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of the surface to which they are to be adapted. But when other circumstances remain the same, the difficulty of bending a rope increases with the square of its diameter, as also with its tension; and it deereases according as the radius of the curvature of the body to which it is adapted increases. Of the simple mechanical pow. ers, the lever is the least subject to friction. In a wheel, the friction upon the axis is, as the weight that lies upon it, as the diameter of the axis, and as the velocity of the motion. But upon the whole, this sort of friction is not very great, provided the machine is well executed. In common pulleys, especially those of a small size, the friction is very great. It increases in proportion as the diameter of the axis increases, as the velocity increases, and as the diameter of the pully decreases. With a moveable tackle, or block of five pulleys, a power of 150 pounds will barely be able to draw up a weight of 500 pounds. The screw is subject to a great deal of friction; so much so, that the power which must be applied to it, in order to produce a given effect, is at least double that which is given by the calculation, independent of friction. But the degree of friction in the screw, is influenced considerably by the nature of the construction, for much of it is owing to the tightness of the screw, to the distance between its threads, and to the shape of the threads; the square threads producing, upon the whole, less friction than those which are sharp. The friction which attends the use of the wedge, exceeds, in general, that of any other simple mechanical power. Its quantity depends so much upon the nature of the body upon which the wedge acts, besides other circumstances, that it is impossible to give even an ap proximate estimate of it. The friction of mechanical engines not only diminishes the effect, or which is the same thing, occasions a loss of power; but is attended with the corrosion and wear of the principal parts of the machine, besides producing a considerable degree of heat, and even actual fire; it is, therefore, of great importance, in mechanics, to contrive means capable of diminishing, if not of quite removing, the effects of friction.

The methods of obtaining the important object of diminishing the friction, are of two sorts, viz. either by the interposition of particular unctuous, or oily substances between the contiguous moving parts, or by particular mechanical contrivances. Oliveoil is the best, and perhaps the only sub.

stance that can be used in small works, as in watches and clocks, when metal works against metal. But in large works the oil is liable to drain off, unless some method is adopted to confine it. Therefore for large works tallow is mostly used, or grease of any sort, which is useful for metal, as well as for wood. In the last case tar is also frequently used. The mechanical contrivances which have been made, and are in use, for the purpose of diminishing the effects of friction, consist either in avoid. ing the contact of such bodies as produce much friction, or in the interposition of rollers, viz. cylindrical bodies, between the moving parts of machines, or between mov. ing bodies in general. Such cylinders derive, from their various size and application, the different names of rollers, friction wheels, and friction rollers. Thus in millwork, and other large machines, the wooden axis of large wheels terminate in iron gudgeons, which turn in wood, or more frequently in iron or brass, which construction produces less friction than the turning of wood in wood. In the finest sort of watchwork the holes are jewelled, viz. many of the pivots of the wheels, &c. move in holes made in rubies, or topazes, or other hard stone, which, when well finished, are not liable to wear, nor do they require much oil. In order to understand the nature of rollers, and the advantage with which their use is attended, it must be considered, that when a body is dragged over the surface of another body, the inequalities of the surfaces of both bodies meet and oppose each other, which is the principal cause of the friction or obstruction; but when one body, such as a cask, a cylinder, or a ball, is rolled upon another body, the surface of the roller is not rubbed against the other body, but is only successively applied to, or laid, on the other, and is then successively lifted up from it. Therefore, in rolling, the principal cause of friction is avoided, besides other advantages: hence a body may be rolled upon another body, when the shape admits of it, with incomparably less exertion than that which is required to drag it over the surface of that other body. In fact, we commonly see large pieces of timber, and enormous blocks of stone, moved upon rollers that are laid between them and the ground, with ease and safety, when it would be almost impossible to move them otherwise.

FRICTION, is a term made use of in medicine, and implies the act of rubbing a diseased part with oils, or other substances.

