the steel of a portion of its carbon, which confers the property of imparting a keen edge, so essential to cutting instruments. Articles of iron and steel ought to be annealed in close vessels, or in a trough or recess made of fire brick, and covered up with ashes or clean sand; or if a small vessel be employed, the cover may be of the same material as the vessel. The oven or trough is heated by the flame of a furnace passing under and round it until the whole is at a red heat. It is then allowed to cool without letting in the air. Goods thus treated become softer than by the common method, and the surfaces have a metallic whiteness imparted by the carbonaceous matter of the ashes. Annealed goods lose their brittle character so that they can be bent without breaking. The fracture before being annealed is smooth and short; after that process it is rough, and exhibits bright parts of a crystalline appearance. Copper and brass suffer less from being annealed in an open fire than iron and steel: but a close vessel is necessary in order to preserve their metallic lustre. Very small brass wire is sometimes annealed by holding it in the flame of burning hay and straw.

Soft metals, such as tin, lead, and zinc, after being hardened by hammering may be softened by the action of boiling water. Most of the hard metallic alloys when made red hot, suffer no great change whether they be suddenly quenched in water or not. Pure hammered iron after annealing becomes equally soft whether it be cooled suddenly or slowly; but some inferior kinds of iron become hard by immersion in water. Steel receives by sudden cooling that extreme degree of hardness, combined with tenacity, which adapts it beyond every other material for cutting tools, especially as it admits of being regularly graduated from extreme hardness to the softest state when subsequently heated or tempered. The following are a few examples of the method of treating steel, so as to produce extreme hardness, and ending with the reverse condition. A thin heated blade worked between a cold hammer and anvil, or other good conductors of heat, becomes perfectly hard. A thicker piece of steel cooled by exposure to the air on the anvil becomes rather hard, but not too hard to be filed. When it is placed on cold cinders, or other bad conductor of heat, it becomes softer; but it becomes softer still when placed in hot cinders, or within the fire, and allowed to cool, by gradual extinction. When the steel is encased in close vessels with charcoal powder, and raised to a red heat, and allowed to cool in the furnace, it assumes its softest state; unless, indeed, it be made to undergo partial decomposition by enclosing it in a close vessel with iron turnings or filings, or with the scale from the smith's anvil, or with lime or other matters which attract carbon from its surface; this reduces it to the state of pure soft iron. Some descriptions of cast-iron may be made as hard as the hardest steel, forming what are called chilled iron castings. The reverse process is annealing with partial decomposition; this forms what is called

The change which is produced by annealing is not well understood. Most of the malleable metals assume two distinct forms; one crystalline, which is the result of slow cooling, and the other fibrous, which is brought about by hammering or rolling. If hammered or rolled beyond a certain point, the metals become so hard that they cannot be bent without breaking. If annealed beyond a certain point the metals become crystalline. Thus, zinc may be drawn into a very flexible and tenacious wire, but if kept in boiling water too long it resumes its original brittleness, and displays a crystalline appearance when broken. The particles of the metal change their arrangement without altering the external form, and this change may be brought about in various ways; thus, brass wire loses its tenacity by exposure to the fumes of an acid, and even by air acting on its surface in a damp atmosphere. Hence it is necessary to preserve wire, such as is used in the manufacture of pins, in a dry air or under the surface of water.

ARNOTTO. ANNOTTA, a red colouring matter obtained from a plant (Bixa orellana), Fig. 49,

common in the West Indies, where it is extensively cultivated on the banks of rivers, sometimes giving its name to the district, as Annotta Bay, on the northern coast of Jamaica. The arnotto plant is a small tree with deep-green, shining leaves, and clusters of purplish flowers. These are succeeded by bristly heart-shaped capsules, or seed-pods, containing numerous seeds covered with a soft, sticky rind of a bright red colour. It is a thick extract of this rind made into cakes and balls, which forms the arnotto of commerce. The cakes are usually of two or three pounds weight each, and are packed in casks with

