. The ancients made columns and even statues of this material; but the moderns confine its use chiefly to smaller works, such as vases, boxes, mortars, &c.

Buhrstone.--This is a hard, silicious stone, remarkable for its cellular structure; containing always a greater or less number of irregular cavities. Hence its surface, however worn and levelled, is always rough. This property renders buhrstone an invaluable material for mill-stones. When it is not found of sufficient size for this use, small pieces of it are fitted together, cemented, and bound with an iron hoop. It is imported from France, and is also found in some localities in the United States.

Novaculite.--This stone is commonly known under the names of hone, Turkey oilstone, &c. It is of a slaty structure, and owes its power of whetting or sharpening steel instruments, to the fine silicious particles which it contains. Various other stones are used as whetstones, such as common slate, mica slate, freestone, &c.

Precious Stones.--These are better known as objects of luxury, than of use; yet their preparation gives rise to an extensive branch of industry. They are in general distinguished for their small size, and great brilliancy, permanency, and hardness. The latter quality renders them useful in the arts. The diamond is generally employed for cutting sheets of glass. The diamond, ruby, sapphire, and some others, are used by watchmakers for pivot holes to diminish the friction of their verges and axles. These stones are wrought by grinding them with emery and other hard powders. The diamond can only be cut with its own dust. Various hard, silicious stones of less value, as the carnelian, jasper, agate, &c, are used by lapidaries for engraving seals, cameos, and other objects of ornament.

Emery.--The best emery is a variety of the corundum stone, obtained chiefly from the island of Naxos, in the Archipelago. Several other substances, however, are sold under this name. Emery is the hardest of all known substances, except the diamond, and its powder is extensively used in grinding and polishing metals, stones, and glass. It is reduced to powder by grinding it in a steel mill, and is afterwards assorted into parcels of different fineness, by agitating it with water, and separating the particles which deposit themselves at different times; the finest articles being the last which subside.

Sand.--Sand of the best quality, is that which consists of particles of pure quartz, and such only is used in the manufacture of fine glass. It is found in various localities; but is most commonly procured, in this country, from the banks of the Delaware. Impure sand answers only for bottles and inferior glass. For mechanical purposes, such as grinding glass and marble, sharp sand, the particles of which are angular, is best. The sand used for moulds, by brass-founders, possesses a somewhat argillaceous character, sufficient to render it moderately cohesive when wet, in consequence of which quality it retains its shape. The sand used in mortar should be sharp, and free from all perishable or deliquescent ingredients.

Pumice.--This is a spongy, porous stone, of a fibrous texture, and so light as often to swim in water. It is considered to be of volcanic origin. It is employed to grind the surface of metals, and other minerals. On account of its lightness, it is sometimes used to construct domes, vaults, and other elevated parts of buildings. The dome of the mosque of St. Sophia, at Constantinople, is said to be of this material.

Tufa.--This name is applied to a number of volcanic productions, some of which are aggregates of sand, ashes, and fragments of scoria and lava, united by a cement. The tufa which is found about Rome, is of a reddish color, and is supposed to be the lapides rubri of Vitruvius. Its surface is easily decomposed by the atmosphere, yet some of the ancient Roman temples and aqueducts are built of it, and among others, the temple of Fortuna virilis.

Peperino.--The lapis albanus of the ancients, now called peperino, appears to be a kind of tufa, or concretion of volcanic ashes, but somewhat more solid and durable than the other kinds. It is the material of some of the ancient Roman structures, and is found in the forum of Nerva and the temple of Antoninus and Faustina.

Tripoli.--This mineral resembles certain clays, but is rough and friable, and does not form a paste with water. It possesses a fine hard grit, and is used to polish metals and stones. Common rotten stone and polishing slate are varieties of tripoli.

Clay.--This abundant and useful earth is composed principally of alumine and silex. It possesses the valuable property of forming, when wet, a ductile and tenacious paste, which is changed by heat to a stony hardness. Common clay, of which bricks and coarse potter's ware are made, contains oxide of iron, which causes it to turn red in burning. The purer sorts, such as pipe clay, become whiter when exposed to a high heat. The earthy smell, which clays emit when breathed upon, appears also to be owing to oxide of iron. Absolutely pure clays emit no smell. Refractory clays are those which endure the greatest heat without melting. The best fire-proof bricks and crucibles are made from slate clay, and contain a good deal of sand. Sometimes they are made of old materials, which have been before exposed to high heat, pounded up and mixed with fresh clay. A mixture of two parts of Stourbridge clay and one part of coke, has been found very refractory.

Asbestos.--Asbestos is a mineral of a fibrous structure. One of its varieties, called Amianthus, is composed of very delicate, flexible filaments, resembling fibres of silk. It has been manufactured into cloth and paper, which possess the property of being incombustible. It is difficult, however, to find fibres of sufficient length and firmness, to produce objects of any great use. It is sometimes mixed with clay in pottery, to increase its strength. It has also been used for the packing of steam-engines which are of high pressure, or in which steam is used at an elevated temperature.

CEMENTS.----Limestone.--The substances made use of for the uniting medium between bricks or stones in building, are denominated cements. The calcareous cements, composed of a mixture of lime, sand, and water, in consequence of the facility with which they pass from a soft state to a stony hardness, have in common use superseded all others. Lime, in the state of quicklime, is obtained by burning in kilns, any of those natural bodies, in which it exists in combination with carbonic acid; such as limestone, marbles, chalk, and shells. The effects of the burning, or calcination, is to drive off the carbonic acid. If quicklime, thus obtained, be wet with water, it instantly swells and cracks, becomes exceedingly hot, and at length falls into a white, soft, impalpable powder. This process is denominated the slaking of the lime. The compound formed is called a hydrate of lime, and consists of about three parts of lime to one of water. When intended for mortar, it should immediately be incorporated with sand, and used without delay, before it imbibes carbonic acid anew from the atmosphere. Lime, thus mixed with sand, becomes harder, and more cohesive and durable, than if it were used alone. It is found that the sand used in common mortar, undergoes little or no change; while the lime, seemingly by crystallization, adheres to its particles, and unites them together.[A] Cements, composed in this manner, continue to increase in strength and solidity for an indefinite period, the hydrate of lime being gradually converted into a carbonate. The sand most proper to form mortar, is that which is wholly silicious, and which is sharp, that is, not having its particles rounded by attrition.

Fresh sand is to be preferred to that taken from the vicinity of the seashore, the salt of which is liable to deliquesce and weaken the strength of the mortar. The proportions of the lime and sand to each other, are varied in different places; the amount of sand, however, always exceeds that of the lime. The more sand can be incorporated with the lime, the better, provided the necessary degree of plasticity is preserved; for the cement becomes stronger, and it also sets, or consolidates, more quickly, when the lime and water are less in quantity and more subdivided. From two to four parts of sand are used to one of lime, according to the quality of the lime and the labor bestowed on it. The more pure is the lime and the more thoroughly it is beaten or worked over, the more sand it will take up, and the more firm and durable does it become.

