FIR-TREE, in botany. See ABIES.
FIRE is that subtle, invisible, substance, by which all bodies are expanded, or enlarged in their dimensions, and then become hot to the touch; fluid substances of every kind are carried off in vapour; solid bodies become luminous, and are likewise dissipated in vapour, or, if incapable of being evaporated, become fluid, and at last are converted into glass. It seems likewise to be the chief agent in nature, on which animal and vegetable life have an immediate dependence, and without which it doth not appear that the system of nature itself could subsist a single moment.
No question in natural philosophy seems more difficult to be resolved than that concerning the nature of fire, and none has been more agitated. One set of philosophers, amongst whom are Lord Bacon, Mr Boyle, Sir Isaac Newton, &c. assert, that fire is not any substance of itself distinct from terrestrial bodies, but that it consists only in a vehement vibratory motion of their parts. Hence, Lord Bacon defines heat, by which he means fire itself, to be "an expansive undulatory motion in the minute particles of a body, whereby they tend with some rapidity towards the circumference, and at the same time tend a little upwards." From this he infers, that if in any natural body you can excite a motion whereby it shall expand or dilate itself, and can repress and direct this motion upon itself, in such a manner, that the motion shall not proceed uniformly, but obtain in some parts and be checked in
others, you will generate heat, or fire.
To the same purpose Mr Boyle argues in a treatise on the mechanical origin of heat and cold. "In the production of heat, (says he,) there appears nothing on the part either of the agent or patient, but motion, and its natural effects. When a smith briskly hammers a small piece of iron, the metal thereby becomes exceedingly hot: yet there is nothing to make it so, except the forcible motion of the hammer impressing a vehement and variously determined agitation on the small parts of the iron; which, being a cold body before, grows, by that superinduced commotion of its small parts, hot—first, in a more loose acceptance of the word, with regard to some other bodies with which it was cold before: then sensibly hot, because this agitation exceeds that of the parts of our fingers; and, in this instance, oftentimes the hammer and anvil continue cold after the operation; which shews, that the heat acquired by the iron was not communicated by either of those implements as heat; but produced in it by a motion great enough strongly to agitate the parts of so small body as the piece of iron, without being able to have an effect upon so much greater masses of metal as the hammer or anvil. Though, if the percussions were often and briskly renewed, and the hammer were small, this also might be heated. Whence it is not necessary that a body should itself be hot to give heat.
"If a large nail is driven by a hammer into a plank of wood, it will receive several strokes on its head ere it grow hot; but when it is once driven to the head, a few strokes suffice to give it a considerable heat: for while, at every blow of the hammer, the nail enters further into the wood, the motion produced is chiefly progressive, and is of the whole nail tending one way; but when that motion ceases, the impulse given by the stroke, being unable to drive it further on, or break it, must be spent in making a various, vehement, and intestine commotion of the parts among themselves, wherein the nature of heat consists."
Sir Isaac Newton conjectures, that the sun and stars are only great earths vehemently heated: for large bodies, he observes, "preserve their heat the longest, their parts heating one another; and why may not great, dense, and fixed bodies, when heated beyond a certain degree, emit light so copiously, as by the emission and reaction thereof, and the reflections and refractions of the rays within the pores, to grow continually hotter, till they arrive at such a period of heat as is that of the sun? Their parts may be further preserved from fuming away, not only by their fixity, but by the vast weight and density of the atmosphere incumbent on them, strongly compressing them, and condensing the vapours and exhalations arising from them. Thus we see, that warm water, in an exhausted receiver, shall boil as vehemently as the hottest water open to the air; the weight of the incumbent atmosphere, in this latter case, keeping down the vapours, and hindering the ebullition, till it has received its utmost degree of heat. So also a mixture of tin and lead, put on a red-hot iron in vacuo, emits a fume and flame; but the same mixture in the open air, by reason of the incumbent atmosphere, does not emit the least sensible flame."
Agreeable to this, Sir Isaac is of opinion, that "gross bodies may be converted into light, by the
agitation of their particles; and light, again, into gross bodies, by being fixed therein?" and he defines fire to be "a body heated so hot, as to emit light copiously; for what, (says he,) is a red-hot iron, but fire?"
By others, fire is considered as a fluid sui generis, an original element, which "exists in all bodies, and may be separated or procured from them by rubbing them against each other, and thus putting their fire in motion. But this motion by no means generates the fire." This is the account given by Dr. Gravefande; with whom Lemery agrees, and endeavours to prove, that it is equally diffused through all space, is present in all places, in the void spaces between bodies, as well as the insensible interstices between their parts: of which opinion also was Dr. Boerhaave.