Arnotto dissolves entirely in water or milk, and is much used in colouring cheese and butter in England and Holland, the colouring matter being diffused in the milk previous to the manufacture. The Spaniards employ this substance in colouring and flavouring their chocolate and soups, esteeming it wholesome and stomachic. Dyers obtain from it the reddish colour called aurora. The liquid sold under the name of Nankin dye is a solution of arnotto in potassa, and pure water. A solution is also made in alcohol, and used in varnishing and lacquering. The Indians paint their persons with a mixture of arnotto, gum, and lemon-juice, as a preservative against the attacks of insects. Arnotto also has a fabulous reputation of being an antidote to the poison of the cassava root, which has fatal properties when raw, although, when cooked, it is a wholesome food. The consumption of arnotto in Great Britain has greatly increased of late years. In 1820, it amounted to but little more than 50,000lbs.: three or four times that quantity is now imported. The botanical position of the arnotto plant, is in a small group of tropical plants, called bixads, now included by Lindley in the natural order Flacourtiacea.

ANTHRACITE, [See COAL.]

ANTIMONY is a metal discovered by Basil Valentine, a monk of Erfurth, and an alchemist of the fifteenth century. It is related that having thrown some of it to the hogs it purged them violently, after which they became fat; and thinking that his brother monks might derive benefit from a similar dose, he administered it; but the effects were fatal, for the monks died; hence the medicine was called anti-moine or anti-monk. The ancients appear to have been acquainted with some of the compounds of this metal,' which Pliny names stibium, a word still used to express the metal, or in chemical symbols Sb. Its equivalent is 129.

Metallic antimony has a distinct platy, crystalline structure, and by particular management may be obtained in crystals which are rhombohedral; this metal has a bluish white colour, and a strong lustre ; it is very brittle, and can be easily reduced to powder. Its specific gravity is 6.8. It melts at a temperature just short of redness, and boils and passes off in vapour at a white heat. It has a peculiar taste and smell, especially in the state of vapour. Antimony is not oxidized by the air at common temperatures; but when strongly heated it burns with a white flame, producing an oxide which often forms beautiful

(1) The sulphuret was used by the ladies of Rome as a cosmetic for painting the eyebrows and the edges of the eyelids. The smoke-black of a kind of resin, or of the shells of almonds, is now used for the purpose by females in the East.

Antimony is dissolved by hot hydrochloric acid with evolution of hydrogen, and the production of a chloride formerly called butter of antimony, a substance sometimes used with sulphate of copper for bronzing gun-barrels, the iron decomposing the chloride, and depositing a thin film of antimony on its surface. Nitric acid oxidizes antimony into antimonic acid. Sulphuric acid has scarcely any action on it.

Antimony is found in many parts of Europe, but the mines of this metal are not numerous; it occurs native in Sweden, in France, and in the Hartz; but its principal ore is the sulphuret, which occurs massive and crystallized. There are several varieties, of which the most common is the radiated. This is of a grey colour, brittle, and frequently crystallized in four and six-sided prisms. The sulphuret is associated with quartz, sulphate of baryta, and carbonate of lime, from which it is separated by fusion; a method of purification analogous to the mechanical preparation of other ores, but on account of the great fusibility of the sulphuret of antimony this separation is accomplished by means of heat. For this purpose the ore is placed in large crucibles, C C, (Fig. 50,) perforated with a number of small holes in

of antimony and sodium. The object of the carbonate of soda is to reduce a portion of the sulphuret of antimony by forming sulphuret of sodium, which combines with the remainder of the sulphuret of antimony in such a way as to cause it to collect in the scoria.

Fig. 51.

In the department of La Vendée, in France, this method is improved by heating the ore on the concave sole of a reverberatory furnace. This sole is formed of clay and charcoal, and communicates with a recipient outside by means of a channel, the upper extremity of which is stopped with ashes during the melting. The charge consists of 7 or 8 cwt. of the ore, and each tapping yields about 4 cwt. of crude antimony, which is about 50 per cent: in other places the yield is not more than from 30 to 40 per cent. Wood is the fuel employed.