Puzzolana.--Water cements, or hydraulic cements, often called, also, Roman cements, are those which have the property of hardening under water, and of consolidating almost immediately on being mixed. Common mortar, although it stands the effect of water very well when perfectly dry, yet occupies a considerable time in becoming so, and dissolves or crumbles away, if laid under water, before it has had time to harden. It is found that certain rocks which possess an argillaceous as well as silicious character, if mixed with lime or mortar, communicate to them the property of hardening in a very few minutes after the mixture has taken place, as well under water as out of it. Substances of this sort have therefore been made the basis of water cements. The ancient Romans, who practised building in the water, and particularly in the sea, to a great extent, first availed themselves of a material of this kind. The Bay of Baiæ, from the coolness and salubrity of its situation, was a place of fashionable resort for the wealthy of Rome, during the summer months. They erected their villas, not only on the seashore, but on artificial quays and islands constructed in the water. To enable them to erect these marine structures, they fortunately discovered, at the town of Puteoli, a peculiar earth, to which they gave the name of pulvis puteolanus, and which is the same now known by the name of Puzzolana. This earth is a light, porous, friable mineral, various in color, and evidently of volcanic origin. When reduced to uniform powder, by beating and sifting, and thoroughly mixed with lime, either with or without sand, it forms a mass of great tenacity, which in a short time concretes to a stony hardness, not only in the air, but likewise when wholly immersed in water.

[A] See Brard and Vicat on this subject.

Tarras.--A substance denominated tarras, terras, or trass, found near Andernach in the vicinity of the Rhine, has been discovered to possess the same property with puzzolana, of forming a durable water cement, when combined with lime. It is said to be a kind of decomposed basalt, but resembles puzzolana. It is the material which has been principally employed by the Dutch, whose aquatic structures probably exceed those of any other nation in Europe. Tarras mortar, though very durable in water, is inferior to the more common kinds, when exposed to the open air.

Other Cements.--It has been found that various other substances, such as baked clay reduced to powder, or the common greenstone calcined and pulverized, afford the basis of very tolerable water cements, with lime. Some of the ores of manganese are also useful for the same purpose.

There are some limestones which have the property of forming water cements when calcined and mixed with simple sand and water. This is usually in consequence of these stones containing a certain portion of argillaceous earth, united with the lime. A water cement found in New York, was used in constructing the locks of the great canal in that State. Another hydraulic cement, containing lime, silex, and alumine, has been found and applied to use in the Union Canal of Pennsylvania. Other parts of the United States have been found to afford very good hydraulic cements.[A]

The cause by which these compounds become hard under water, is not satisfactorily known. It has been supposed, however, and not without reason, that the great attraction for moisture existing in certain argillaceous earths, causes them to absorb immediately the superabundant moisture from the lime, and thus to expedite its solidification. This explanation is rendered more probable, by the fact, that burnt clays, which form good hydraulic cements, cease to do so, if the burning is carried so far as to vitrify them.[B]

Maltha.--The name of maltha, or mastich, is given to those cements into which animal and vegetable substances enter, such as oil, milk, mucilage, &c. Some of these mixtures have afforded, both to the ancients and moderns, cements of great hardness and permanency, but they are not much used.

METALS.----Iron.--Of all the metals, iron is the most useful, and one of the most abundantly diffused. Besides its common occurrence in earths and rocks, it is held in solution by mineral waters, it enters largely into the composition of meteoric stones, and it circulates in the blood of animals, and the sap of vegetables. The amount of iron manufactured in Great Britain in 1836, was estimated at a million of tons. Pure iron is of a bluish white color, of great hardness, malleable, ductile, and tenacious. For its fusion, it requires an intensely high temperature, equal to one hundred and fifty-eight degrees of Wedgewood's pyrometer. When combined with carbon, it forms steel, and is increased in hardness. At a red heat, it becomes soft and more malleable; and at a white heat, may be joined by welding. It is strongly attracted by the magnet, acquires itself the magnetic power, and when in the form of steel, retains it permanently. Cast iron is brittle, and fusible without difficulty, owing to the carbon which it contains. Wrought iron is flexible, and has the properties of the pure metal. In the arts, iron is applied to innumerable uses where strength and hardness are required. It is, however, deficient in durability, being readily corroded with rust, when exposed to the weather, unless protected with a coating of paint. Metallic iron is wrought, while hot, by hammering, rolling, stamping, chiselling, punching, &c.; and when cold, by the same means, also by filing, turning, drilling, cutting, and drawing. Cast iron is commonly melted, when its form is to be changed; but it is finished with common tools when cold, and may be cut with a saw when red hot. Cast iron is now the most common material used in the fabrication of machines, and in Europe it is applied to the construction of bridges, and of roofs. Ships and steam-boats of large size are now made of iron.

To the chemical compounds of iron, we are indebted for copperas, writing ink, prussian blue, &c.

Copper.--Copper is a metal of a light red color, ductile, and malleable, emitting a disagreeable odor when rubbed. It melts at twenty-seven degrees of Wedgewood. When exposed to the atmosphere, it loses its lustre, and becomes covered with a green coating, which is carbonate of copper. This coating preserves the remainder from decay, and is the source of some of its most important uses. Copper is employed to cover the bottoms of ships, and tops of houses; to form various culinary and manufacturers' vessels, also for pumps and water pipes, for engravers' plates, and for coining. When combined with acids, or oxygen, it becomes more or less poisonous, on which account, culinary vessels are coated on the inside with tin. It is this poisonous property, in part, which prevents marine animals from attaching themselves to the bottoms of coppered ships. Copper forms many valuable alloys, among which are brass, which consists of copper and zinc, and bronze, which is made of copper and tin. Its chemical compounds furnish verdigris, blue vitriol, &c. It is wrought by the same modes as iron, but is more easily malleable than that metal when cold.

Lead.--Lead has a light bluish color, with a bright lustre, which becomes quickly tarnished on exposure to the air. It is soft, heavy, very malleable, and melts at six hundred degrees of Fahrenheit's thermometer. By exposure to the heat of a furnace, it is converted into a red oxide. Lead is used for the covering of roofs, for aqueducts, for lining cisterns and tight cavities, for weights, bullets, and shot. Some of its alloys are very valuable, such as pewter, type metal, &c. Its oxides and salts afford paints of different colors, and of great use. Lead is deleterious in its influence on health, and requires great caution in those who work it, or use it, in any other than the metallic state. Injury is most frequently received, by inhaling the dust which rises in the manufactories of red and white lead. In leaden aqueducts a carbonate of lead occasionally forms; but this is insoluble in water, and subsides by its weight.