The first hypothesis having been adopted by such an eminent philosopher as Sir Isaac Newton, hath from thence received very considerable weight, and been generally received by the philosophers in this country. It is, nevertheless, pressed with almost insurmountable difficulties. It can by no means be explained upon the principles of mechanism, because it directly contradicts them.—It is certain, that if one body gives motion to another that resists it, the quantity of motion produced will be less than that of the first body; because as much will be taken off as the resistance of the first body was equal to. Thus, suppose a body moves in such a manner as to be able to raise 12 pounds; if it meets with an obstacle equivalent to six pounds, it will not, after driving it out of the way, be able to raise any more than six pounds. The same rule must hold equally, whether we suppose the parts of matter in motion to be large or small. In the above example, if we take ounces instead of pounds, we cannot suppose that the effect will be in the least disproportionate. If instead of ounces we take grains, or half grains, or the minutest particles, the effect must still be the same. Let us now take Mr. Boyle's example of iron becoming red-hot by being hammered. The momentum or quantity of motion impressed on the iron, by the blows it receives from the hammer, cannot be very great; we shall suppose them all together to amount to 500 pound weight. The momentum of the small particles of fire so produced, must be something less than 500 pound, on account of the resistance of them to motion. If these particles so put in motion, are employed to put in motion the particles of other matter, the momentum of these must be still less than that of the iron, on account of the new resistance met with. Thus, on every accession of new fuel, the fire must decay, and at last be quite extinguished. For, let us suppose the quantity of motion originally communicated to be great or small: if one part of matter gives motion to another, and that to a third, and so on, there is a constant loss of motion, occasioned by the resistance of the parts to be moved; and let us suppose this resistance as small as we please, as long as it is a resistance, an increase of the fire must be impossible. The contrary to all this, however, is confirmed by daily experience; and there seems to be no limit to the increase of fire, but the want of fuel. We cannot therefore mechanically account for the origin of fire merely on those principles by which we account for the motions of gravitating bodies.
To obviate in some measure objections of this kind,
Sir Isaac Newton seems to have supposed, that every particle of matter is endowed with a sphere of attraction, and beyond that with a sphere of repulsion. Hence, as soon as two particles of matter get without the sphere of one another's attraction, they begin to repel each other very strongly: and hence, says he, "as in algebra, where affirmative quantities cease, negative ones begin; so in mechanics, where attraction ceases, there the repelling power must succeed."
Upon this principle of repulsion alone it is that the mechanical origin of heat is tenible: for if the minute particles of any body have a force impressed upon them, in such a manner as to put them without the sphere of each other's attraction, and then they begin to repel one another strongly, it may be supposed, that putting the parts of other matter in a similar situation, and these again acting upon others in a like manner, a large mass of matter might be resolved into its minutest particles, and these scattered to an immense distance by the mutual repelling power between them, and thus produce the phenomena of heat and light.
Even this will be found quite unsatisfactory, if attentively examined; for the repelling power with which these particles are supposed to be endowed, will have as great a tendency to drive them back upon the body from whence they came, as to drive them away from it. To help our conceptions in this matter, let us suppose, that the repulsive sphere round each of the minute particles is an inch in diameter. Let us also suppose, that this repulsive force is sufficiently great to throw the particle to the distance of 1000 miles, when it comes within the repulsive power of another. If, therefore, a particle is driven off from any hard substance, suppose iron, it will indeed drive another before it, which is already in the way, but will as certainly drive back upon the iron those which are shaken off from it afterwards: for reaction is always equal to action; and if we suppose a number of such particles extricated from the body, their mutual action and reaction being always equal, the motion among them must very soon cease.
Upon this principle, however, the Newtonians explain the emission of light from luminous bodies. "A ray of light (says Sir Isaac), as soon as it is cast off from the luminous body by the vibrating motion of its parts, and is got out of the sphere of its attraction, is propelled with an immense velocity."—Now, with all due submission to such a great name as that of Sir Isaac Newton, what he advances here is utterly impossible. All the parts of the sun have a mutual attraction towards one another, by which they are kept together; and it is impossible that a particle of matter can be both attracted and repelled at the same moment by one body.—It is indeed inconceivable, how the particles of matter can be endowed with two such contrary powers, and yet remain together in one mass: for though those which lie contiguous to one another may mutually attract, yet they must also repel, and be repelled by, those which lie at a greater distance; and, from such a mixture of contrary forces, it does not seem that any body could solidly cohere together.