Friction is also applied to the rubbing the human body with a flesh-brush, flannel, &c.; but the most important purpose of this kind of friction is for the introduction of mercury into the babit by means of the skin instead of the mouth.

FRIEND, or quaker. A society of dissenters from the church of England obtained the latter appellation in the middle of the seventeenth century; the former they had before applied, and continue to apply, to themselves. The first preacher of this society was George Fox, a man of humble birth, and illiterate. The undertaking to which he considered himself called, that of promulgating a more simple and spiritual form of Christianity than any of those which prevailed, and of directing the attention of Christians to immediate revelation, required little more reading than that of the Bible. A constant reference to the scriptures, with great zeal, courage, and perseverance, in preaching and suffering, did more than literature could have done to spread his doctrine among the middle and lower classes. The most prominent feature in the Friends' view of Christianity, is this: seeing, no man knoweth the Father but the Son, and he to whomsoever the Son will reveal him, and seeing, the revelation of the Son is in and by the Spirit; therefore the testimony of the Spirit is that alone by which the true knowledge of God is revealed. In this doctrine they agree, in substance, with the church of England, and all others who acknowledge the efficacy of grace. For in whatever way this is afforded to Christians, it is powerfully given to know and to do the will of God; and the communication of grace may be termed, in strict consistency with the sense of the New Testament, a revelation of Christ in the Spirit. The Friends receive the Holy Scriptures as having proceeded from the revelations of the Holy Spirit; they account them the secondary rule for Christians, subordinate to the word, and therefore not the word of God. According to these, they profess their belief in one God, as Father, Word, and Holy Spirit; in one Mediator, the Word made flesh, Jesus Christ; in the conception, birth, life, miracles, death, resurrection, and ascension of Jesus; and in the remission of sins thereby purchased for the whole world of fallen mankind. Christ's redemption they believe to be perfected in us by his second coming in Spirit; in which they who obey him are, through the obedience of faith, restored from their state of

alienation, and reconciled to God. They affirm, that for this end there is given to every man a measure of the light of Christ, (called by their early preachers the light within) a manifestation of the Spirit to profit withal; which discovers sin, reproves for it, leads out of it, and, if not resisted, will save from it, and lead on the Christian to perfection. In public worship they profess to wait on God in this gift, in order to have their conditions made manifest in silence and retirement of mind. They look for an extraordinary motion of it for social worship, and considering the qualification of a minister as a further gift which God confers, and of which the church ought to ju 'ge in the same spirit, they do not limit its exercise to any description of persons. They suffer some inconvenience hereby, as they acknowledge; but they prefer bearing this to the establishing of any form of worship, save the forementioned waiting in silence. They do not baptize formally, or use the sign of the communion; they say the one has ceased as to obligation, and that the true administration of the other is by the spirit alone. They deem it unlawful for Christians to swear at all; and their affirmation in civil causes is made legal instead of an oath. They refuse to "learn war, or to lift up the sword," as well as to contribute directly to military proceedings. Yet as they inculcate implicit submission, actively or passively, to Cæsar, they neither resist nor evade the legal appropriation of their substance by him, as well to these as to ecclesiastical purposes. Against the claims of the clergy, as well as many other things apparently lawful, they say in their phraseology they have a testimony to bear. Some peculiarities mark them out from their fellow citizens. Simplicity in dress, in some instances, nearly amounting to an adherence to their original, though not prescribed, costume; simplicity of language, thou to one person, and without compliments; simplicity in their manners of living; the nonobservance of fasts and feasts; the rejection of those which they call the unchristian names of days and months; and the renunciation of the theatres and other promiscuous amusements, gaming, and the usual outward signs of mourning and rejoicing, may be considered as their shibboleth. They marry anrong themselves by a ceremony or contract, religiously conducted, and bury their dead in the most simple manner. They maintain their poor, and enforce their own rules, by means of an excellent system of

discipline, founded by G. Fox. They receive approved applicants into their society by an act of monthly meeting, or particular congregation, and without subscription of articles. They disown in the same manner, after repeated admonition, not officially only, but actually extended, to offenders against morality, or their peculiar rules.