Tin.--Tin is a white metal, somewhat harder than lead, and producing a peculiar crackling sound when it is bent. It is very malleable, and is beaten for tinfoil into leaves 1/1000 part on an inch in thickness. Its ductility and tenacity are not great. Tin is very fusible, melting at about four hundred and forty-two degrees of Fahrenheit's thermometer. Exposed to the atmosphere, its surface becomes slightly tarnished, but undergoes no further change. On this account, it is largely employed for coating other metals, which are more liable to oxidation. Copper vessels are lined with it, as already stated. Tin plates are sheets of iron coated with tin. Tinfoil with mercury forms the silvering of looking-glasses. Block tin is used to form vessels not intended for exposure to heat. Some of the salts of tin are very valuable in dyeing. The putty used for polishing glass, stones, and metals, is an oxide of lead and tin.

Mercury.--Mercury, or quicksilver, is fluid at common temperatures, and on this account is used in many philosophical and chemical instruments. Attempts have been made to introduce it in certain forms of the steam-engine; but it is objectionable for this purpose, from its tendency to combine with oxygen, and from the unhealthiness of its use to persons occupied about it. Mercury is employed in silvering mirrors, and large quantities are consumed in extracting silver and gold from their ores. Its alloys with other metals are called amalgams. It amalgamates readily with gold, silver, tin, lead, and zinc; difficultly with copper and antimony, and scarcely at all with iron and platina.

Gold.--The value derived from its scarcity, prevents the extensive use of gold in the arts. The power with which it resists tarnishing, and all changes from exposure to air and moisture, renders it desirable for many purposes, and has given rise to the art of gilding. The gold leaf used in gilding is often not more than 1/282000 part of an inch thick, owing to the extreme malleability of the metal. Gold is used in coining, in jewelry, and in coloring porcelain.

Silver.--Silver possesses the same valuable properties as gold, but is more liable to tarnish, especially when exposed to sulphurous vapors, which convert its surface into a sulphuret. Silver is very ductile, but less so than gold, and the leaves into which it is hammered, are usually three times thicker than those of gold. Its uses are well known.

Platinum.--Platinum is the heaviest substance at present known, its weight being twenty-one times and a half that of water. Like gold, it resists tarnishing from oxidation by the air, and it is furthermore capable of resisting an extremely high temperature without melting. It is very malleable, approaches to iron in hardness, and, like that metal, may be welded when hot. It is used for small crucibles and philosophical instruments; also for retorts employed in the manufacture of sulphuric acid.

Palladium.--This is a rare metal, found in minute quantities in the ores of platina and gold. Its color is between those of steel and silver. Its specific gravity is about 12. It is extremely hard, is malleable and ductile, and does not tarnish in the air. It melts at about one hundred and fifty degrees of Wedgewood. It receives a high polish, and has been used in the small way for reflectors, and for instruments requiring hardness and permanency.

Zinc.--Zinc or spelter is a bluish white metal, imperfectly malleable and ductile, but rendered more so by a heat somewhat above that of boiling water. It melts below a red heat, at seven hundred degrees of Fahrenheit. When ignited, it burns with a white flame, throwing off an oxide called flowers of zinc. Zinc is used as a constituent in brass, and in some other alloys. It is an important material in galvanic combinations. It is easily oxidated, and therefore unfit for purposes which require durability.

Nickel.--This metal possesses a white color, and lustre resembling that of silver. It is hard, but malleable, both hot and cold, and can be drawn into wire 1/50 of an inch in diameter. It is difficult to melt, and is not oxidized by air. It becomes magnetic in a degree somewhat inferior to iron, and mariner's compasses have been made of it. It is an ingredient in the compound called German silver.

Antimony.--Antimony is a brittle, whitish metal, of a plated or scaly texture. It is tarnished, but not otherwise altered, by exposure to the air. In type founderies, it is much used to give hardness to lead, in the alloy called type metal.

Cobalt.--Cobalt is a brittle metal, of a reddish gray color, and weak metallic lustre. It is somewhat magnetic, and not easily melted nor oxidized in the air. It is used in coloring glass, &c.

Bismuth.--Bismuth is a metal of a reddish white color, and brittle consistence, not readily oxidated by the air. It is very fusible, requiring little more heat than tin to melt it. It enters into various alloys, one of which is the fusible metal, composed of eight parts of bismuth, five of tin, and three of lead, which melts at a heat less than that of boiling water.

Arsenic.--Arsenic, in its metallic state, is of a bluish white color, easily tarnishing, brittle, and volatile at a low heat. In the state of acid, called white arsenic, it is well known as a violent poison. Arsenic is used in the manufactures of glass and of shot, and furnishes the basis of several brilliant pigments.

Manganese.--Manganese is a metal of a dull whitish color, brittle, extremely difficult to melt, and speedily turning to a dark oxide in the air. The native black oxide of this metal is of great use to chemists in furnishing oxygen. In the arts, it is employed in bleaching, pottery, and glass-making.

COMBUSTIBLE SUBSTANCES, &c.----Bitumen.--This is an inflammable mineral substance, resembling tar or pitch in its properties and uses. Among different bituminous substances, the names naphtha and petroleum have been given to those which are fluid; maltha, to that which has the consistence of pitch, and asphaltum, to that which is solid.

Amber.--Amber is a yellowish, translucent, inflammable mineral, hard enough to receive a fine polish, capable of being wrought into various ornamental articles, and forming an ingredient in some varnishes and lackers.

Coal.--This well-known combustible is composed essentially of carbon, with a proportion, greater or less, of bitumen, a little sulphur, and a remainder of earthy and incombustible matter. True coal burns with a white flame, a black smoke, and bituminous odor. Some kinds, as the Cannel coal, burn readily, with a large flame, and without softening or concreting. Others, as the Newcastle, Liverpool, and Orrel, concrete, or cake, during combustion, and last longer. The poorer coals have usually a large admixture of foreign and incombustible substances. Coal is of great value as a fuel, both in the arts, and for domestic purposes. As it contains more combustible matter, in a given volume, than wood, it is capable of evolving and sustaining more heat than that fuel, within the same furnace, or other cavity. When coal is exposed to heat, but prevented from burnings by the exclusion of the air, it loses its moisture and bituminous portion, and is converted into coke, a fuel bearing the same relation to coal, as charcoal to wood. Coal has of late years been usefully applied to the production of inflammable gas, for the purposes of illumination.

Anthracite.--This combustible, of which the Lehigh, Schuylkill, and Rhode Island coal, are specimens, is harder, heavier, and less black, than the true, or bituminous coals. It burns slowly, without smoke, and with a faint flame. It is more difficult to kindle than most fuels, owing to its greater conducting power, and the high temperature necessary for its combustion; but when once on fire, it produces an intense and lasting heat. It is more durable than the bituminous coals, but requires to be burnt in masses large enough to sustain a high temperature. Anthracite has now become a common fuel in many parts of the United States, and is highly valuable, both for domestic and manufacturing purposes. It is burnt in various furnaces, forges, stoves, and grates constructed for the purpose. In iron works, it is found to occasion less oxidation and scaling of the metal, than any other fuel. But in reverberating furnaces, where a blaze is required, it does not answer the requisite purpose. Most of the anthracites afford inflammable gas, not, however, suitable for purposes of illumination.

