blow freezing. To the young and robust, therefore, frost is more pleasing than moist air; as, in the former, they are enabled to keep themselves warm by increased exercise; which, in the latter, only tends to promote and render the evaporation more severely felt on the skin. For the same reason, Dr. Darwin observes, severe and continued frosts 'destroy the children of the poor, who want both food, fire, and clothing, in this harsh climate.'

water from which it was raised, has in its compo-living_bodies, where it naturally produces a more sition an immense quantity of caloric, even more perceptible effect, than the simple contact of dry than sufficient to heat it redhot. The same may air would occasion, when it is but a few degrees be said of common salt, and of snow or ice. If a quantity of each of these substances be separately reduced to the degree of twenty-eight or thirty of Fahrenheit's thermometer, upon mixing them together, the heat, which would have raised the thermometer to that degree, now enters into their substance in such a manner, that the mercury falls down to 0. Here an excessive degree of cold is produced; and yet the substances contain the very same quantity of heat that they did before the mixture: for they absorb it from all bodies around them; and if water in a small vessel be placed in them, they will so draw out its caloric, as to reduce it to a mass of ice.

To preserve vegetable roots, as well as fruit, from the effect of cold, the following directions will be sufficient. Dry sand, and cut straw, are eminently adapted to that purpose. Potatoes, turnips, onions, &c. should be loosely placed on sand, either under or above ground, and slightly covered with cut straw or chaff: but carrots and parsneps, we are

placing them in rows or heaps, so that their tops project at the sides; being the reverse of the method followed with turnips, when packed in carts.

It seems, therefore, that the senses, even when assisted by thermometers, can only judge of the state in which the caloric is, with relation to sur-informed, may be kept during the whole winter, by rounding bodies, without regard to its quantity. Thus, if the caloric flows from any part of our bodies into any substance actually in contact with it, the sensation of cold is excited, and we call that substance cold: but if it flows from any substance I, notwithstanding these precautions, vegetables into our bodies, the sensation of heat is excited, and we call that substance hot; without regard to the absolute quantity, in either case.

The power of cold on vegetables is well known; and, though the frosts of severe winters are, on the whole, more injurious to vegetation than those of the spring; yet the latter are productive of more extensive damage, because their effects are evident almost every year. Frosts act most powerfully on ground newly cultivated, on account of the vapors continually ascending from such soil. Trees recently cut, also, suffer more than others from the spring frosts; a circumstance which must be attributed to their shooting forth with greater luxuriance. Hence, likewise, light and sandy soils are thus more frequently damaged, than firm and tough land, though both may be equally dry.

should be injured by the frost, it will be advisable, especially with frozen potatoes, to immerse them in cold water for a short time, on the approach of a thaw. By this expedient, the frosty particles are gradually extracted, and the vegetating principle is preserved, after the severest season.

On the other hand, an intense degree of cold is also attended with some good effects. Thus, aromatic spirits possess a weaker flavor, when newly distilled, than after they have been kept six or seven months, especially during the winter season. Experience has evinced, that this favorable change was produced only by the influence of cold; and M. Baume found, that by immersing quart bottles, filled with liquors, into a mixture of pounded ice and sea-salt, for six or eight hours, the spirit proves as grateful to the palate, as that which had been kept for several years. Geoffroy remarks, that simple waters also acquire a more agreeable flavor, after having been for some time exposed to the effects of cold.

Although it has been generally believed, that frost meliorates the soil, and especially clay-lands; yet, as ice contains no nitrous particles, such improvements can only be of a transitory nature, by enlarging the bulk of some moist soils, and leaving them more porous for some time after the thaw: FRUITS Are much used as an article of but, when the water has exhaled, the ground be-luxury; and from the effects they are too frequently comes as hard as before, being compressed by the incumbent weight of the air.