In support of this hypothesis, we may however suppose, that the vibratory motion of the parts of the sun is so great, that the particles of light are thrown off by it an immense way beyond the orbit of Saturn. But granting this,
this, no sooner would they come within the sphere of one another's repulsion, than some of them would be thrown back with violence towards the sun; and, in their return, would meet with others, to which they would give a like direction; and in this they would be assisted by the attractive force of the sun himself, by which means the force with which the light was emitted, must at first be resisted, and at last entirely destroyed.
But, whatever might be the case with the sun, the vibratory force of whose parts we may suppose to be inconceivably great, it is impossible that upon this principle any fire could be kindled by man: for the vibratory motion induced among the particles of any body by him, could never be greater than the force originally applied; and thus must unavoidably decay, on account of the continual resistance met with in setting the particles of other matter in the like motion.
To these objections we may also add, that, upon this hypothesis, fire ought to burn best in vacuo; because there the pressure of the atmosphere is taken off, and there should be the less resistance to the vibrations of the small particles. We find, however, that fire, so far from burning best in vacuo, is immediately extinguished; and that a free circulation of air is absolutely necessary to preserve it.—Professor Hamilton, indeed, of the university of Dublin, endeavours to account for this, by saying, that air is necessary only to blow off the ashes, &c. which would prevent the continuance of the motion. But if there were no other occasion for air than this, fixed or phlogisticated air would answer the same purpose; and both of these are found to extinguish fire. See AIR.
The property, indeed, that air hath of supporting fire, has generally induced people to think that the true pabulum or fuel of fire is contained in the air.—Others are by no means inclined to admit this hypothesis; but no conclusive argument hath yet been brought against it. Indeed, in a case where the agents are so exceedingly subtle, it seems impossible to prove the negative in this question. We see, that fire will not burn without air; therefore air brings continually a new supply of matter which is converted into fire. Our senses here give us positive evidence. Those who take the other side of the question, ought to bring a proof equally strong against this. Dr Hamilton, indeed, supposes fire to be otherwise sufficiently provided with pabulum; and, therefore, that air acts upon fire otherwise than by supplying it with fuel, as we have already hinted.
"Air (says he) is not less necessary for the support of fire than of animal-life; for fire will not long continue to burn without a circulation of air. Now, I suppose, this happens, not from its adding any thing to the pabulum of fire, (for fire seems to be otherwise sufficiently provided with pabulum), but rather on this account. That the air immediately about a body on fire is heated, and made specifically lighter than the air at some distance from it. This hot air, therefore, must ascend, and carry with it all those minute particles of different kinds which are thrown off from the burning body, and which would otherwise rest upon its surface, and thereby clog and stop the subtle vibrations of the burning matter, in which the nature of fire partly con-
sists. If, therefore, fire be confined in a close place, where there can be no circulation of air, the air about it, being soon saturated with the particles arising from the burning matter, will not be able to take up any more of them; and therefore the fire must go out, smothered, as it were, with such particles as are no longer combustible. Hence it is that fire burns faster when air is strongly blown upon it: for then the ashes are carried off as fast as they are formed on the surface of the burning body; and thereby the particles that have just taken fire, are kept quite free from every thing that can impede or clog their vibratory motion. The air in this case also will spread the fire quickly through the fuel, by blowing the particles that are already kindled, among those that are not; and perhaps the motion of the air in this case may promote the subtle vibrations in the burning matter by which the fire is propagated through its parts. As the air contains many subtle particles of the inflammable kind, it is not improbable, that these, mixing with the gross burning matter, may help to preserve and enliven the fire: but I think it most probable, that air supports fire chiefly by carrying off such particles as are burned out, and would therefore obstruct the progress of the fire; because we find, that the strong elastic steam of water driven violently out of the pipe of an æolipile, which will carry off those particles, will also blow up and increase the fire as well as air driven from the bellows, although the steam does not contain any inflammable particles."
Here we have no other reason given in support of this hypothesis, than that fire may be blown up by the steam issuing violently from an æolipile; but this reason is founded on a deception. This steam only blows up the fire by occasioning a violent motion in the air through which it passes; and thus forcibly drives it on the fuel, at the same time that it enters along with it; and thus is, in some measure, similar to the blowing up of a large fire by a stream of water, which is used in some places instead of bellows. Nevertheless, if the steam of the æolipile is only admitted to the fire, and the air totally excluded from it, the fire will be as effectually extinguished as if the stream of water employed to force the air into a large furnace was itself directed on the fuel.—Besides, on the Doctor's hypothesis, fixed, and many other kinds of air ought to be equally efficacious in preserving flame, as already observed; which are yet found to extinguish it as effectually, if not more so than water.