When sulphuret of antimony is roasted in contact with the air, oxide of antimony is formed, which unites with that portion of the sulphuret which has not been decomposed. In this way several oxysulphurets are formed, which melt, and yield in cooling some brown vitreous substances, which are known in commerce as glass of antimony, liver of antimony, or crocus. Glass of antimony consists of 8 parts of oxide and 1 of sulphuret. It is transparent, and of a reddish yellow colour. Crocus contains 8 parts of oxide and 2 of sulphuret; it is opaque, and of a yellow-red colour. Liver of antimony is opaque, and of a deep brown colour; it consists of about 4 parts sulphuret and 8 parts oxide. The reduction of the crude antimony to the metallic state is attended with some difficulty, for antimony is a metal sufficiently volatile to occasion great loss, but not volatile enough to pass over by distillation. The first process in the reduction is to roast the crude antimony at a very moderate heat, whereby, in 100 parts, 86 parts ought to be converted into protoxide, and the sulphur disengaged, to be converted into sulphurous acid; but in practice not more than about 60 or 65 parts of the protoxide are obtained. These 65 parts are next mixed with 8 or 10 parts of charcoal-powder, sprinkled with a strong solution of carbonate of soda. The mixture is placed in crucibles, and kept at a good red heat until the fusion is complete. By this process regulus of antimony is pro- |

From the crucibles the metal is run into hot and greased moulds; but it is not as yet sufficiently pure to assume the crystalline form so much prized in commerce. It is remelted, with a portion of the scoriæ obtained in previous reductions, together with a certain proportion of the roasted mineral. The result of this second process is the production of an increased quantity of scoria and the purification of the metal.

Of the 65 parts of roasted sulphuret 45 parts of regulus are obtained in the first fusion, and this quantity is reduced to about 42 in the second; or, in other words, 100 parts of sulphuret of antimony, which ought to produce 73 of regulus, actually produce only 40 or 44. A portion is lost by volatilization, and another portion remains in the scoriæ. The scoria is known in commerce as crocus or kermes, and is used in veterinary medicine. It consists of sulphuret of antimony and alkaline sulphuret.

As iron combines readily with antimony, the sulphuret is sometimes reduced by heating it in contact with iron filings: as the iron tends to unite with the antimony, when in excess, an atom and a half of iron is employed to each atom of sulphuret of antimony, or 45 parts iron filings to 100 parts sulphuret of antimony.

M. Dumas states that many manufacturers keep their processes secret, which sufficiently accounts for the defective state of this branch of metallurgy; for, had they been thrown open to scientific chemists, they would have been investigated and improvea.

In some smelting-houses there is a loss of regulus amounting to 33 per cent., and a much larger expenditure of fuel than is necessary. The secret consists in giving to the surface of the ingots a beautiful stellated appearance, which the alchemists formerly regarded as a mysterious guide to the secrets of transmutation, and which is now valued in commerce as an indication of superior purity in the metal. But it is well known that when pure antimony is cooled very slowly, in a still place, the crystallization is always very beautiful; and these conditions suffice to account for an appearance the importance of which is exaggerated by the manufacturer.

Antimony combines with the other metals, and renders them brittle; and, as this effect was especially remarked in the case of gold, the alchemists distinguished it by the title of regulus, or the little king, from its power of ruling over the noble metal, and destroying its malleability. The chief alloys of antimony are type-metal, consisting of 4 lead and 1 of antimony; stereotype-metal, 6 lead and 1 antimony; music-plates, consisting of lead, tin, and antimony; Britannia-metal, consisting of 100 parts tin, 8 anti

Great Britain receives the larger portion of its supply of antimony from Singapore, which receives it from Borneo. It is imported in the shape of ore, and commonly as ballast.