Graphite.--This mineral, otherwise called plumbago and black lead, is composed of carbon, with a portion of iron. It is unctuous to the touch, and soils the fingers. It is used for pencils and crayons, and, mixed with clay, is formed into crucibles. Black-lead pencils are made, by inserting the straight edge of a plate of graphite, into a groove made in the wood, and sawing it off, leaving a slender rod of the lead enclosed, which is afterwards covered with wood.

Peat.--Peat is a substance of vegetable origin, dug from bogs and marshes, and capable of reproducing itself in places from which it has been removed. Peat, when dry, is combustible, and is used as such, where better fuel cannot be obtained.

Sulphur.--Sulphur is a simple inflammable body, melting at two hundred and twenty degrees, and taking fire at five hundred, of Fahrenheit. When kept melted for some time, at about three hundred degrees, Fahrenheit, it becomes thick and viscid, and if poured into a basin of water, it becomes ductile, like wax. In this state, it is used for taking impressions of seals. It is also used to form moulds for plaster casts. Sulphur is an ingredient in gunpowder, and enters into many chemical compounds, which are of great use in the arts. Sulphur is burnt to produce sulphuric acid.

MATERIALS FROM THE VEGETABLE KINGDOM.

Wood.--The woody portion of the trunks of trees, is made up of minute tubes or vessels, running longitudinally, having their sides strengthened with rigid fibres, and their interstices filled with cellular substance. In the common trees of temperate climates, these vessels are arranged in concentric layers or cylinders; one layer being added for each year of the tree's growth. The outer layers, being those which transmit the sap, are more porous, soft, and perishable, and are known by the name of alburnum or sap wood. The inner layers are commonly darker colored, more solid, compact, and durable; and are known by the name of heart wood. The heart wood is preferred for most purposes in the arts, its vessels having become in part obliterated by age, and its density and strength increased. Boards are least liable to warp when they are cut through the centre or pith of the trunk. All wood shrinks in drying, and decays when exposed to the weather; but different trees vary greatly from each other, in this respect.

Bark.--Bark is the external investment of the trunks and branches of trees, and consists, when young, of three coats or layers, called the cuticle, the cellular integument, and the liber or inner bark. But during every season, a new liber grows on the inside of the former ones, and pushes them outward, so that old bark is found to consist of numerous cortical layers, each of which was originally a liber. The outermost of these layers gradually become dead and dry, and merely augment the thickness of the bark, without adding to its usefulness in the arts.

Oak.--Numerous species of the oak tree are found in the United States. They are generally distinguished for great strength, but are coarse grained, and prone to warp and crack under changes from moisture to dryness. The live oak of the Southern States (Quercus virens) is prized in ship-building, beyond any native timber. The white oak (Quercus alba) is employed for the keels, side timbers, and planks of vessels, also for frames of houses, mills, and machinery requiring strength; for wagons, parts of carriages, ploughs, and other agricultural instruments. Large quantities are consumed for the staves and hoops of casks, for which they furnish one of the best materials. The bark of the black oak (Quercus tinctoria) furnishes the quercitron used by dyers. Most of the species of oak are employed in tanning, and they all furnish a valuable fuel.

Hickory or Walnut.--The wood of the different species of native walnut or hickory (Juglans, or Carya) is eminently distinguished for weight, tenacity, and strength. It has, however, important defects. It warps and shrinks greatly, decays rapidly when exposed to the weather, and is very liable to the attacks of worms. On these accounts, it is never used for house or ship building, but is chiefly employed for minor purposes, where strength is the chief requisite; as in the teeth of mill wheels, screws of presses, handspikes, capstan bars, bows, hoops, and handles of tools. As fuel, the hickory stands at the head of native trees, and commands a higher price than any other wood.

Ash.--The white ash (Fraxinus Americana) and some other species, are of great utility in the arts. Ash wood is strong, elastic, tough, and light, and splits with a straight grain. It is also durable, and permanent in its dimensions. It furnishes the common timber used in light carriages, for the shafts, frames, springs, and part of the wheels. Flat hoops, boxes, and the handles of many instruments are made of it. It is almost the only material of oars, blocks of pulleys, cleats, and similar naval implements, in places where it can be obtained.

Elm.--The common American elm (Ulmus Americana) is valued for the toughness of its wood, which does not readily split. On this account, it is chiefly used for the naves, among us commonly called hubs, of carriage wheels.

Locust.--The common locust (Robinia pseudacacia) is one of the hardest, strongest, and most valuable of native trees. The larger pieces of its timber are used in ship-building, and the smaller pieces are in great request to form the treenails[A] or pins which confine the planks to the timbers. This tree is liable, in the Northern States, to be perforated by an insect, so that it is often difficult to procure sound pieces of any considerable size. Locust wood is exceedingly durable, when exposed to the weather; and forms excellent fuel.

Wild Cherry-tree.--The wood of this tree (Prunus Virginiana) is of a deep color, hard, durable, and, when properly seasoned, very permanent in its shape and dimensions. In the manufacture of cabinet work, it is much used as a cheaper substitute for mahogany. On the Western rivers, it is sometimes used in ship-building.

Chestnut.--The American chestnut (Castanea vesca, B.) is a large tree of a rapid growth. Its wood is coarse and porous, very liable to warp, and seldom introduced into building or furniture. It is chiefly used for fencing stuff, to which use it is fitted by its durability in the atmosphere. Chestnut is an unsafe fuel, in consequence of its tendency to snap, and throw its coals to a distance.

[A] Commonly pronounced trunnels.

Beech.--The wood of the red beech (Fagus ferruginea) is liable to decay when exposed to alternate moisture and dryness. It does not, however, readily warp, and being smooth grained, it is used for some minor purposes, such as the making of planes, lasts, and card backs. It forms a very good fuel.

Basswood.--The American linden or basswood tree (Tilia Americana) produces a fine-grained wood, which is very white, soft, light, and flexible. It is sometimes employed for furniture, but its chief use is to form the panels of coach and chaise bodies, for which its flexibility makes it well suited.

Tulip Tree.--(Liriodendron tulipifera.) The boards of this tree are sold under the name of white wood, and erroneously under that of poplar. Its wood is smooth, fine grained, easily wrought, and not apt to split. It is used for carving and ornamental work, and for some kinds of furniture. In the Western States, where pine is more scarce, the joinery, or inside work, of houses, is commonly executed with this material, and sometimes the outer covering. In common with basswood, it forms an excellent material for coach and chaise panels.

Maple.--The rock maple, (Acer saccharinum,) and several other species, afford wood which is smooth, compact, and hard. It is much used for cabinet furniture, and is a common material for gunstocks. The wood in some of the old trunks, is full of minute irregularities, like knots. These, if cut in one direction, exhibit a spotted surface, to which the name of bird's eye maple is given; while if cut in another direction, they produce a wavy or shaded surface, called curled maple. This last effect, however, is more frequently produced by a mere serpentine direction of the fibres. The distinctness of the grain may be increased by rubbing the surface with diluted sulphuric acid. Maple wood forms a good fuel. It is not very lasting, when exposed to the weather. The sap of the rock maple, and of one or two other species, yields sugar on being boiled.

