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this being the indication of all the watery vapour being gone, and the burning of the true coaly matter commencing. Thus is a pretty strong red heat raised through the whole mass, and all the volatile matters are dissipated by it, and nothing now remains but the charcoal. The holes being all stopped in succession, as this change of the smoke is observed, the fire goes out for want of air. The pile is now allowed to cool. This requires many days; for, charcoal being a very bad conductor of heat, the pile long remains red hot in the centre, and, if opened in this state, would instantly burn with fury.

Small quantities may be procured at any time, by burning wood in close vessels. Little pieces may be very finely prepared, at any time, by plunging the wood in lead melted and red hot.

This is the chief fuel used by the chemists abroad, and has many good properties. It kindles quickly, emits few watery or other vapours while burning, and when consumed leaves few ashes, and those very light. They are, therefore, easily blown away, so that the fire continues open, or pervious to the current of air which must pass through it to keep it burning. This sort of fuel, too, is capable of producing as intense a heat as can be obtained by any; but in those violent heats it is quickly consumed, and needs to be frequently supplied.

Fossil coals charred, called cinders, or coaks, have, in many respects, the same properties as charcoal of wood; as kindling more readily in furnaces than when they are not charred, and not emitting watery, or other gross smoke, while they burn, This sort of charcoal is even greatly superior to the other in some properties.

It is a much stronger fuel, or contains the combustible matter in greater quantity, or in a more condensed state. It is, therefore, consumed much more slowly on all occasions, and particularly when employed for producing intense melting heats. The only inconveniences that attend it are, that, as it consumes, it leaves much more ashes than the other, and these much heavier too, which are, therefore, liable to collect in such quantity as to obstruct the free passage of air through the fire; and further, that when the heat is very intense these ashes are disposed to melt or vitrify into a tenacious drossy substance, which clogs the grate, the sides of the furnace and the vessels. This last inconvenience is only troublesome, however, when the heat required is very

intense. In ordinary heat the ashes de not melt, and though they are more copious and heavy than those of charcoal of wood, they seldom choke up the fire considerably, unless the bars of the grate be too close together.

This fuel, therefore, is preferable, in most cases, to the charcoal of wood, on account of its burning much longer, or giving much more heat before it is consumed. The heat produced, by equal quantities, by weight of pit-coal, wood-charcoal and wood itself, are nearly in proportion of 5, 4, and 3. The reason why both these kinds of charcoal are preferred, on most occasions, in experimental chemistry, to the crude wood, or fossil coal, from which they are produced, is, that the crude fuels are deprived, by charring, of a considerable quantity of water, and some other volatile principles, which are evaporated during the process of charring, in the form of sooty smoke or flame. These volatile parts, while they remain in the fuel, make it unfit (or less fit) for many purposes in chemistry. For besides obstructing the vents with sooty matter, they require much heat to evaporate them; and therefore, the heat of the furnace, in which they are burnt, is much diminished and wasted by every addition of fresh fuel, until the fresh fuel is completely inflamed, and restores the heat to its former strength.

But these great and sudden variations of the heat of a furnace are quite inconvenient in most chemical processes. In the greater number of chemical operations, therefore, it is much more convenient to use charred fuel, than the same fuel in its natural state.

There are, at the same time, some kinds of fossil coal, which are exceptions to what has now been delivered in general. We meet with some of them that leave a smaller proportion of ashes than others, and the ashes of some are not so liable to melt in violent heats. There is one species too, such as the Kilkenny coal of Ireland, and which occurs likewise in some parts of this country, that does not contain any sensible quantity of water, or other such volatile principles. But this may be called a sort of native charcoal. It has the appearance of ordinary coal, but, when thrown into the fire, does not emit smoke or soot. It merely becomes red, gives a subtile blue flame, and consumes like charcoal; only it lasts surprizingly long, or continues to give heat for a very long time before it

is totally consumed. But it cannot be made to burn so as to produce a gentle heat. If not in considerable quantity, and violently heated, it is soon extinguished.

In using this kind of fuel, it is proper to be on our guard against the dangerous nature of the burnt air, which arises from charcoal of all kinds. Charcoal burns without visible smoke. The air arising from it appears to the eye as pure and as clear as common air. Hence it is much used abroad by those who are studions of neatness and cleanliness in their apartments. But this very circumstance should make us more watchful against its effects, which may prove dangerous, in the highest degree, before we are aware of it. The air arising from common crude fuel is no doubt as bad, but the smoke renders it disagreeable before it become dangerous. The first sensation is a slight sense of weakness; the limbs seem to require a little attention, to prevent falling. A slight giddiness, accompanied by a distinct feeling of a flush, or glow in the face and neck. Soon after, the person becomes drowsy, would sit down, but commonly falls on the floor insensible of all about him, and breathes strong, snoring as in an apoplexy, If the person is alarmed in time, and escapes into the open air, he is commonly seized with a violent head-ach, which gradually abates.

