a general name, by which men seem to understand a certain sensation or complex notion of light, heat, burning, melting, &c.

The power of fire is so great, its effects so extensive, and the manner of its acting so wonderful, that some of the wisest nations of old reverenced and worshipped it, as the supreme deity. Some of the chemists also, after they had discovered its surprising operations, suspected it to be an uncreated being: and indeed the most famous of them have acknowledged it as the source of all their knowledge; and hence have professed themselves philosophers by fire, nor thought they could be honoured with a nobler title. Now, amongst all the wonderful properties of fire, there is none more extraordinary than this, that though it is the principal cause of almost all the sensible effects that continually fall under our observation, yet it is itself of so infinitely a fugitive nature, that it illudes the most sagacious enquiries, nor ever comes within the cognizance of our senses. Fire is generally divided into three kinds or species, viz., celestial, subterraneous, and culinary.

By celestial fire is principally understood that of the sun, without regard to that of the fixed stars, though this perhaps may be of the same nature.

By subterraneous fire we understand that which manifests itself in fiery eruptions of the earth, volcanoes, or burning mountains; or by any other effects it produces in mines, or the more central parts of the earth.

By culinary fire we mean that employed in all chemical operations, and the common occasions of life.

The sun's heat appears to be the adverting principle, or general-instrument of all the operations in the animal, vegetable, atmospherical, marine, and mineral kingdoms.

Fire, considered in itself, seems to exist in the greatest purity and perfection in the celestial regions; at least we are insensible of any considerable smoke it yields; yields: for the rays of light come to us from the sun, unmixed with any of that grofs, succulent, or terrestrial matter, found in culinary and subterranean fires; but, allowing for this difference, the effects of the solar fire appear the same as those of culinary fire.

If we examine the effects of subterranean fires, we shall find them the same with those produced by culinary fire. Thus, burnt coals, cinders, and melted minerals, are thrown up by Vesuvius and other burning mountains. Warm nephritical exhalations, natural hot springs, steams, vapours, smoke, &c. are found in several parts of the globe, rising nearly in the same manner as if they were produced by the heat of a furnace. Whence it appears, that subterraneous fires are of the same nature with the culinary.

As men generally affix to the word fire, a complex idea of burning, light, heat, melting, &c., this idea should be analysed, in order to see what parts are essential, and what precarious or arbitrary.

We frequently find the effects of fire, produced where no visible fire appeared. Thus the fingers are easily burnt by an iron heated below the degree of ignition, or so as to be no ways visibly red-hot or fiery: whence it follows, that the eye is no judge of fire.

So likewise the touch gives no positive notice of any degree of fire below the natural heat of the body, or any so great as to destroy the organ.

Again, the effects of fire are often produced without any manifest signs of burning, melting, &c. as in evaporations, &c. If this method of exclusion and rejection were pursued to its due length, we should perhaps find no criterion, infallible mark, or characteristic of fire in general, but that of a particular motion struggling among the minute parts of bodies, and tending to throw them off at the surface. If this should prove the case, then such a motion will be the form and essence of fire; and which, being present, makes fire also present; and, when absent, makes fire also absent: whence to produce fire, and produce this motion in bodies, will be one and the same thing.

The great and fundamental difference in respect to the nature of fire is, whether it be originally such, formed thus by the Creator himself at the beginning of things; or whether it be mechanically producible from other bodies, by inducing some alterations in the particles thereof. The former opinion is maintained by Homberg, Boethaeve, the younger Lemery, and s'Gravefande; the latter is chiefly supported by the English philosophers, Lord Bacon, Mr Boyle, and Sir Isaac Newton.

Bacon, in the treatise De Forma Calicli, deduces, from a great number of particulars, that heat in bodies is no other than motion so and so circumstanced; so that to produce heat in a body, nothing is required but to excite a certain motion in the parts thereof.

Boyle seconds him in an express treatise of the mechanical origin of heat and cold, and maintains the same doctrine with new observations and experiments; as a specimen of which, we shall hear give the two following.