FRIEZE, FREEZE, or FRIZE, in architecture, a large flat face, or member, separating the architrave from the corniche, being that part of the entablature between the architrave and corniche. See ARCHI

TECTURE.

FRIGATE, among seamen, a ship of war, light built, and that is a good sailer. A frigate has commonly two decks, whence that called a light frigate is a frigate with only one, deck. These vessels mount from 20 to 44 guns, and make capital cruizers. Merchantmen are said to be frigate-built, when the disposition of the decks have a descent of four or five steps from the quarter-deck and forecastle into the waist, in contradistinction to those whose decks are on a continued line for the whole length of the ship, which are called galley-built. For merly the name of frigate was only known in the Mediterranean, and applied to a kind of long vessels navigated in that sea with sails and oars. Our countrymen were the first who appeared in the ocean with those ships, and equipped them for war as well as

commerce.

FRINGILLA, the finch, in natural history, a genus of birds of the order Passeres. Generic character: bill perfectly conic, slender towards the end, and extremely pointed. Many of this tribe are truly admirable, both for the elegance of their plumage, and the vivacity and melody of their song. Latham enumerates 96 species, and Gmelin 111; of which we shall notice the following: F. domestica, or the house sparrow, is never found remote from human habitations; but following the society of man, builds under the roofs of houses, and in the holes of walls, and will frequently expel the martin from its nest, to save itself the trouble of preparing one of its own. It breeds generally three times in a year. By the destruction of caterpillars, these birds are eminently serviceable; but their favourite food is grain, to procure which they are constant attendants at the barn-door, and withstanding every effort to scare them, Are every danger to partake of the of the poultry and pigeons. They icularly sagacious as well as daring,

and can, with great difficulty only, be decoyed by traps. Their sounds are harsh and grating, their dispositions irascible, and their manners intrusive. F. cœlebs, or the chaffinch, is found in this country throughout the year, and builds its nest with extreme care and neatness, lining it with hair, wool, and feathers. It is sprightly in its movements, and beautiful in its plumage; but can boast no peculiar powers of melody. The most singular circumstance attending this species of birds is, that, in some countries, the males remain all the year round, while the females are migratory to the south, returning in the spring to their former habitations and companions. Flocks composed only of females have occasionally been seen in Hampshire. This circumstance is not peculiar to these birds, but affects equally some other descriptions. It is in itself, however, not a little curious, and merits attention. F. carduelis, or goldfinch, is common in Europe, and to be found, though by no means so frequently, in Africa and Asia. It breeds twice a year, and feeds principally on seeds, and especially those of thistles, near which it prefers building its nest, which is formed with great compactness and skill. It begins to sing in April, and continues its song till the period of breeding is past. In confinement, however, it will sing for the greater part of the year. These birds are universally admired for the brilliancy of their plumage, and the melody of their sounds; and they possess, moreover, a docility which renders them particularly interesting, learning with ease a variety of ingenious movements and exercises. They are long lived, and have been known to survive the age of twenty years. Buffon mentions the case of a goldfinch which suddenly became black, and after continuing so for eight months, resumed its former sprightly and elegant colouring: this revolution was repeated at two subsequent periods. (See Aves, Plate VI. fig. 6.) F. Spinus, or the siskin, is found in various parts of Europe, generally migratory, but at irregular periods, and in very unequal numbers; the larger flights being supposed by some naturalists to occur only once in several years. It hides its nest with particular caution; and though vast numbers are to be seen on the borders of the Danube, which have not lost their original feathers, their nests have been sought, it is said, in the neighbourhood with great assiduity, but in very few instances with success. It is nearly as tractable as the goldfinch, has