seen to produce, they would seem to be by no means of a salutary nature. Looseness, vomiting, Nor is the salutary influence of frosty seasons, indigestion, and even inflammation of the bowels, on the health of mankind, in the least confirmed have been seen evidently to proceed from the use by the annual bills of mortality; as many old and of various fruits. Yet it is pretty certain that the debilitated persons, whose vital heat is insufficient fault has lain not with the fruit, but with the conto excite into action their vessels, already too unsus-sumer. When fruit is eaten in large quantity, and ceptible of irritation, die in consequence of long in an unripe state; when it is forced into the stomfrosts, during severe winters. Birds, and other ach, already loaded with a plentiful dinner of soup, wild animals, as well as tender vegetables, perish meat, pudding, and all the items of a luxurious table, benumbed, from the same cause. It deserves, there is nothing wonderful in the subsequent inhowever, to be remarked, that a sharp, dry frost testine war. But when fruit is taken in modera

does not affect the human skin with that sensation tion, of a proper quantity, and at proper seasons, of chilly and piercing cold, which we experience no bad effects are to be dreaded. Fruits are eviwhen the air is loaded with moisture, the tempera-dently useful, and they are kindly sent at the very ture of which is near the freezing point. This re-season, when the systein, heated and excited by the markable difference arises from the intense degree warmth of summer, stands in need of something of cold produced by the evaporation of fluids, cooling and laxative to be taken with the food. which continually takes place on the surface of

The fruits in most common use may be classed

under the heads of stone-fruits, the apple kind, berries, (without affecting botanical accuracy in the use of this term,) and farinaceous fruits. The stone-fruits are those which are of most difficult digestion. Plums and cherries are particularly so. The ripe peach is both delicate in its flavor and easily digestible; the apricot is also very wholesome; but the nectarine is liable to disagree with some stomachs. The fruits of the apple kind are somewhat firm in their texture, and therefore rather indigestible, and liable to be detained in the stomach. Pears are rather more allowable, as their texture is softer. The white skin of the orange should be carefully rejected, but the inner pulp is grateful to all stomachs, whether in health or sickness. The fruits of the berry kind are the most wholesome of all. The strawberry or raspberry are particularly good; the grape is cooling and laxative, but the husks and seeds are to be rejected; the gooseberry is not so digestible, especially if the skin be swallowed. It is only the pulp of these fruits that is digested; the seeds always pass through the body undigested, unless they be chewed. Other berries are generally baked in pies, but the pastry should be sparingly used. The melon, a farinaceous fruit, is almost sure to disagree with weak stomachs; and when eaten after dinner, always requires abundance of salt, pepper, ginger, or other condiment to be eaten with it. Many fruits, otherwise unsafe, are much improved by cooking. Baked apples are an excellent article of food, and may even be of benefit to dyspeptic patients. Dried fruits are generally esteemed very safe, but they are apt to run into fermentation from the quantity of sugar which they contain.

FRUIT-FLIES. A name given by gardeners and others to a sort of small black flies, found in vast numbers among fruit trees in the spring season, and supposed to do great injury to them. Mr. Lewenhoeck preserved some of these flies for his microscopical observations. He found that they did not live longer than a day or two, but that the females during this time laid a great number of longish eggs. The gardeners who suppose that these flies wound the leaves of the trees are mistaken it is true that they feed on their juices; but they have no instruments wherewith they can extract these for themselves; they feed on such as are naturally extravasated; and when there is not a sufficient quantity of these for their purpose, they haunt the places to which the pucerons resort, and feed on the juices which these little creatures extravasate, by means of the holes they bore in the leaves with their trunks.

wards they were incorporated into the troops themselves, where they still retain their ancient name. As their principal office was the giving intelligence, they were often joined with the Curiosi, with whom they agreed in this part of their office.

FRUMENTATION. In Roman Antiquity, a largess of corn bestowed on the people. This practice of giving corn to the people, was very ancient among the Romans, and frequently used to soothe the turbulent humor of the populace. The number of those to whom this largess was given, was indeterminate till the time of Augustus, when it was fixed at two hundred thousand.

FUCUS. The name given by the ancients to a sea plant, from which a dye was procured, for dyeing woollen and linen cloths of that color.

FUEL. Dr. Black divides fuels into five classes; the first, comprehends the fluid inflammable bodies; the second, peat or turf; the third, charcoal of wood; the fourth, pit-coal charred; and the fifth, wood, or pit-coal, in a crude state, and capable of yielding a copious and bright flame.

The fluid inflammables are considered as distinct from the solid, on this account, that they are capable of burning upon a wick, and become in this way the most manageable sources of heat; though, on account of their price, they are never employed for producing it in great quantities; and are only used when a gentle degree, or a small quantity of heat is sufficient. The species which belong to this class are alcohol and different oils.