But when the effect is completed, as above described, death very soon ensues, unless relief be obtained. There is usually a foaming at the mouth, a great flush or suffusion over the face and neck, and every indication of an oppression of the brain, by this accumulation of blood. The most successful treatment is to take off a quantity of blood immediately, and throw cold water on the head repeatedly. A strong stimulus, such as hartshorn, applied to the soles of the feet, has also a very good effect.

The fifth and last kind of fuel is wood, or fossil coals, in their crude state, which it is proper to distinguish from the charcoals of the same substances. The difference consists in their giving a copious and bright flame, when plenty of air is admitted to them, in consequence of which they must be considered as fuels very different from charcoal, and adapted to different purposes. See FLAME.

Flaming fuel cannot be managed like the charcoals. If little air be admitted, it gives no flame, but sooty vapour, and a

diminution of heat. And if much air be admitted to make those vapours break out into flame, the heat is toe violent. These flaming fuels, however, have their particular uses, for which the others are far less proper. For it is a fact, that flame, when produced in great quantity, and made to burn violently, by mixing it with a proper quantity of fresh air, by driving it on the subject, and throwing it into whirls and eddies, which mix the air with every part of the hot vapour, gives a most intense heat. This proceeds from the vaporous nature of flame, and the perfect miscibility of it with the air.

As the immediate contact and action of air is necessary to the burning of every combustible body; so the air, when properly applied, acts, with far greater advantage on flame, than on the solid and fixed inflammable bodies: for when air is applied to these last, it can only act on their surface, or the particles of them that are outermost; whereas flame being a vapour or elastic fluid, the air, by proper contrivances, can be intimately mixed with it, and made to act on every part of it, external and internal, at the same time. This great power of flame which is the conquence of this, does not appear when we try small quantities of it, and allow it to burn quietly, because the air is not intimately mixed with it, but acts only on the outside, and the quantity of burning matter in the surface of a small flame is too small to produce much effect.

But when flame is produced in large quantity, and is properly mixed and agitated with air, its power to heat bodies is immensely increased. It is therefore peculiarly proper for heating large quantities of matter to a violent degree, especially if the contact of solid fuel with such matter is inconvenient. Flaming fuel is used for this reason in many operations performed on large quantities of metal, or metallic minerals, in the making of glass, and in the baking or burning of all kinds of earthern ware. The potter's kiln is a cylindrical cavity, filled from the bottom to the top with columns of wares, the only interstices are those that are left between the columns ; and the flame, when produced in sufficient quantity, proves a torrent of liquid fire, constantly flowing up through the whole of the insterstices, and heats the whole pile in an equal manner.

Flaming fuel is also proper in many works or manufactories, in which much fuel

is consumed, as in breweries, distilleries, and the like. In such works, it is evidently worth while to contrive the furnaces so that heat may be obtained from the volatile parts of the fuel, as well as from the fixed; for when this is done, less fuel serves the purpose than would otherwise be necessary. But this is little attended to, or ill understood in many of those manufactories. It is not uncommon to see vast clouds of black smoke and vapour coming out of their vents. This happens in consequence of their throwing too large a quantity of crude fuel, into the furnace at once. The heat is not sufficient to inflame it quickly, and the consequence is a great loss of heat. See LABORATORY.

FUGUE, in music, signifies a composition, in which one part leads off some determined succession of notes called the subject, which after being answered in the fifth and eighth by the other parts, is interspersed through the movement, and distributed amid all the parts in a desultory manner at the pleasure of the composer. There are three distinct descriptions of fugues, the simple, which contains but one subject; the double, that which consists of two subjects; and the counter fugue, is that in which the subjects move in a direction contrary to each other.

FUIRENA, in botany, so named in memory of George Fuiren, a genus of the Triandria Monogynia class and order. Natural order of Calamariæ. Cyperoideæ, Jussieu. Essential character: ament imbricate, with awned scales; calyx none; corolla with three-petal shaped obcordate glumes, ending in a tendril. There is but one species, viz. F. paniculata, a lofty grass. Native of Surinam and Jamaica.

FULCRUM, in mechanics, the prop or support, by which a lever is sustained. See MECHANICS.