Among other hypotheses, it may not be amiss to mention the almost forgotten and exploded one published by Mr Hutchinson, and by him pretended to be plainly revealed in the sacred writings.—According to this gentleman, the nature of fire, of light, and air, are all at bottom the same, being only three different modifications of the same fluid. When air is blown upon a fire, then the grosser fluid is immediately reduced to its finest parts, and attains the utmost degree of possible fluidity, by the vehement attrition of its own particles, and those of the fire already kindled, against one another. Being continually pressed upon in this state by the surrounding gross air, it is sent out on all sides in streams of light, which being detained among the particles of the atmosphere, and having their motion stopped, become part of the air itself, and are again ready
Fire. ready to reassume their luminous and fiery appearance on proper occasions.
Setting aside the pretended authority of revelation, many people have been of opinion, that this hypothesis might be supported by very strong arguments drawn from matter of fact. The principal are the following.
10 Arguments in favour of this opinion
1. It is well known, that in all mixtures of different kinds of fluids, those which are rarest, and consequently less acted upon by the force of gravity than others, will rise to the top, and occupy the uppermost place in the mixture. Thus, if water and oil are mixed together, they will soon separate themselves, and the oil will swim at the top. This separation happens in consequence of their different degrees of density, by which the oil is less affected by the force of gravity than the water; not through any principle of innate levity, or any power of repulsion between this fluid and the bottom of the vessel. In like manner, when we see any other two fluids mixed, and one of them ascends, we ought not to conclude, that there is any unknown power of repulsion in that which ascends, more than in the other. If only one of the two fluids is visible, and that happens to be the ascending one, we ought not therefore to seek for the cause of its ascent in unknown and imaginary repulsions and vibrations, but rather to conclude that it is pressed upwards by the tendency of an invisible fluid of greater density downwards. In most cases this is allowed by all philosophers to hold good. The smoke of a fire, for instance, does not ascend from it, on account of any principle of positive levity, or on account of a repulsive power betwixt it and the fire from which it ascends, but from the greater tendency of the air downwards; in consequence of which, it is driven upwards with a force equivalent to the difference of their specific gravities. By analogy, (say they) we ought to apply this to the emission of light itself. We have no other proof of a repulsive power between the particles of this substance, than its constant ascent from a luminous body; and invent it in order to solve this phenomenon, when the same thing may be done with a much greater degree of probability, and more agreeable to the known laws of nature in other cases, by supposing the descent of a denser, though invisible, fluid towards that body.
2. It can be proved by experiment, that the matter of fire, or light, is convertible into a denser substance, subject to the laws of gravitation, and united to terrestrial bodies in such a manner as to become a part of their composition, while yet it is capable of being afterwards expelled by a renewal of heat, and of reappearing in the form of air.—The proof here rests upon the augmentation of weight observed in metals, when calcined either in the solar beams by means of a burning glass, or in a common fire. Thus, regulus of antimony, calcined in the focus of a large burning-glass, gains almost an eighth part of its whole weight; red lead, in calcination, gains a tenth part; and some of the other metals have been observed to gain much more. When these calces are suffered to cool, and are again exposed to the action of a strong fire, they discharge a large quantity of air. The fire, therefore, say the adopters of this hypothesis, has here been evidently converted into air; it being impossible that, during the continuance of a violent heat, any thing could be imbibed from the air; for the fire would so effectually
prevent any such absorption at first, as it could expel the air afterwards.
3. The phenomena of electricity show, that there is present between the grosser parts of bodies an invisible subtle fluid, of exceeding great power, which on certain occasions becomes visible, and then discovers itself to be the real element of fire itself. It always appears to our eyes as a stream of subtle fire, emitting a very perceptible light. It will kindle inflammable substances; melt the most difficultly fused metals, platina itself not excepted; and even turn gold into glass, which hath never yet been done either by the fiercest furnace or the strongest burning mirror.
Though this hypothesis has been laid down in its most distinct and plausible form by Hutchinson, or rather some of his followers, it appears very little if at all different from that of Boerhaave and others, who maintain the impossibility of generating fire, and affirm it to be a fluid sui generis. A direct proof of this, however, as well as of other suppositions concerning the nature of fire, is attended with great difficulties. Were we able to convert fire by itself into air, and convert air by itself into fire, the point would indeed be gained. But, though we blow ever so much air into a fire, unless we continually add new fuel, it will soon be extinguished. But this ought not to be the case on the Hutchinsonian hypothesis: for one quantity of air being reduced to its utmost degree of fluidity, ought to reduce to the same state every succeeding quantity which mixed itself with it; and not only would fire be kept up without any gross fuel, but there might be some danger of setting the whole atmosphere in a blaze at once.