Birch.--The white or paper birch (Betula papyracea) has properties similar to those of the maple, and is appropriated to the same uses. Its cuticle or outer bark, is made by the Indians into canoes. The lesser white birch (B. populifolia) is a perishable tree, of little value. The black birch, (B. lenta,) known for its aromatic bark, affords a firm, compact, dark-colored wood, much valued for furniture, and sometimes used for screws and implements requiring strength. The yellow birch (B. lutea) is applied to the same uses as the last, and makes good fuel.

Buttonwood.--The buttonwood or plane tree (Pla-tanus occidentalis) is in some of the Northern States improperly called sycamore. It is one of the largest inhabitants of the forest, and Michaux states that trees are found in the Western States which measure forty feet in circumference. This majestic tree is chiefly valuable for its shade, as the wood is perishable, and prone to warp.

Persimmon.--(Diospyros Virginiana.) The heart wood is dark colored, compact, hard, and elastic; and is used in the Southern States for screws, shafts of chaises, and various implements.

Black Walnut.--(Juglans nigra.) This tree is rarely found north of New York. Its heart wood is of a violet color, which, after exposure to the air, assumes a darker shade, and finally becomes nearly black. This wood, when deprived of its white part, or sap, remains sound for a long time, even if exposed to air and moisture, and is not attacked by worms. It is very strong and tenacious, and when seasoned is not liable to warp or split. It is used in the Middle and Western States for furniture, for gunstocks, for naves of wheels, and, to a certain extent, in house and ship building.

Tupelo.--Different species of the genus Nyssa have received, in the United States, a great variety of common names, among which tupelo, pepperidge, and gum tree are the most common. In Massachusetts, the name hornbeam is improperly applied to one of them. Their wood is smooth grained, and remarkable for the decussation or interweaving of the fibres, which renders it almost impossible to split the logs. This quality causes several of the species to be in demand for naves of wheels, hatter's blocks, and implements requiring lateral tenacity.

Pine.--The American pines exceed all other native trees for the value and variety of their uses. The white pine (Pinus strobus) has a very tall, straight trunk, the wood of which is light, soft, homogeneous, and easy to work. It is remarkably exempt from the common fault of timber, that of decaying in the open air, and of changing its dimensions with changes of weather. On these accounts, it is extensively employed for most of the common purposes of timber. In the Northern States, masts of vessels are commonly made of it. Frames of houses and of bridges are also formed of it; its defect of strength being more than balanced by its steadiness and durability. Its boards form almost the only material used in the Northern States for the joiner's work, or inside finishing of houses; and for this use it is exported to other countries. Ornamental carving is commonly executed in this material. The southern pitch pine (Pinus palustris; L.) covers extensive barrens in the Southern States, and yields vast quantities of tar and turpentine. Its wood is appropriated to the same objects as that of the white pine, but is harder and stronger, and therefore preferred for planks, spars, floors, decks, &c. Many other species of pine exist on this continent, partaking qualities like those already described, but most of them harder than the white pine.

Spruce.--The black and white spruce belong to the race of trees commonly called Firs. They are both valuable, but the black spruce (Pinus nigra) unites in a peculiar degree the qualities of strength, elasticity, and lightness, together with the power of resisting exposure to the weather. It is much sought after for the smaller spars of vessels, such as the booms, yards, and topmasts.

Hemlock.--The hemlock tree (Pinus Canadensis) is inferior to the other firs in quality, though it grows to a large size. It is coarse grained, often twisted, and cracks and shivers with age. It furnishes an inferior sort of boards, used in covering houses. Its bark is valuable in tanning.

White Cedar.--This tree (Cupressus thuyoides) occupies large tracts denominated cedar swamps. The wood is soft, smooth, of an aromatic smell, and internally of a red color. It is permanent in shape, and very durable; and esteemed as a material for fences. Large quantities of shingles are made of it. It is a favorite material for wooden wares, or the nicer kinds of cooper's work.

Cypress.--The cypress tree of the Southern States (Cupressus disticha) is light, soft, and fine grained; and at the same time elastic, with a considerable share of strength. It sustains heat and moisture for a long time, without injury. In the Southern States, and on the Mississippi, it is much employed for fences, and for the frames, shingles, and inside work of houses.

Larch.--The American Larch (Pinus microcarpa) is called hackmatack and tamarack, in different parts of the Union. Its wood is strong, elastic, and durable; and is highly prized, in places where a sufficient quantity can be obtained, for naval and civil architecture.

Arbor Vita.--This tree (Thuya occidentalis) is of the middle size, and frequently called white cedar. The wood is reddish, fine grained, very soft, and light. It bears exposure to the weather, with very little change, and is esteemed for the posts and rails of fences.

Red Cedar.--(Juniperus Virginiana.) The name of savin is in some places improperly applied to this tree. Unlike the white cedar, it grows in the driest and most barren soils. The trunk is straight, and knotted by small branches. The heart wood is of a bright red color, smooth, and moderately soft. It exceeds most other native trees in durability, and is in particular request for posts of buildings, though it is difficult to obtain it of large size.

Willow.--The most common kinds of Salix or willow, about our sea-ports, are European species which have become naturalized. Their wood is soft, light, and spongy. Willow charcoal is used in the manufacture of gunpowder. The osier and some other species, with long slender shoots, are extensively cultivated to form wicker work, such as baskets, hampers, and the external coverings of heavy glass vessels.

Mahogany.--In the manufacture of cabinet furniture, mahogany (Swietenia mahagoni) has taken precedence of all other kinds of wood. Its value depends not so much on its color, as on its hardness, and the invaluable property of remaining constant in its dimensions, without warping or cracking, for an indefinite length of time. The same qualities which render it suitable for furniture, have given rise to its employment for the frames of philosophical instruments, and of delicate machinery. Mahogany is imported from the West Indies, and different parts of Spanish America.

Teak Wood.--(Tectona grandis.) The teak tree is a lofty inhabitant of the forests of India, and affords a kind of timber of the highest value in ship-building. This wood is exceedingly hard, firm, and durable, and many vessels are built of it in the British Eastern dominions.

Lance Wood.--(Guatteria virgata.) This is a tree of middle size, growing in the West Indies, whence it is imported chiefly to form the shafts of carriages. It is peculiarly tough, strong and elastic, and surpasses any of our native woods in this respect. Its grain is more close than that of ash, and is therefore more suitable for carving and for receiving varnish.

Boxwood.--The box tree (Buxus sempervirens) is imported from the south of Europe. Its wood is of a well-known yellowish color, hard, compact, smooth, tough, and not liable to crack. Musical wind-instruments are commonly made of it; also mathematical measuring instruments. The handles of many tools, and various articles of turners' work, consist also of this material. Wood engravings are cut upon the end of the grain of boxwood.