1. In the production of heat, says that able philoso- This last sentiment falls in with that of Boerhaave and the celebrated M. Musschenbroek. But notwithstanding what those able philosophers have advanced, it is evident that fire, heat, flame, &c., are only the different modifications of the particles of light, and that the particles of light themselves depend entirely on velocity for their lucid quality; hence, by many experiments, we know, that the particles of bodies become lucid, or particles of light, by only producing in them a requisite degree of velocity: thus the particles in a rod of iron, being hammered very nimbly, shine and become red-hot: thus also the violent stroke of the flint against the steel, in striking fire, puts the particles of the steel, which it takes off, into such a motion as causes them to melt, and become red-hot, which makes the sparks of fire produced by each stroke: as, therefore, fire consists in the great velocity of the particles, so it may be communicated from one body in which it is, to another in which it is not, after the same manner that one body in motion will communicate motion to another that has got none.

Fire differs from heat only in this, that heat is a motion in the particles of a body, with a lesser degree of velocity; and fire, a motion with a greater degree of velocity, viz. such as is sufficient to make the particles shine; though we often call such a state as will burn, fire, though it does not actually shine; and we seldom call those lucid bodies fires, which only shine, and do not burn. These are a sort of phosphori, which, though they have no heat, yet seem to owe their lucidity to the motion of their parts.

There seems to be no other difference between fire and flame, than this; that fire consists in a glowing degree of velocity in the parts of a body, while yet subsisting together in the mass; but flame is the same degree of velocity in the particles dissipated and flying off in vapours: or, to use Sir Isaac Newton's expression, flame is nothing else but a red-hot vapour. See Flame.

chemistry. See Chemistry, p. 67 and 110.

Electrical Fire. See Electricity.

Walking Fire, in meteorology. See Will-with-a Whisp.

theology. See Hell.

We read of the sacred fire in the first temple of Jerusalem, concerning which the Jews have a tradition that it came down from heaven: it was kept with the utmost care, and it was forbidden to carry any strange fire into the temple. This fire is one of the five things which the Jews confess were wanting in the second temple.

The Pagans had their sacred fires, which they kept in their temples with the most religious care, and which were never to be extinguished. Numa was the first who built a temple to Fire as a goddess, at Rome, and instituted an order of priestesses for the preservation of it. See Vestals.

Fire was the supreme god of the Chaldæans; the magi were worshippers of fire; and the Greeks and Armenians still keep up a ceremony called the Holy Fire, upon a persuasion that every Easter-day a miraculous fire descends from heaven into the holy sepulchre, and kindles all the lamps and candles there.

Fire-lock. See Gun, Musquet, &c.

Fire pots, in the military art, small earthen pots, into which is put a charged grenade, and over that powder enough till the grenade is covered; then the pot is covered with a piece of parchment, and two pieces of match across lighted: this pot being thrown by a handle of matches where it is designed, it breaks and fires the powder, and burns all that is near it, and likewise fires the powder in the grenade, which ought to have no fuse, to the end its operations may be the quicker.

Fire-works. See Pyrotechnia.

Fire ship, in the navy, a vessel charged with artificial fire-works, which having the wind of an enemy's ship, grapples her, and sets her on fire.

Fire-office, an office of insurance from fire. See Assurance.

Wild-Fire, a kind of artificial or factitious fire, which burns even under water, and that with greater violence than out of it. It is composed of sulphur, naphtha, pitch, gum, and bitumen; and is only extinguishable by vinegar mixed with sand and urine, or by covering it with raw hides. Its motion or tendency is said to be contrary to that of natural fire, and it always follows the direction in which it is thrown, whether it be downwards, sideways, or otherwise.

Firing-iron, in farriery, an instrument not unlike the blade of a knife; which being made red-hot, is applied to a horse's hams, or other places standing in need of it, as in preternatural swellings, farcy, knots, &c., in order to disperse them.