Thus, while one party is at a loss to account for the usefulness of air in supporting fire, the other is no less distressed with the gross fuel, such as wood, coals, &c. which seem to be equally necessary with the air itself for the support of our fires. The Hutchinsonians, indeed, find no other use for the fuel but to keep off too great a quantity of air, which would oppress and extinguish a small fire: but this purpose might be equally well answered by pieces of brick or stone; yet these will effectually put out a fire. The use of the fuel, therefore, which is continually to be added to our common fires, cannot be explained on the Hutchinsonian hypothesis.
The discoveries of Dr Priestley, however, have put the matter beyond a doubt with respect to air. He hath made it apparent, that terrestrial substances are necessary ingredients in the composition of air much purer than what we breathe, and much more capable of sustaining flame; so that it is now an absurdity to talk of fire and air being convertible into one another.
The great proof on the Hutchinsonian side, and which they look upon as absolutely unanswerable, is the increase of weight in metalline calces when exposed to the action of a strong fire. This increase is found to be owing to air, as we have already mentioned: and though it should by no means be found either fit for respiration, or for the purposes of supporting flame; yet it will be sufficient for their purpose to prove, that the element of fire is capable of being converted into a gravitating substance; which, when disengaged, appears in the form of a permanently ela-
Fire. sic fluid, and thus becomes a certain species of air.— That it really doth so, however, is very dubious: for it is certain, that metals cannot be calcined without the free access of air; and therefore it cannot certainly be known whether the air in the calx comes from the fixation of the fire, or whether it is attracted from the surrounding atmosphere, especially if, as some aldehyde, the calx receives no increment in weight while kept hot.
M. la Voisier mentions some very fine experiments with regard to the calcination of metals, which ought to throw a considerable light on this subject.— Having put three drachms of lead in a stone crucible placed under a glass-receiver inverted in quicksilver, he exposed it to one of Tschirnhäusen's great burning-glasses; keeping it, however, a full inch from the true focus, that the heat might not be much greater than was necessary to melt the metal.
At the very instant the lead melted, though it was perfectly clean and bright on every side, a pellicle was produced on its surface. In the progress of the calcination, this pellicle became of a yellow massicot colour, and wrinkled on one side. In ten or twelve minutes the calcination stopped, and no farther effect was observed; only when the heat was a little stronger, the yellow pellicle fused in some places, and formed a yellowish glass. From the portions thus vitrified fumes arose plentifully, which tarnished the top of the cucurbit. This evaporation he opposed as much as possible, by removing the lead farther and farther from the true focus of the lens.
The metal having been exposed to the action of this lens for an hour and 15 minutes, and the vessels then perfectly cooled, it was found to have gained grains. The mercury was found to have gained lines above its former level. The diameter of the receiver in that place was inches, so that the whole quantity of air absorbed was cubic inches. The proportion of the increase of weight in the calx then, had been of a grain for each inch of air, which is about one fourth more than the weight of an equal quantity of atmospherical air. Having made some experiments on the air which remained in the receiver, he found that it would not precipitate lime-water, and thus seemed to be deprived of its fixed part.
To the same purpose Dr Priestley hath made experiments on metallic calcinations; and acquaints us, that if a metal is calcined over lime-water, it doth not become turbid; because, though the calcareous earth attracts the fixed air, yet the metallic calx doth it much more strongly, and consequently no precipitation can ensue. The same reason he gives why metals cannot be calcined in nitrous air; namely, that there is then no fixed air with which the metallic calx may combine, and upon which the calcination seemed to him to depend; nevertheless, the metals fumed copiously, though the phlogiston was not separated.
These experiments seem totally unanswerable by the Hutchinsontians. It is well known, that fixed air is one of the component parts of our atmosphere; and from M. la Voisier's and Dr Priestley's experiments, it would seem impossible to deprive a metal of its phlogiston, but by allowing the calx to combine with fixed air; and as the fire, though constantly applied, is not
able to produce this fixed air, but must have the assistance of the common atmosphere, this seems a demonstration, that fire is not convertible into an elastic fluid of any kind.