ANVIL. An instrument on which malleable metals are placed during the process of hammering. Anvils are sometimes made of cast-iron, but when required to be very hard or bright they are made of wrought iron and faced with steel. In such case the core or body is prepared at the forge, by welding together a number of rude blocks of iron. When the core is rudely shaped, three square holes are made in it, one in the bottom and one at each side, for the purpose of receiving a bar of iron connected with a crane near the forge, by which the anvil is held in the fire, and turned about while being forged. The common smith's anvil consists of seven pieces :1, the core, or body; 2, 3, 4, 5, the four corners for enlarging the base; 6, the projecting end, containing a square hole for the reception of a set or chisel in cutting pieces of iron; and 7, the beak, or conical end, which is used for turning pieces of iron into a circular form, for welding hoops, &c. All these pieces are separately welded to the core. When the anvil is of large size two hearths are used, in one of which the core is raised to the welding heat and in the other the piece. They are then taken out and welded together by rapid hammering until they cohere. The whole is then heated again, and hammered until the proper shape is obtained.

The best anvils are faced with steel. This steel facing is shaped, heated, and laid on the anvil at a welding heat, the facing, however, being less heated than the anvil, and hammered rapidly until it is closely united: the whole is then finished by repeated heatings and hammerings. The anvil is next hardened by raising it, but especially the face, to a full red heat, and quenching it in a large quantity of cold water. It is of importance to cool it rapidly, and for this purpose a stream of water is to be preferred. In this process the steel facing will sometimes crack, unless it is thin. Should the hardening be successful, the facing is ground until it is perfectly even, and the edges are made sharp or round as required. When the anvil is to be used for planishing metals, it is polished with emery and crocus.

The smith's anvil is generally placed on a loose wooden block, such as the root end of an oak tree. Anvils used for cutting and for files are inserted into large blocks of stone. The more firmly the anvil is connected with the earth, the more effective is the blow of the hammer.

AQUA FORTIS. A common term, first applied by the alchemists to dilute NITRIC ACID, on account of its strong corrosive action on many animal, vegetable, and mineral substances.

AQUA REGIA. A term applied by the alchemists to a mixture of nitric and hydrochloric acids: it has the property of dissolving gold, which neither of the acids possesses separately. Two parts of hydrochloric and one of nitric acid are most effective. A partial decomposition of both acids takes place, and water, chlorine, and nitrous acid are the result. When a metal is placed in aqua regia it absorbs the chlorine, and is dissolved. This acid is the common solvent of gold and platinum.

AQUEDUCT, a conduit or channel for the conveyance of water, from the genitive case of aqua, water, and ductus, a conduit; hence the old method of spelling this word, Aquæduct, is more correct than the present. According to this derivation, any pipe or channel for the conveyance of water is an aqueduct; but the term is usually limited to those structures of masonry which are elevated above ground for the purpose of conveying a stream of water in a regular but slightly descending current across valleys and over plains.

An abundant supply of pure and wholesome water is essential to the health and prosperity of every town and city, and accordingly we find that in all ages and countries special provisions have been made to secure so desirable an object. The ruins of the aqueducts constructed in Palestine in the reign of Solomon still remain, and travellers describe the Pools of Solomon in connexion with a scheme for supplying Jerusalem with water. In the ruined cities of Central America, which still excite the astonishment of the traveller, the remains of aqueducts are also found; but of all the ancient aqueducts those of the Romans are most calculated to excite admiration, constructed as they were to pour into the city whole rivers of water for the use of the public baths, fish ponds, artificial lakes, gardens, villas, and private houses within and around the city. Some of these aqueducts extended thirty, forty, and even sixty miles from the city, in one continuous covered channel of stone, which was carried by means of arcades over the widest and deepest valleys, and by tunnels for miles through mountains and the solid rock. It is indeed a matter of painful regret that with our vastly increased engineering skill and improved means, the metropolis of a powerful nation like Great Britain should continue to languish and to suffer disease and misery, for want of an abundant supply of pure water.

Our knowledge of the aqueducts of ancient Rome is derived as well from repeated surveys of the stupendous ruins which still exist, as from a special treatise on the subject by Frontinus, who was