Fires.

As regards the cause of conflagrations, division of the subject is simple: fire may either break out because of the application of fire, or as the result of spontaneous combustion; and when once originated, the devastation and spread of fire will be merely determinable by the circumstances,―viz. the nature of materials ignited, and the construction of the premises as to draught. Taking an ordinary dwelling-house as supplying the first and simplest case for illustration, let us look around at the materials of which it is composed, and speculate on the functions of each. Here be it noted, that the reader who has not given study to the process of combustion will have to modify several of his most fixed ideas, if indeed he be not called upon to give credit to statements absolutely opposed to his common belief. A modern dwelling-house-let us take stock of the materials which compose it; separating the combustible from the incombustible if we can, at any rate discriminating between varying degrees of combustibility. Wood, iron, bricks, stone, plaster,-these are the chief materials of which houses are built; to the above list lead may usually be added, and perhaps zinc. The question now being proposed, "Which material is the most combustible of the lot?"-" Wood," almost every body unhesitatingly replies. That depends on circumstances, however; and here, par parenthèse, may the fact be noted, that water (the grand antagonist to combustion, as it is popularly considered) not only fails to check conflagration under certain circumstances, but performs itself the function of a combustible. Unquestionably if, without limiting conditions, a chemist were asked whether iron and lead on the one part, and wood on the other part, were the more prone to burn, he would award the palm to iron and lead; seeing that either of these metals, if reduced to impalpable powder by chemical means, will take fire spontaneously; whereas no possible degree of attenuation can bring woody matter into the same category. The conditions under which iron and lead become spontaneously combustible are never fulfilled in the ordinary routine of building; but the intrinsic fact is advantageously borne in mind, nevertheless, seeing that the remembrance of it will dissipate a very common fallacy. No one substance in nature is absolutely incombustible. To the function of combustion, either as a combustible or supporter of combustion, every particle of nature's matter is bound to minister, by the very tenure of existence.

The mind is prone to associate the idea of combustibility alone with the materials commonly employed by us for fuel and illumination. Thus, according to the logic of common sense, a candle is combustible by the very evidence of its burning; whereas the candlestick is non-combustible by the very evidence of its not burning when the candle material is consumed and the candle-flame reaches the socket. The argument must

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necessarily be inconclusive, merely going to show that at one particular maximum of heat a candle ignites, whereas a candlestick does not. is very important; for whereas the point may be conceded that (ordinary dwelling-houses being in question-edifices where materials of no extraordinary danger are stored) iron, lead, zinc-metals in the aggregate, to generalise-are all fire-proof, yet when bonded warehouses, with all their heterogeneous materials are concerned, no such conclusion is valid. Whether iron and other metals shall be deemed practically combustible or not, will altogether depend upon the energies capable of being brought into operation. Such is the doctrine of the chemist. And here, in pure justice to poor Braidwood, the admission must be made that he, years ago, arrived at the same conclusion. There are no certain means of discovering and noting very high temperatures: wherefore to indicate one known and fixed temperature at which iron begins to burn is pure speculation-no better: when it does commence burning, however, it burns with a vengeance; and whereas wood when burning evolves flames, a form of combustion that admits of being controlled by water, iron rolls forth an uncontrollable lava-stream of far-reaching desolation.

Scanning the contributions of poor Braidwood to the "Transactions of the Civil Engineers,"-studying also the little tract which first brought him into notice, it will be perceived that he strenuously aimed at drawing a marked distinction between ordinary conflagrations and the graver case of fire run wild, as we recently saw evidenced.

Practically, in dwelling-houses, iron is incombustible; yet, contradictory though it should seem, an apartment may be incombustible and still not fire-proof. That is to say, its walls may grow incandescent, thus tending to propagate fire to whatever combustible matter may chance to be in contact with them on the outer side. The profuse employment of iron for building purposes--public, private, or technical-is attended with grave dangers other than combustive. Of all solid bodies, metals expand most when heated; and the force of expansion is indomitable: easier far to restrain the escape of the gases evolved from inflamed gunpowder, than to restrain the expansion of an iron bar under the influence of heat.

Contemplating the labyrinth of iron-bar work to be seen in numerous buildings, one can readily form a notion of the terrific thrusts iron pillars and beams would exert if once brought within the influence of a severe conflagration. No one contingency of a fire is so much dreaded by fireengineers as this. Strictly speaking, no edifice absolutely fire-proof,-in other words, wholly incombustible,-has been, or ever can be, built. Even the pyramids of Egypt could be consumed on the ground whereon they stand, if, for some sufficient reason, it should seem fitting to the ruler who watches over them to set philosophers the task. Nevertheless bricks and stone are within the ordinary limits imposed on the term incombustible; and, what is of no less importance, both are composed of materials which expand but slightly under the influence of heat.

Dwelling-houses considered, perhaps more protectiveness may be sought

in improved planning and disposition of parts than in mere incombustibility of material. Fire once broken out, the great aim should be to cut off the supply of supporting air, without which no fire can long maintain itself; to prevent draught, that is to say. Supposing fire to have broken out in some particular room, doors and windows should at once be shut, if possible. Wood-indeed every ordinary combustible-yields a gas as the result of its combustion, in an atmosphere of which gas combustion is no longer possible. If, however, a current of fresh atmospheric air be admitted, and the gaseous products of combustion driven away, then do we have the exact condition of a chimney. Apropos of chimneys, the announcement may as well be made at once, that although chimneys are answerable for many house conflagrations, staircases are answerable for more. A chimney on fire is no very serious matter if it be a well-built chimney; if the ends of joists and beams,—if woodwork of every sort and condition, be absent; but when once flame has welled out into the staircase of an apartment, the culminating point of danger has been achieved. Functionally, the staircase of a house, when flame has reached it, may be regarded as a chimney,—a chimney, too, in the construction of which almost every possible condition of safety has been violated.

A chimney on fire is no very serious matter, provided the chimney be unexceptionably constructed. At the time being, however, no one of those most concerned is very likely to have, or to be able to acquire, sufficient information upon that point; wherefore I would counsel that a chimney on fire, whether well or ill constructed, should be treated with consideration. What, then, should be done? If possible (but it rarely is possible) the very best thing to do would be to get upon the roof with a flat tile or iron plate in hand, and lay it coverwise across the chimneytop. This treatment not being possible,-none being possible at the upper end of the chimney,-let us see what, with propriety, can be done at the lower end. If a fire-arm, gun or pistol, be in the way, to discharge it up the chimney is excellent. Heaps of burning soot will certainly fall, probably dislodging the fire from its seat wholly. The soot down and glowing, or a fire from ordinary fuel remaining on the hearth, a handful of brimstone should be thrown upon it, if possible; and finally a carpet or hearthrug, or a blanket dripping with water, should be promptly nailed before the chimney, with the intent of obviating all further draught. The sulphur treatment is very good practice. Burning, it yields sulphurous acid gas, in an atmosphere of which nothing can burn.

If a chimney or chimney-place be not the fire-focus, if a conflagration have broken out elsewhere in an apartment, then also it is very proper (if possible) to hang a wet blanket in front of the fireplace as before. By proceeding thus, draught will be prevented.

Whilst a fire can be prevented extending to a staircase, a house need not be despaired of; but once the flame tongues playing there, safety of property is next to hopeless. Other circumstances being equal, the dan