The only reply which the Hutchinsontians can give to this is, that metals will be increased in weight tho' kept over the fire in close vessels. But this may very reasonably be supposed to proceed from the small quantity of air contained in the vessels where they are put, or from some inaccuracy in closing them, so that there may be some communication between the metals and the external air. To make these experiments perfect, the glasses ought first to be well exhausted of their air, and then hermetically sealed.
It doth not appear, therefore, that ever the element of fire hath been by human art converted into a grosser fluid of any kind; and consequently the only resource left the Hutchinsontians is in arguments drawn from the similarity of the electric fluid and the substance of light or fire. The late discoveries in electricity, indeed, have thrown so much light upon that subject, that there are now but few who deny the existence of fire as a distinct element. It doth not, however, appear, that this element can ever be converted into any other fluid of a grosser nature, as the Hutchinsontians affirm. The electric fluid seems to be equally subtil, and equally penetrating, with fire or light; and though it should remain ever so long at rest, it doth not appear that its fluidity is thereby lost in the smallest degree. But for a full account of the experiments most likely to ascertain the identity of elementary and electric fire, see the articles ELECTRICITY, HEAT, IGNITION, LIGHT, &c.
Wild Fire, a kind of artificial or fictitious 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 raw hides.
Its motion or tendency is said to be contrary to that of natural fire, and always follows the direction in which it is thrown; whether it be downwards, sideways, or otherwise. The French call it Greek fire, or feu Grecois, because first used by the Greeks, about the year 660; as is observed by the Jesuit Petavius, on the authority of Nicetas, Theophanes, Cedrenus, &c.
The inventor, according to the same Jesuit, was an engineer of Heliopolis, in Syria, named Callinicus, who first applied it in the sea-fight commanded by Constantine Pogonates against the Saracens, near Cyzicus, in the Hellespont; and with such effect, that he burnt the whole fleet therewith, wherein were 30,000 men.
But others will have it of a much older date; and hold Marcus Gracchus the inventor: which opinion is supported by several passages, both in the Greek and Roman writers, which shew it to have been anciently used by both those nations in their wars. See Scaliger against Cardan.
Constantine's successors used it on divers occasions, with equal advantage as himself; and what is remarkable enough, is, that they were so happy as to keep the secret of the composition to themselves, so that no other nation knew it in the year 960.
Hugh, king of Burgundy, demanding ships of the emperor
Fire. emperor Leo, for the siege of Fresne, desired likewise the Greek fire. Chorier Hist. de Dauph.
F. Daniel gives us a good description of the Greek fire, in his account of the siege of Damietta under St Louis. Every body, says that author, was astonished with the Greek fire, which the Turks then prepared; and the secret whereof is now lost. They threw it out of a kind of mortar; and sometimes shot it with an odd sort of cross-bow, which was strongly bent by means of a handle, or winch, of much greater force than the mere arm. That thrown with the mortar, sometimes appeared in the air of the size of a tun, with a long tail, and a noise like that of thunder. The French by degrees got the secret of extinguishing it; in which they succeeded several times.
Ann. Reg. xviii. 117. Machine for Preserving from Fire. This machine, consists of a pole, a rope, and a basket. The pole is of fir, or a common scaffold pole, of any convenient length from 36 to 46 feet; the diameter at bottom, or greatest end, about five inches; and at the top, or smallest end, about three inches. At three feet from the top is a mortise through the pole, and a pulley fixed to it of nearly the same diameter with the pole in that part. The rope is about three quarters of an inch diameter, and twice the length of the pole, with a spring hook at one end, to pass through the ring in the handle of the basket when used: it is put through the mortise over the pulley, and then drawn tight on each side to near the bottom of the pole, and made fast there till wanted. The basket should be of strong wicker-work, three feet and a half long, two feet and a half wide, rounded off at the corners, and four feet deep, rounding every way at the bottom. To the top of the basket is fixed a strong iron curve or handle, with an eye or ring in the middle; and to one side of the basket, near the top, is fixed a small cord, or guide-rope, of about the length of the pole. When the pole is raised, and set against a house over the window from which any persons are to escape, the manner of using it is so plain and obvious, that it needs not be described. The most convenient distance from the house, for the foot of the pole to stand, where practicable, is about 12 or 14 feet. If two strong iron straps, about three feet long, rivetted to a bar cross, and spreading about 14 inches at the foot, were fixed at the bottom of the pole, this would prevent its turning round or slipping on the pavement. And if a strong iron hoop, or ferule, rivetted (or welded) to a semi-circular piece of iron spreading about 12 inches, and pointed at the ends, were fixed on at the top of the pole, it would prevent its sliding against the wall.