Lignum Vitae.--The wood of the Guiacum officinale is employed in the arts under this name. It is dark colored at the heart, strong, exceedingly hard, and so heavy as to sink in water. It is impregnated with resin, and on this account durable in liquids. Handles of tools, boxes of gudgeons, wheels of pulleys, castors, balls, stop-cocks, mallets, &c, are made of it. It is imported from the West Indies and South America.

Several other tropical woods are imported for use by cabinet-makers, such as rose wood, ebony, satin wood, &c. They are generally hard, colored woods, susceptible of a fine polish. Satin wood (Swietenia chloroxylon) is thought poisonous to the hands of the workmen.

Cork.--Cork is a fungous substance growing on the bark of a species of oak (Quercus suber) in the south of Europe. Its lightness and elasticity give it an aptitude for certain purposes, in which it would be difficult to find a substitute.

Hemp.--Hemp is the fibrous portion of the bark of an annual plant, (Canabis sativa,) and is of great use in the manufacture of cordage and canvass. The fibres are separated from the rest of the stalks, by the decomposition of the latter. In the process of dew rotting, the hemp is exposed on the grass for a number of weeks to the weather. In that of water rotting, it is immersed for a part of the time in water, and subsequently exposed to the weather. By these processes, the solid parts of the hemp decay; while the flexible fibres remain strong and but little impaired. The decayed portion is afterwards broken up, by the operations of an instrument called a brake; and sometimes by a mill or stone roller. The chaff is separated, from the fibres by the strokes of a wooden scotching or swingling knife; and the fibres still further cleansed by combing them on an instrument called a heckle.

Flax.--Flax is also the fibrous bark of an annual plant, (Linum usitatissimum,) which is smaller and finer than hemp; and constitutes the material of linen cloth. Flax is rotted, and subsequently dressed, much in the same manner as hemp. When, however, it is intended for finer uses, as for cambric, lace, &c, it is scraped with a blunt knife upon leather, and the fibres separated and straightened with a brush. A method has been introduced in England, of dressing, by machinery, flax, in its recent state, without rotting. This method is represented as highly economical, affording more flax, and of a stronger texture, than that produced in the common way[A]. The fibres of flax and hemp are long, straight, and unyielding, so that they cannot well be spun by the same machinery which is used for cotton and wool. When viewed through a microscope, they are found to be cylindrical and jointed, like a cane.

Aloes.--A large family of tropical plants are known by the name of Aloes. The leaves are thick, juicy, and thorny, and afford the drug known by the same name. The leaves of some species contain a fibre, which, when twisted into ropes, is said to be several times stronger than those of hemp prepared in the same way. They contain a resinous substance which renders tarring unnecessary.

Pine-apple.--The pine-apple plant is well known, and valued for its delicious fruit. It has lately been found that its leaves contain an extremely fine, glossy, and silken fibre, easily separable by beating and washing. The ultimate fibres are finer than those of cotton or linen, and are applicable to the same purposes.

Several species of Agave also afford from their leaves very strong, flexible fibres, one of which is known by the name of Sisal hemp.

Manilla Hemp.--The white hemp brought from the East Indies, is said to be obtained from a species of Musa or plantain tree. Its fibres are long, whitish, parallel, and exceedingly strong. They are now extensively manufactured into cordage in this country. Ropes made of it are light, elastic, and strong, but do not admit of being tarred in the manner of common ropes.

New Zealand Flax.--(Phormium tenax.) This plant was employed by the natives of New Zealand for cordage and clothing, at the time of the discovery of that island. It produces one of the strongest vegetable fibres known, having a fine, white, silken appearance. It is readily cultivated in Great Britain and Ireland, and has lately become a subject of attention among manufacturers. This plant, like the Manilla hemp, receives tar with difficulty, when made into cordage; but this defect is said to be overcome by steeping it forty-eight hours in a weak solution of potash or soda.

[A] See Brande's Quarterly Journal, vol. iv. p. 329.

Cotton.--Cotton is the product of the Gossypium herbaceum, an Oriental plant, now cultivated in most parts of the world, which possess a sufficiently warm climate. It grows in pods, forming a light, woolly investment to the seeds; and seems intended by Nature to assist in their dispersion by the winds. The fibres of cotton are extremely fine, delicate, and flexible. When examined by the microscope, they are found flat like a ribbon, with a border like a hem on each side. Their direction is not straight, but contorted; so that the locks can be extended or drawn out without doing violence to the fibres. These properties render cotton peculiarly adapted for the operations of machinery, and have given employment to a vast amount of manufacturing skill and industry, both in Great Britain and this Country.

Cotton, after being gathered, is cleansed from the seeds by a machine called a gin, of which there are two kinds. The roller gin consists essentially of two small cylinders revolving in contact, or nearly so, with each other. The cotton is drawn between these rollers, while the seeds, being too large to pass, are left behind, and fall out on one side. The sme gin, invented by Mr. Whitney, is intended for those sorts of cotton, the seeds of which adhere too strongly to be separated by the former method. It consists of a receiver, having one side covered with strong parallel wires, placed like those of a cage, and about an eighth of an inch apart. Between these wires enter an equal number of circular saws, revolving on a common axis. The teeth of these saws entangle the cotton and draw it out through the grating of wires, while the seeds are prevented by their size from passing. The cotton thus extricated is swept off from the teeth of the saws by a revolving cylindrical brush; and the seeds fall out at the bottom of the receiver.

Straw.--The wheat straw, used in Tuscany, in the manufacture of Leghorn hats, is gathered before the ear is ripe, the wheat having been sown very close, so that it is produced of an inferior or dwindled size. It is bleached by exposure to the dew, sun, and air, and afterwards by fumigation with sulphur. It may also be bleached by chloride of lime. The straw, thus produced, is woven into braids, which are afterwards joined at their edges, to form hats. In this country, hats of great delicacy have been made from various species of grass.

Palm Leaves.--The leaves of the large fan-leaved palm are plaited, fibrous, and firm. In tropical climates, they are much used for fans. Of late years, these leaves have been imported into the Northern States, in great quantities, as a material for the manufacture of hats. They are split by machinery into narrow, even strips, which are afterwards braided in the manner of straw.

Turpentine.--Turpentine is the juice which exudes from pine trees. The Southern pitch pine furnishes most of that used in commerce. It is procured by making incisions, or cavities, in the trunk, and dipping out the turpentine which collects. Tar is an impure turpentine, obtained by burning. The resinous parts of the wood, called lightwood, are collected in pits, and being set on fire at the top, a part of the turpentine is burnt, while the rest is melted and flows out at the bottom. Pitch is tar inspissated by boiling or burning. If turpentine be distilled, the volatile portion, which passes over, is the oil or spirit of turpentine, while the solid part left behind is rosin.