FULGORA, in natural history, lanternfly, a genus of insects of the order Hemiptera. Head hollow, inflated, extended for ward; antennæ short, seated beneath the eyes, consisting of two joints, the outer one larger and globular; snout elongated, inflected, four-jointed; legs formed for walking. There are about 25 species, almost inhabitants of hot climates. Mr. Donovan has described the F. Europæa; the body of which is green; wings hyaline, reticulate; front conic. This is a small insect, and destitute of the shining quality, by which foreign species are distinguished. But the F. lanternaria, or Peruvian lantern

fly is one of the most curious of insects, it is three inches long, and the breadth between the tips of the expanded wings is about five or six inches. This beautiful insect is a native of Surinam and other parts of South America, and during the night it diffuses so strong a phosphoric splendor from its head, which is nearly as large as the rest of the body, that it may be employed for the purpose of a candle or torch.

FULICA, the gallinule and the coot, in natural history, a genus of birds of the order Gralla. Generic character: bill strong, thick, and sloping to the point; upper mandible arched over the lower at the edge, and reaching far up the forehead; nostrils nearly oval; front bald; toes four, long and furnished with broad scalloped membranes. There are twenty-five species.

F.atra-coot, is distinguished from the galli. nule by pinnated feet. It inhabits Europe, Asia, and America, and is about the size of a small fowl. It feeds on small fish and water-insects, is common in some parts of this country at all seasons, but in the breeding season is seen almost always in pairs, about the borders of ponds and lakes well fringed with rushes, of which it mats itself a large nest, said to be often observed floating on the water. These birds are devoured when young by the buzzards, which infest their haunts, and prevent them from that great multiplication which might be otherwise expected. Rallus crex, or the crake gallinule, is found in various parts of Europe, and is particularly abundant in Ireland, where it is supposed by Latham to winter. Wherever quails are, the crake is to be met with. It runs fast, but flies with great awkwardness, with its legs hanging down. Its food is grain and insects. On its arrival in England, where it is migratory, it is poor and emaciated, but fattens afterwards with great rapidity, and is esteemed excellent for the table. Its full weight is about eight ounces.

F. porphyrio or the purple water hen, occurs in almost all the warmer latitudes of the globe. It is of the size of a fowl; in Sicily is kept merely for its beauty, and in Persia exhibits its greatest elegance of plumage. It is tamed with great ease, and will feed very quietly in the farm-yard on grain or roots, but is particularly fond of fishes, which it plunges in the water before it takes them to its mouth. Standing on one leg it employs the other as a hand in many cases, particularly in lifting its food

to its mouth, in the same manner as a par dually in bulk, and falls into a fine soft

rot.

F. chloropus, or the common water-hen, is found in various parts of England, haunting the borders of ponds and rivers, which abound in weeds, and breeding twice in a season. It flies aukwardly, but runs and swims well. Its flesh is thought excellent, and its general weight is about fifteen ounces. Rallus Carolinus, or the American water-hen, is as large as a quail. In the beginning of autumn these birds are found in Virginia in extreme abundance. From a state of perfect leanness they speedily become so fat as to be incapable of flying, and are knocked off the reeds of the marshes by the paddles of the Indians, who make pleasurable excursions in their canoes for this purpose, and in the course of one night a party will take ten or twelve hundred of them. They are extremely admired for food, and supply part of the daily repast of every planter during their short season. Rallus parzana, or the spotted gallinula, is found in Cumberland, and supposed to be migratory. It is fond of solitude, and unless in breeding time, almost always alone. Its haunts are similar to those of the common water-hen. Its nest is built in the form of a boat, and tied or fixed to reeds to prevent its being carried off by the water. Its young run as soon as they are hatched. For the great coot, see Aves, Plate VII. fig. 4.

FULIGO, in botany, a genus of the Cryptogamia Fungi class and order. Fungus with a cellular fibrous bark; the fibres penetrating in a reticulate manner through the seminal mass.

FULLER, a workman employed in the woollen manufactories, to mill, or scour, cloths, serges, and other stuffs, in order to render them more thick, compact, and durable.

FULLER's earth, in natural history, a soft, greyish, brown, dense, and heavy marle : when dry, it is of a greyish, ash-coloured brown, in all degrees from very pale to almost black, and it has generally something of a greenish cast: it is very hard and firm, of a compact texture, of a rough and somewhat dusty surface, that adheres slightly to the tongue: it is very soft to the touch, not staining the hands, nor breaking easily between the fingers: it has a little harshness between the teeth, and melts freely in the mouth thrown into water, it makes no ebullition, or hissing, but swells gra

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Fuller's earth is not now in so much request in the country as it was formerly, owing to the almost general use of soap. In England it is found in beds, covered by, and resting upon, that peculiar sand-stone formation, which accompanies and serves as the foundation to chalk: its colour is yellowish grey, with a faint tinge of green. It is found in Hampshire, Bedfordshire, and in Surrey.