The first of these, alcohol, when pure and free of water, is as convenient and manageable a fuel for producing moderate or gentle heats as can be desired. Its flame is perfectly clean, and free from any kind of soot; it can easily be made to burn slower or faster, and to produce less or more heat, by changing the size or number of the wicks upon which it burns; for as long as these are fed with spirit, in a proper manner, they continue to yield flame of precisely the same strength. The cotton, or other materials, of which the wick is composed, is not scorched or consumed in the least, because the spirit with which it is constantly soaked is incapable of becoming hotter than one hundred and seventy-four degrees, Fahrenheit, which is considerably below the heat of boiling water. It is only the vapor that arises from it which is hotter, and this too only in its outer parts, that are most remote from the wick, and where only the combustion is going on, in consequence of communication and contact with the air. At the same time, as the alcohol is totally volatile, it does not leave any fixed

FRUMENTARII. A kind of soldiers or arch-matter which, by being accumulated on the wick, ers under the western empire. The first mention might render it foul and fill up its pores. The we find made of these officers is in the reign of wick, therefore, continues to imbibe the spirit as the emperor Adrian, who made use of them to in- freely, after some time, as it did at the first. These form himself of whatever passed. They did not are the qualities of alcohol as a fuel. But these make any particular corps distinct from the rest of qualities belong only to a spirit that is very pure. the forces, but there was a certain number of them If, on the contrary, it be weak, and contain water, in each legion. It is supposed that they were at the water, being less volatile, does not evaporate so first a number of young persons, disposed by Au- fast from the wick as the more spirituous part; and gustus throughout the provinces, particularly on all the wick becomes, after some time, so much soaked the grand roads, to acquaint the emperor, with all with water that it does not imbibe the spirit propexpedition, of every thing that happened. After-erly. The flame becomes much weaker, or is

altogether extinguished. When alcohol is used as a fuel, therefore, it ought to be made as strong, or free from water, as possible.

coal. 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 redhot in the centre, and, if opened in this state, would instantly burn with fury.

the whole pile in a very short time. It would burst out into a blaze, and be quickly consumed to ashes, were it not covered all over with earth, or Oil, although fluid like spirit of wine, and capa- clay, beaten close, leaving openings at all the spible of burning in a similar manner, is not so con- racles. These are carefully watched; and, whenvenient in many respects. It is disposed to emit ever the white watery smoke is observed to be soot; and this applying itself to the bottom of the succeeded by thin blue, and transparent smoke, the vessel exposed to it, and, increasing in thickness, whole is immediately stopped; this being the indiforms, by degrees, a soft and spongy medium, cation of all the watery vapor being gone, and the through which heat is not so freely and quickly burning of the true coaly matter commencing. transmitted. This was observed by Muschenbroeck Thus is a pretty strong red heat raised through the in his experiments upon the expansions of metal- whole mass, and all the volatile matters are dissiline rods heated by lamps. It is true we can pre-pated by it, and nothing now remains but the charvent this entirely, by using very small wicks, and increasing the number, if necessary, to produce the heat required. Or, we may employ one of those lamps, in which a stream of air is allowed to rise through the middle of the flame, or to pass over its surface with such velocity as to produce a more complete inflammation than ordinary. But we shall be as much embarrassed in another way, for the oils commonly used, being capable of assuming a heat greatly above that of boiling water, scorch and burn the wick, and change its texture, so that it does not imbibe the oil so fast as before. Some have attempted a remedy, by making the wick of incombustible materials, as asbestos, or wire; but still, as the oil does not totally evaporate, but leaves a small quantity of gross fixed carbona-bustible matter in greater quantity, or in a more ceous matter, this, constantly accumulating, clogs the wick to such a degree, that the oil caunot ascend, the flames become weaker, and, in some cases, are entirely extinguished. There is, however, a difference among the different oils in this respect; some being more totally volatile than others. But the best are troublesome in this way, and the only remedy is to change the wicks often, though we can hardly do this and be sure of keeping always an equal flame.

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 comcondensed 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 consuines, 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 do 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.

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.