When these two last mentioned irons are fixed on, they give the pole all the steadiness of a ladder; and because it is not easy, except to persons who have been used to it, to raise and set upright a pole of 40 feet or more in length, it will be convenient to have two small poles, or spars, of about two inches diameter, fixed to the sides of the great pole at about two or three feet above the middle of it, by iron eyes rivetted to two plates, so as to turn every way; the lower end of these spars to reach within a foot of the bottom of the great pole, and to have ferules and short spikes to prevent sliding on the pavement, when used occasionally to support the great pole, like a tripod. There should be two strong ash trundles let through the pole, one at
four feet and one at five feet from the bottom, to stand out about eight inches on each side, and to serve as handles, or to twirl the rope round in lowering a very heavy weight. If a block and pulley were fixed at about the middle of the rope, above the other pulley, and the other part of the rope made to run double, it would diminish any weight in the basket nearly one half, and be very useful in drawing any person up, to the assistance of those in the chambers, or for removing any effects out of a chamber, which it might be dangerous to attempt by the stairs.
It has been proved, by repeated trials, that such a pole as we have been speaking of can be raised from the ground, and two or three persons taken out of the upper windows of an house and set down safely in the street, in the space of 35 seconds, or a little more than half a minute. Sick and infirm persons, women, children, and many others, who cannot make use of a ladder, may be safely and easily brought down from any of the windows of an house on fire by this machine, and, by putting a short pole through the handles of the basket, may be removed to any distance without being taken out of the basket. The pole must always have the rope ready fixed to it, and may be conveniently laid up upon two or three iron hooks under any shade or gate-way, and the basket should be kept at the watch-house. When the pole is laid up, the two spars should always be turned towards the head of it. The basket should be made of peeled rods, and the pole and spars painted of a light stone-colour, to render it more visible when used in the night.
Godfrey's Machines for Extinguishing Fire. Of these the following account is given by Mr Ambrose Godfrey, grandson to the inventor. "The machine to be employed, consists of a small portion of gun-powder closely confined; which, when animated by fire, acts by its elastic force, upon a proper medium, and not only divideth it into the minutest atoms, but dispereth it also in every direction, so as immediately to extinguish any fire within a certain distance. This medium is a liquor strongly impregnated with a preparation of antiphlogistic principles, which, by their action upon burning materials, extinguish the flames, and reduce them in general to a state of a black coal; and, by its opposite nature to fire, hinders the remaining sparks, notwithstanding the admission of the air, from kindling the flames afresh. By this means, the great point is obtained, in giving sufficient time for totally extinguishing any remains of fire.
"They who presume that water only will perform this, will find themselves greatly mistaken, as the draught of air will certainly rekindle the neighbouring materials, which are very fit to receive a fresh flame, the fire not being extinguished by the quantity of water, but rather by the expansion and rarefaction of its particles. There are several sizes of these machines, from five to fifty pounds weight, in a portable and rather small compass, and may generally be carried to any place where a man can go himself.
"But tho' these machines will prevent great fires by a timely application, they will not extinguish them after they have reached a frightful height, and several houses, perhaps near a whole street, are in flames. The floors must be standing, and access to the building safe, otherwise no person can be supposed to approach
Fire. near enough to apply them in a proper manner. Every fire has its beginning, for the most part, in some apartment; and as soon as discovered, the family, instead of losing all presence of mind, should immediately apply one or more of these machines, which will then fully answer the intention. The proper time of applying them, supposes that they are ready at hand. It will be in vain to think of fetching them from any considerable distance, as it will then be too late for them to perform any important service; except indeed being the probable means of saving some adjacent house, by extinguishing the flames as often as they break out, till the building first on fire is totally consumed, and, by falling into ruins, leaves the other in perfect safety."