great richness and variety of notes, and extraordinary power in imitating sounds. F. canaria, or canary finch. These birds constitute, to some little extent, an article of commerce, being exported from the Tyrol in considerable numbers every year to various other parts of Europe. Buffon enumerates no fewer than 29 varieties, and devotes 50 pages of his celebrated work to an interesting detail of their mauners, habits, and song. They are bred and reared in England in aviaries with great facility; and the fidelity of their attachments, and delicacy of their attentions, their extreme neatness, parental affection, and animated and almost incessant music, constitute a source of pure and exquisite entertainment to all the admirers of artless and interesting nature. F. linaria, or the linnet, is to be met with in every part of Europe, and is particularly common in England, where it builds, generally, in thorns and furze bushes, and breeds twice in the year. Linnets feed on various seeds; but particularly relish those of the flax plant, from the Latin name for which (linum) they probably derive their name. They can be taught the notes of various other birds, and even to utter words with very distinct enunciation; but their natural song, expressive of tranquillity and rapture, and poured out in a strain of richly varied melody, is infinitely superior to these unmeaning and elaborate articulations. For the red-pole and the mountain-sparrow, see Aves, Plate VI. fig. 7 and 8.

FRIT, in the glass manufacture, the matter or ingredients whereof glass is to be made, when they have been calcined or baked in a furnace; or it is the calcined matter to be run into glass. See GLASS.

FRITILLARIA, in botany, imperial fritillary, or crown imperial, a genus of the Hexandria Monogynia class and order. Natural order of Coronaria. Lilia, Jussieu. There are five species with many varieties.

FRIZING of cloth, a term in the woollen manufactory, applied to the forming of the nap of a cloth, or stuff, into a number of little hard burrs or prominences, covering almost the whole ground thereof. Some cloths are only freezed on the backside, as black cloths; others on the right side, as coloured and mixed cloths, rateens, bays, freezes, &c. Frizing may be performed two ways; one with the hand, that is, by means of two workmen, who conduct a kind of plank that serves for a frizing instrument.

The other way is by a mill, worked either by water, or a horse, or sometimes by men. This latter is esteemed the better way of frizing, by reason the motion being uniform and regular, the little knobs of the frizing are formed more equably and regularly. The structure of this useful machine is as follows:

The three principal parts are the frizer or crisper, the frizing-table, and the drawer, or beam. The two first are two equal planks or boards, each about ten feet long, and fifteen inches broad, differing only in this, that the frizing-table is lined or covered with a kind of coarse woollen stuff, of a rough sturdy nap; and the frizer is incrustated with a kind of cement composed of glue, gum arabic, and a yellow sand, with a little aquavitæ, or urine. The beam, or drawer, thus called, because it draws the stuff from between the frizer and the frizing-table, is a wooden roller, beset all over with little, fine, short points, or ends of wire, like those of cards used in carding of wool.

The disposition and use of the machine is thus the table stands immoveable, and bears or sustains the cloth to be frized, which is laid with that side uppermost on which the nap is to be raised over the table is placed the frizer, at such a distance from it as to give room for the stuff to be passed between them, so that the frizer, having a very slow semicircular motion, meeting the long hairs or naps of the cloth, twists and rolls them into little knobs or burrs, while, at the same time, the drawer, which is continually turning, draws away the stuff from under the frizer, and winds it over its own points.

All that the workman has to do while the machine is a going, is to stretch the stuff on the table, as fast as the drawer takes it off; and from time to time to take off the stuff from the points of the drawer. The design of having the frizing-table lined with stuff of a short, stiff, stubby nap, is, that it may detain the cloth between the table and the frizer long enough for the grain to be formed, that the drawer may not take it away too readily, which must otherwise be the case, as it is not held by any thing at the other end.

FROG. See RANA.