Caoutchouc.--This substance, called also elastic gum, and India rubber, is obtained from different vegetables, but chiefly from the Jatropha elastica. It exists in the form of juice, and is dried by applying it, in successive coatings, to clay moulds of various shapes. After it is dry, the clay is crushed and shaken out. This substance is wonderfully flexible and elastic, and restores itself instantly, after being extended to many times its original dimensions. It is inflammable, and used by the inhabitants of Cayenne for lights. It is insoluble in water, and in alcohol; but dissolves in ether, and in oils. These solutions have been used for varnishes, but have the disadvantage that they do not readily dry. Water of ammonia dissolves caoutchouc slowly, requiring to be digested with it for some months. A mixture of oil of turpentine and alcohol,[A] is a solvent which has the property of drying more readily and restoring the elastic properties of the gum. The purified naphtha from coal tar has the same property.[B] If caoutchouc be distilled at six hundred degrees of Fahrenheit, a liquid is obtained which dissolves caoutchouc, and also copal and other resins. It is the lightest of known liquids, and its vapor is heavier than any gas.[C] Slips of India rubber may be made to cohere by boiling them in contact for a certain time in water, and in this way some articles are made. When heated to about two hundred degrees of Fahrenheit, this substance may be spread by rollers upon cloth, so as to form a permanent coating. Caoutchouc is of great use in the formation of many instruments, which require to be elastic, and impenetrable to water. Shoes are now made of it in great numbers, and are found to exclude perfectly the wet. The solution of this gum, spread upon leather and cloth, renders them water-proof, and even air-tight. The manufacture of India rubber cloths has given rise to a new branch of industry within a few years past. An elegant elastic web is made from fibres of caoutchouc wound with silk and woven. The elasticity which is lost by stretching, is restored by a hot smoothing-iron. Its adhesiveness and friction are the properties by which India rubber erases black lead from paper.

[A] Chaptal. Chimié appl. aux. Arts.

[B] Turner's Chemistry.

[C] Mr. Faraday states that the liquid caoutchouc, or juice, as it came from the south of Mexico, was a pale, yellow, thick, creamy-looking substance, of a uniform consistency, with a disagreeable acescent odor. When exposed to the air in films, it is soon dried, leaving caoutchouc of the usual appearance and color. One hundred parts of the sap left nearly forty-five of solid matter. Heat caused an immediate coagulation of the sap, the caoutchouc separating in a solid form. When the sap is purified by repeated washings with water, the caoutchouc rises each time to the surface; it is obtained of a white color, and afterwards, when perfectly dry, it becomes transparent, colorless, and elastic. A solution of caoutchouc in oil was obtained by mixing the juice with olive oil, and heating the mixture so as to drive off the aqueous parts. This promises to be a useful element in varnishes. See Brande's Journal, No. xli. page 19.

Oils.--Oil is an inflammable liquid, which does not unite with water. Volatile oils are those which evaporate, or may be distilled without change, by a moderate heat. Of these, the oil of turpentine is an example. They are used in the arts for solvents, and in varnishes. Fixed oils are those which do not evaporate without decomposition, or chemical change. They produce an unctuous stain, which is not discharged by heat. They do not boil at a temperature much short of that of melting lead. They unite with alkalies, forming soaps. Some of them are called fat oils, which do not lose the unctuous character on exposure to the atmosphere, but assume a state like that of tallow; such, for example, as olive oil. Others are called drying oils, which become solid in the air, after exposure for a certain time, and remain transparent. This is the case with linseed oil. Fat oils are used in the arts, to give flexibility to other materials; to diminish their friction, and to protect them from water. Drying oils are largely consumed as ingredients in paints, printers' ink, and varnishes.

Resins.--Various resinous substances are employed in the arts. They are fusible, inflammable, soluble in oil and alcohol; but insoluble in water. For ordinary purposes the rosin of the pine is employed, being the cheapest. For varnishes, copal, mastic, animé, and some others are used. The basis of sealing wax is the resin called lac, which is deposited on trees in India by an insect.

Starch.--Starch or Fecula, is a white substance, obtained from farinaceous grains and roots. It is insoluble in cold water, but dissolves readily in hot water. In alcohol it does not dissolve. In Europe, starch is commonly made from wheat. In this country it is prepared, for manufacturing purposes, from potatoes. For this object, the potatoes are rasped, or ground up, by a machine, to a pulp. This pulp, when washed with cold water, yields a white powder, which, on subsiding, proves to be pure starch. It is heavier, and goes further, for practical purposes, than the starch of wheat. Starch is largely consumed in cotton factories in the process of dressing, &c.

Gum.--The true gums are those which dissolve in water, either hot or cold, and form with it a thick, mucilaginous solution. They do not dissolve in alcohol, nor melt by heat. The species principally used, are, the gum arabic, gum tragacanth, and gum Senegal. Gum, in the state of mucilage, is employed to give firmness and lustre to linen. Calico printers use it in great quantities, to give their colors such a degree of consistency, as will prevent them from running upon the cloth. It is made to form an ingredient in writing ink, and in water colors, for the same reason.

MATERIALS FROM THE ANIMAL KINGDOM.

Skins.--The cutis, or true skin of animals, from which leather is made, is composed of fibres irregularly situated, and closely interwoven. They are capable of being dissolved by long boiling in water, and are found to consist almost wholly of gelatin, or glue. The skins of a great variety of animals are used in the manufacture of leather. It has been found that those skins which are most flexible, and most easily dissolved, afford the poorest leather and the weakest glue; while those which are tough, and difficult of solution, yield leather and glue of the best quality.

Hair and Fur.--The hairs of animals consist of slender, flexible tubes, having a consistence like that of horn, and possessing the chemical properties of coagulated albumen. The surface of hairs is covered with minute scales or asperities, which give them a rough feel when they are rubbed upwards; and which cause them to entangle each other in the processes of felting and fulling. Fur consists of very fine hair, thickly set, and commonly contorted. It is a very slow conductor of heat, and is provided by Nature for the clothing of animals in high latitudes. Hair is a durable and very elastic substance, and is converted to many useful purposes. By means of a linen warp, it is woven into cloth for furniture. It forms the most elastic stuffing for cushions and mattrasses. It is combined with mortar in plastering, to increase its cohesiveness. Furs are converted to important uses, in clothing and in felting.

Quills and Feathers.--The structure of the quills and feathers of birds is remarkably fitted to combine strength and elasticity with lightness; the mechanism of the tube, shaft, and feathering, being all adapted to this purpose. The tube or barrel of a quill, consists of two laminæ or layers, the outermost of which has transverse fibres, and the inner, longitudinal. It is the first of these, which is scraped off to prepare the quill for splitting. Quills are rendered transparent by exposing them to heat and moisture. The process recommended by M. Schloz, is to expose the quills to hot steam, by suspending them in a covered vessel, which contains water in the bottom, and is kept boiling for four hours, the quills being immersed in the vapor only. At the end of this time, they are withdrawn, and the next day cut, wiped, and dried with a moderate heat. Feathers, as they are obtained from common birds, and down, which is procured from the aquatic birds of northern climates, are among the most elastic substances known, and also the slowest conductors of heat. These properties are the foundation of their usefulness. The chemical composition of feathers is nearly similar to that of hair.[A]

Wool.--Wool is a fine, soft, long, and contorted hair, derived chiefly from the sheep. It is said to be the result of cultivation, and not to be found in the wild sheep, which is covered with short hair. Removal to a tropical climate causes the fleeces of sheep to fall off, and to be succeeded by a covering of short hair. Wool is an invaluable material in the clothing of civilized nations. The fineness and position of its fibres enable it to be drawn out like cotton, and to be spun by machinery. Their roughness and tendency to curl, cause the fibres to be consolidated in the process of felting.