On the 19th of May 1761, at noon, Mr Godfrey's experiment for extinguishing fire, was tried in an house erected for that purpose, near Mary-le-bone. Their royal highnesses the duke of York, prince William Henry, prince Henry Frederick, a great number of persons of rank and distinction, and many of the learned world, gave their attendance on this singular occasion. The house, which is of brick, consists of three rooms, one above another, a stair-case, chimney, lath-and-plaster ceilings, and a kind of wainscoting round the rooms, of rough deal. Exactly at 12 o'clock the ground-room, and that up one pair of stairs, were set on fire, by lighting the faggots and shavings laid in there for that purpose: in about 15 minutes the wainscoting of the under room was thought to be sufficiently in flames, and three of the machines were thrown in; which, by almost immediate and sudden explosions, instantaneously extinguished the flames, and the very smoke in that apartment in a few minutes totally disappeared. By this time, the firemen, &c. who had the care of throwing in the machines, gave an alarm that the stair-case had taken fire, and that it was necessary directly to go to work upon the next room; which was accordingly done, and with the same effect. The experiment, however, hitherto did not universally satisfy: in the last instance especially it was thought to be too hastily put in execution; and the populace, without side the paling, who were supposed to amount to near 20,000, and whose curiosity, from the very nature of their situation, remained much dissatisfied, began to grow rather riotous, and talked of a second bottle-conjuror. For the sake of the experiment, therefore, and to remove all manner of doubt, Mr Godfrey consented to a third experiment in the upper room, which was entirely of wood. The flames were now suffered to get to a considerable height, and even the window-frames destroyed, before the machines were thrown in; which, however, answered exactly as the former had done; and, being quite in sight of the out-landers, met with universal approbation.
In the year 1734, the states of Sweden offered a premium of 20,000 crowns for the best method of stopping the progress of accidental fires; when one Mr Fuches, a German physician, made a preparation for that end, and the experiment was made on a house built on purpose, of dry fir, at Legard island. In the buildings were placed several tubs of tar and pitch, and a great quantity of chips, all which were set on fire; flames issuing through the top of the house, windows, &c. when he threw in one of the barrels containing the preparation, which immediately quenched the flames;
a second barrel entirely cleared the smoke away; and the whole was executed to the satisfaction of the spectators, and to the no small satisfaction of the inventor, who was about to return home, when unexpectedly the flames broke out again, supposed to be occasioned by a small quantity of combustible matter being introduced and set on fire secretly by some malicious person. Upon this the wrong-headed mob fell upon Mr Fuches, and beat him most unmercifully, so that he narrowly escaped with his life. He soon after left the country, and never could be prevailed on (tho' strongly persuaded by some of the most eminent citizens) to return. It is said, another experiment of the same kind was tried in the year 1761 in Holland; but rendered abortive through the perverseness of the populace.
These machines of Mr Godfrey's, it is evident, would be of great use in extinguishing fires on shipboard; and might be considered as a no less necessary part of a ship's lading, than her stores or ammunition.
The hint of these machines is said to have been taken by Dr Godfrey from the invention of one Zachary Greyl, who exhibited machines similar to those of Dr Godfrey, before persons of the first rank, but without meeting with any encouragement. His machines were made of wood, and the liquor employed was only water, and consequently inferior to Dr Godfrey's in its power of extinguishing fire. The latter is said to have mixed his water with a certain quantity of oil of vitriol, or with sal ammoniac. These machines, however, are found to be only serviceable in the beginning of a fire. When the roof had fallen in, they had no effect.
Water-Engine for Extinguishing Fire. See HYDROSTATICS, uo 33.
In using this machine we have the following improvement by Dr Hoffman, which promises to be of great efficacy. As soon as the engine is in readiness to work, stir into the water that immediately is to be discharged, seven or eight pounds of pearl-ashes in powder, and continue to add it in this manner as occasion requires; taking care that it be directed against the timber or wainscoting, &c. just beginning to burn, and not wasted against the brickwork: or, where time will admit, dissolve any quantity of pearl-ashes in a copper with water, and as fast as it dissolves, which will be in a few minutes, mix a pailful with the water in the engine, pretty often; and whatever burning wood it is played upon, will be extinguished as if it was dipped in water, and will not burn afresh in the part extinguished.
Use of Gun-powder for Extinguishing Fires. It is well known, that the inner parts of chimneys easily take fire; the foot that kindles therein emits a greater flame, according as the tunnel is more elevated, because the inferior air feeds the fire. If this air could therefore be suppressed, the fire would soon be extinguished. In order to this, some discharge a pistol into the chimney, which produces no effect: others lay under the chimney a copper full of water; but the vapours that rise from it, far from extinguishing the fire, seem to give it new force. Water thrown into the chimney at top is equally of no effect, because it comes down through the middle of the tunnel, and not along the sides. It would be more advisable to stop with dung the upper orifices of the tunnel for quenching
Fire. ing the fire. But the surest and readiest method is, to take a little gunpowder, and, having humectated it with spittle for binding it, to form it into small masses, and to throw it into the hearth of the chimney. When it is burnt, and has produced a considerable vapour, a second, afterwards a third, are thrown, and so on, as much as is necessary. In a little time the fire is extinguished, and, as it were, choked by this vapour; and cakes of inflamed foot are seen to fall from the tunnel, till at last not the least vestige of fire appears.