FRONDESCENTIA, in botany, a term expressive of the precise time of the year and month, in which each species of plan✩ unfolds its first leaves. All plants produce new leaves every year; but all do not re

new them at the same time. Among woody plants, the elder, and most of the honeysuckles; among perennial herbs, crocus and tulip, are the first that push or expand their leaves. The time of sowing the seed decides with respect to annuals. The oak and ash are constantly the latest in pushing their leaves the greatest number unfold them in spring; the mosses and firs in winter. These striking differences, with respect to so capital a circumstance in plants as that of unfolding their leaves, seem to indicate that each species of plant has a temperature proper or peculiar to itself, and requires a certain degree of heat to extricate the leaves from their buds, and pro duce the appearance in question. This temperature, however, is not so constant as, to a superficial observer, it may appear to be. Among plants of the same species, there are some more early than others; whether that circumstance depends, as it most commonly does, on the nature of the plants, or is owing to differences in heat, exposure, and soil. In general, it may be affirmed, that small and young trees are always earlier than larger or old ones. See GERMINATION, and Milne's Bot. Dict.

FROST, such a state of the atmosphere as causes the congelation or freezing of water or other fluids into ice. In the more northern parts of the world, even solid bodies are affected by frost, though this is only or chiefly in consequence of the moisture they contain, which being frozen into ice, and so expanding as water is known to do when frozen, it bursts and rends any thing in which it is contained, as plants, trees, stones, and large rocks. Many fluids expand by frost, as water, which expands about th part, for which reason ice floats in water; but others again contract, as quicksilver, and thence frozen quicksilver sinks in the fluid metal.

Frost, being derived from the atmosphere, naturally proceeds from the upper parts of bodies downwards, as the water and the earth: so, the longer a frost is continued, the thicker the ice becomes upon the water in ponds, and the deeper into the earth the ground is frozen. In about 16 or 17 days frost, Mr. Boyle found it had penetrated 14 inches into the ground. At Moscow, in a hard season, the frost will penetrate two feet deep into the ground: and Captain James found it penetrated 10 feet deep in Charlton Island, and the water in the same island was frozen to the depth of six feet. Sheffer assures us, that in Sweden the frost pierces

two cubits, or Swedish ells into the earth, and turns what moisture is found there into a whitish substance, like ice; and standing water to three ells or more. The same author also mentions sudden cracks or rifts in the ice of the lakes of Sweden, nine or ten feet deep, and many leagues long; the rupture being made with a noise not less loud than if many guns were discharged together. By such means however the fishes are furnished with air; so that they are rarely found dead.

The natural history of frosts furnish very extraordinary effects. The trees are often scorched and burnt up, as with the most excessive heat, in consequence of the separation of water from the air, which is therefore very drying. In the great frost in 1683, the trunks of oak, ash, walnut, &c. were miserably split and cleft, so that they might be seen through, and the cracks often attended with dreadful noises like the explosion of fire arms. Philos. Trans. Num. ber 165.

The close of the year 1708, and the beginning of 1709, were remarkable throughout the greatest part of Europe, for a severe frost. Dr. Derham says, it was the greatest in degree, if not the most universal in the memory of man; extending through most parts of Europe, though scarcely felt in Scotland or Ireland.

In very cold countries, meat may be preserved by the frost six or seven months, and prove tolerably good eating. See Captain Middleton's observations made in Hudson's Bay, in the Philos. Trans. Number 465,

sect. 2.

In that climate the frost seems never out of the ground, it having been found hard frozen in the two summer months. Brandy and spirit, set out in the open air, freeze to solid ice in three or four hours.

Lakes and standing waters, not above 10 or 12 feet deep, are frozen to the ground in winter, and all their fish perish. But in rivers where the current of the tide is strong, the ice does not reach so deep, and the fish are preserved. Id. ib.

Some remarkable instances of frost in Europe, and chiefly in England, are recorded as below; in the year

220 Frost in Britain that lasted five

months.

250 The Thames frozen nine weeks. 291 Most rivers in Britain frozen six

weeks.

359 Severe frost in Scotland for 14 weeks.

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