FULLING, the art or act of cleansing, scouring, and pressing cloths, stuffs, and stockings, to render them stronger, closer, and firmer; called also milling. The fulling of cloths and other stuffs is performed by a kind of water-mill, thence called a fulling or scouring-mill. These mills, except in what relates to the mill-stones and hopper, are much the same with corn-mills: and there are even some which serve indifferently for either use; corn being ground, and cloths fulled, by the motion of the same wheel. Whence in some places, particu larly in France, the fullers are called millers; as grinding corn and milling stuffs at the same time. The method of fulling cloths and woollen stuffs with soap is this: a coloured cloth is to be laid in the usual manner in the trough of a fulling mill, without first soaking it in water, as is commonly practised in many places. To full this trough of cloth, 15 pounds of soap are required, one half of which is to be melted in two pails of river or spring water, made as hot as the hand can well bear it. This solution is to be poured by little and little upon the cloth, in proportion as it is laid in the trough; and thus it is to be fulled for at least two hours; after which it is to be taken out and stretched. This done, the cloth is immediately returned into the same

trough, without any new soap, and then fulled two hours more. Then taking it out, they wring it well, to express all the grease and filth. After the second fulling, the remainder of the soap is dissolved as in the former, and cast four different times on the cloth, remembering to take out the cloth every two hours to stretch it, and undo the plaits and wrinkles it has acquired in the trough. When they perceive it sufficiently fulled, and brought to the quality and thickness required, they scour it in water, keeping it in the trough till it is quite clean. As to white cloths, as these full more easily and in less time than coloured ones, a third part of the soap may be spared.

FULMINATION, in chemistry, differs from detonation only in degree, they are both the effects of rapid decomposition accompanied by a loud noise, either with or without flame. See GOLD, MERCURY, POWDER, SILVER.

FUMARIA, in botany, English fumitory, a genus of the Diadelphia Hexandria class and order. Natural order of Corydales. Papaveraceæ, Jussieu. Essential character: calyx two-leaved; corolla ringent; filaments two, membranaceous, with three anthers on each. There are fifteen species.

FUMIGATION, in medicine, a process by means of which the nitrous and other mineral acids, in a state of vapour, is dispersed through the apartments of those who lie sick of infectious fevers. This method of destroying contagion, in crowded places, was first brought into practice by Dr. Carmichael Smyth, who having given some striking proofs of its efficacy received a reward from parliament. When this fumigation is undertaken on board ships, the ports and scuttles are closed, a number of pipkins, containing hot sand, are procured, and into each is plunged a small tea cup, containing half an ounce of sulphuric acid. As soon as the acid is properly heated an equal quantity of pulverised nitre is added, and the mixture stirred with a glass rod. The vapour resulting from the decomposition of nitre ascends, and is by the nurses conducted to every part of the apartment, which not only abates the malignity of the fever, but effectually stops the progress of infection. In a late volume of the "Annales de Chemie," we have some striking facts of the efficacy of fumigation, according to the method of M. Guyton de Morveau, who makes use of sulphuric acid, sea-salt, and manganese. It has been tried, and com

pletely succeeded in stopping the progress of the rot among sheep: it has destroyed the putrid odours arising from meat in the worst possible state, as well as having been eminently successful in the cure of the most alarming fevers, and preventing the effects of contagion.

FUNARIA, in botany, a genus of the Cryptogamia Musci class and order. Capsule obovate; fringe double; outer, of 16 oblique wedge-form teeth, cohering at the tips; inner, a membrane divided into 16 flat teeth; veil square. There are three species.

FUNCTION, in algebra, denotes any compound quantity; and when one of the component quantities is variable it is said to be a variable function.

Functions are formed either by addition, subtraction, multiplication, division, involution, or evolution; as also by the resolution of equations. But besides these, which are called algebraical functions, there are others called transcendental, arising from the management of exponents, logarithms, &c.

FUNDS, public, the taxes or other public revenues appropriated to the payment of the interest or principal of the national debt. When the expedient of borrowing large sums for the public service was first adopted, it was found necessary to set apart and assign to the lender the produce of some branch of the revenue supposed to be adequate to the payment of the interest or principal, or both, according to the terms of the contract; each loan had thus a separate fund provided for it, which was usually distinguished by the date of the transaction, the rate per cent. payable, or some circumstance relating to the mode of raising the money or the purpose to which it was to be applied. These separate funds sometimes produced more than the yearly payments with which they were charged, but more frequently fell short of them, and as making good the deficiencies of some, from the surpluses of others, or from the current supplies, created much trouble and useless intricacy in the management of the public finances, it was found more convenient to combine several of the funds, and to charge the payments for which they had been set apart on the aggregate produce of the several duties. It then became necessary to give a more general denomination to the fund; and thus have been established, at different periods, the Aggregate

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