[A] Feathers are purified by exposing them to heat; also by immersing them in lime-water for several days, and afterwards washing them with pure water, and drying. This process extracts the animal oil.

Silk.--Silk is spun by the larvae or caterpillars belonging to different species of Phalaena. It forms the ball, or cocoon, in which the silk-worm envelopes itself in passing to the chrysalis state. The fibre, which constitutes this ball, is so small, that a single thread, when unwound, is often twelve hundred yards in length. The original threads are too fine for manufacturing purposes, and therefore, in winding or reeling them off from the cocoons, the ends or threads of several cocoons are joined together, and reeled out of warm water, which softens their natural gummy covering, and causes them to cohere into a single thread. Silk, as it is spun by the animal, is of a color varying from white to reddish yellow. Its texture is very strong and elastic. It communicates to water a mucilaginous character, owing to the solution of its gummy part; but the silk itself is insoluble in water or alcohol.

Bone and Ivory.--The bones of animals are composed of a white, hard, lamellar, substance, consisting chiefly of phosphate of lime, with a small portion of other earths, and impregnated with oily and gelatinous matter. Exposure to heat causes them to soften and crumble. Bone is used in the arts for the handles of cutlery, and various articles of turners' work. It is whitened by exposure to the sun and weather, and sometimes by the use of chlorine gas. It is wrought by sawing, turning, &c., and polished with pumice and tripoli. Ivory is the material of the elephant's tusks. It agrees with bone in its principal properties, but is more compact, hard, and white, and receives a finer polish. When burnt in close vessels and afterwards reduced to powder, it furnishes the pigment called ivory black.

Shell.--The shells of marine animals differ from bone in being composed of carbonate, instead of phosphate of lime. They are therefore burnt, in some places on the seacoast, to afford lime for mortar. The inside of the shell of the pearl oyster affords a beautiful substance called mother of pearl, which is manufactured into toys, counters, handles of cutlery, &c.

Horn.--Horn differs from bone, not only in its texture, which is softer, but also in its composition, being composed chiefly of animal matter, resembling coagulated albumen, and containing but little lime. Horn, when heated, becomes soft, flexible, and plastic, capable of being cemented and pressed by moulds into a great variety of shapes.

Tortoise Shell.--This substance exists in the form of plates on the outside of the shell of a species of sea turtle (Testudo imbricata.) It resembles horn in its general properties, and like that article may be wrought by softening it in boiling water, and subjecting it, while hot, to pressure in moulds. The edges of different pieces, by pressing them with heated irons, may be joined together and made to cohere firmly.

Whalebone.--This substance is obtained from the mouth of several species of whale, where it exists in the form of plates arranged on the outer edge of the upper jaw. These plates terminate in a kind of hair. Whalebone, in its texture and chemical properties, is very similar to horn. It is strong, light, and elastic; on which accounts, it is applied to various mechanical uses. Whalebone, when heated by steam, or boiling water, becomes more flexible, and if bent into any shape, retains its form on cooling. Hence it has been manufactured into various woven fabrics. It may be cemented in the same way as horn or turtle shell.

Glue.--The skins, tendons, membranes, &c., of animals, are composed principally of a substance known in chemistry by the name of gelatin. This substance is not soluble in cold water, but dissolves freely in boiling water, and on cooling assumes the state of gelly. It has great affinity for tannin, which exists in astringent barks; and on this affinity depends the manufacture of leather. Common glue is impure gelatin, obtained from hoofs, ears, and refuse portions of hides. These are first cleansed, then boiled to a gelly, which, on cooling, is cut into squares and dried upon nets. Size is a finer kind of glue, made with more care, from select materials. Isinglass is a still more delicate sort, prepared from the swimming-bladders of fish. Glue is a cementing material of unequalled strength, for wood and fibrous substances. It is employed, in different states of purity, by carpenters, hatters, paper makers, linen manufacturers, gilders, painters in distemper, and refiners of liquors. In the state of a stiff gelly, it forms, with treacle, the elastic rollers, used to distribute and apply the ink, in printing.

Oil.--The oil of animals belongs to the class of fixed and fat oils. The oil of those animals which live in a cold medium, as whales, remains fluid at common temperatures; but that of most land animals becomes solid, when cooled below the heat of the living body. Tallow, the hardest kind, is obtained from ruminating quadrupeds. Animal oils are appropriated to the same purposes as the vegetable; but their great use is to furnish light, by their combustion.

Wax.--Wax, in its crude state, is obtained by melting the honeycomb of the bee. It is commonly classed with vegetable substances; but the experiments of Huber have shown, that it is produced by the bees themselves, and not gathered by them directly from plants, as was formerly supposed. Wax melts with a gentle heat, at one hundred and forty-two degrees of Fahrenheit, is inflammable, dissolves in boiling alcohol, ether, and fixed oils; but is insoluble in water. Beeswax is deprived of its coloring matter by bleaching. To effect this, the melted wax is suffered to run through holes in the bottom of a vessel, upon the surface of a cylinder which is kept revolving in water, by which means the wax is spread out, and cooled in the form of thin laminæ or ribands. It is then exposed to the light and air upon frames, and occasionally wet, till the bleaching is completed. Bayberry, or myrtle wax, is a harder substance than beeswax, obtained from the berries of the Myrica cerifera, by boiling them in water.

Phosphorus.--Phosphorus is a simple combustible body, usually obtained from animal bones. It is of a soft, waxy, consistence, and is luminous in the atmosphere at common temperatures. At one hundred and forty-eight degrees of Fahrenheit, it takes fire and burns with great brilliancy. On this account, it should be kept in water. Phosphorus is the agent, in some kinds of apparatus, for procuring fire.

WORKS OF REFERENCE.--Among the works, which may be usefully consulted on the subjects of this chapter, are CLEVELAND's Mineralogy, 2 vols. 8vo. 1822;--BRARD, Minéralogie appliquée aux Arts, 3 tom. 8vo. Paris, 1821; EVELYN's Sylva, 2 vols. 4to. edit. of 1812; MICHAUX, North American Sylva, 3 vols. 8vo. 1817;--TREDGOLD's Elementary Principles of Carpentry, 4to. 1820;--THOMSON's Chemistry;--URE's Dictionary of Chemistry;--VICAT, Recherches sur les Chaux, &c.; URE's Dictionary of the Arts, 1839.