The second kind of fuel mentioned, peat, is so spongy that, compared with the more solid fuels, it is unfit to be employed for producing very strong beats. It is too bulky for this: we cannot put into a furnace, at a time, a quantity that corresponds with the quick consumption that must necessarily go on when the heat is violent. There is, no doubt, a great difference in this respect among different kinds of this fuel; but this is the general character of it. However, when we desire to produce and keep up, by means of cheap fuel, an extremely mild, gentle heat, we can hardly use any thing better than peat. But it is best to have it previously | charred, that is, scorched, or burnt to black coal. The advantages gained by charring have been fully ascertained. When prepared for use in that manner, it is capable of being made to burn more Flaming fuel cannot be managed like the charslowly and gently, or will bear without being ex- coals. If little air be admitted, it gives no flame, tinguished altogether, a greater diminution of the but sooty vapor, and a diminution of heat. And quantity of air, with which it is supplied, than any if much air be admitted to make those vapors other of the solid fuels. Dr. Boerhaave found it break out into flame, the heat is too violent. These extremely convenient and manageable in his Fur-flaming fuels, however, have their particular uses, nus Studiosorum. for which the others are far less proper. For it is The next fuel, in order, is the charcoal of wood. a fact, that flame, when produced in great quantity, This is prepared by piling up billets of wood into a pyramidal heap, with several spiracles, or flues, formed through the pile. Chips and brushwood are put into those below, and the whole is so constructed that, when kindled, it kindles almost over

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 vapor, gives a most intense heat. This proceeds from the

It

vaporous nature of flame, and the perfect misci- | soft, grayish, brown, dense, and heavy marle. bility of it with the air. When dry, it is of a grayish, ash-colored brown, in all degrees from very pale to almost black; and it has generally something of a greenish cast. 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.

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 vapor 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 consequence 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.

FULLING. The art or act of scouring and pressing cloths, and other woollen manufactures, to cleanse, thicken, and render them more firm and strong, which is done by means of a water-mill.

The

FULMINANS, PULVIS. Is a composition of three parts of nitre, two parts of pulverised pearlash, and one part of flowers of sulphur. parts are to be well mixed in an earthen mortar, and placed on a tile or plate before the fire till it is perfectly dry; and if it be transferred while hot, into a bottle with a ground stopper, it may be kept for any time without injury. Its effects are exhibited by pouring from ten to forty grains into an

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 in-iron ladle, placed over a slow fire, in which case it convenient. 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 earthen 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 interstices, 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 vapor 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.

FULCRUM. The centre of motion in mechanical combinations, and the name of the prop on which a lever works; but every mechanical arrangement has such a centre, whether visible or

not.

The forces, or momentum on each side the fulcrum of a balanced lever, are always equal. Thus, the sun and planets have a centre of momentum, or fulcrum, round which they move. The earth and moon, also, move round a common centre, or fulcrum. In machines and solid levers, the arms are as the simple distances, but in gases, as the squares of the distances.

will soon acquire a brown color, and the consistence of paste; a blue lambent flame will appear on its surface; and immediately afterwards the whole composition will explode with a slight mo|mentary flash, and a loud noise. The mass being removed from the fire as soon as it is fused, may be kept in a dry, well closed phial, and it will at any time be exploded by a spark, and hum like gunpowder, but more rapidly and with a greater detonation; but this effect cannot be produced in the unmelted powder, however accurately its ingredients may have been mixed. Whilst the powder is in fusion, but not sufficiently heated to produce the blue flame, a particle of ignited charcoal thrown upon it, will immediately occasion a very loud explosion. The fulminating property of this powder is acquired by fusion, or when the potash and sulphur form sulphuret of potash. It may therefore be prepared by mixing sulphuret of potash with nitre, instead of adding the sulphur and alkali separate.

FULMINATION. The noise which some minerals or metals make when heated in a crucible; as fulminating powder, which is made of nitre, potash, and the flowers of sulphur, triturated in a warm mortar. If this powder be fused in a ladle, and then set on fire, it will explode with a noise like thunder. If a solution of gold be precipitated by ammonia, the product will be fulminating gold, a grain of which, if held over a flame, will explode with a sharp, loud noise.

FUMIGATION. In Medicine, signifies the mutation of different fumes, for the relief of catarrhs, coughs, sore throats, &c. The term is also applied to the process of fumigating rooms during the prevalence of contagious disease.

If it be true that contagious diseases are derived from the presence of some elastic fluid existing in the atmosphere, which has been called miasma, and since these, of which there must be varieties, FULLER'S EARTH. In Natural History, al as well as the disagreeable odors resulting from