WHAT IS FIRE PROOF?

Colonist, Volume IV, Issue 425, 19 November 1861, Page 3

WHAT IS FIRE PROOF?

• Fireproof !' echoes the casual thinker, • nothing more easy than to determine what is and what is noc a fireproof building. Fireproof means anything that will not burn; construct a dwelling-house or warehouse of iron, for example, and it will be fireproof—incombustible.' This has long been a common notion ; and architects have somewhat too complacently given way to it; |but no person, technical or untechnical, having eyes in his head and sense to correspond, could have looked upon the devastating ravages of the fire on the wharves last week without utterly abandoning the notion that iron is incombustible. The fact is that, gire a degree of heat high enough, iron is remarkably combustible. A fine needle plunged into the flame of a burning candle, for example, scintillates and consumes. As the candle flame may increase in power so may the experimental needle increase in size; sufficient indication of what may be expected to take place on the exposure of pillars, braces, or girders of iron to the tremendous flame of a warehouse holding highly combustible materials. Under the latter condition masses of iron, wrought as well as cast, fuse readily, and, a sufficient draught of air being supplied, burn. Quite fallacious, then, is it to count upon the fireproof functions of mere iron. Nor is this all that admits of being said to the disparagement of iron, used as a building material, when exposed to violent heat. Long before the fusing point is arrived at other dangers are imminent, Every degree of heat imparted corresponds with an amount of strength removed, so that when the temperature has been raised to about 600 degrees Fahrenheit, to about the fusing point of lead, that is to say, the cohesive strength of iron, wrought and cast, is diminished probably one-third. Again, an inevitable effect of heat on metal is to promote expansion, and inasmuch as expansion — iron pillars, braces, and girders being in question:—means elongation, a sufficient explanation is afforded of the thrusting apart and demolition of walls iron-braced and iron-supported, so soon as fire has fairly begun to rage in the building.

It is curious, and at the same time very melancholy, to consult the recoids of the Association of Civil Engineers for 1849, and therein peruse she subject matter of a paper read by the lamented Braidwood, embodying the above-mentioned views. So pointedly do his remark? bear upon the conditions and results of the g eat fire, that the mind almost refuses to believe that it was not written after the event. Had the spirit of prophecy been vouchsafed to poor Braidwood he could not more clearly have p:edicted what some day would happen, tha,n

what indeed has happened, himself being the victim. Nor, in our opinion, did the lamented engineer make so much of \m case as is possible and legitimate. In pointing out the fusibility of iron under strong heat s the weakening of it as to cohesion, and the violent thrust against roofs and walls owing to metallic expansion, he failed to take cognisance of the fact that whenever a jet of water is spouted against a surface of iron sufficiently hot, the water is, so to speak, turned into a violent combustible; or, scientifically speaking, oxyde of iron being formed, hydrogen is devolved under the condition of a most inflammable gas. Persistently throughout his life, or at any rate throughout that portion of his life which had been devoted to the fireman's avocation, Mr. Braidwood never ceased to protest against the practice of using iron profusely in architectural structures, under the impression that the latter were thereby rendered fireproof; and he very solemnly predicted that under the prevalence of the system in question fires were in store, by comparison with which all fires for many a long year past would be but as playthings. To the last poor Braidwood protested that bricks, mortar, and wood were materials far more fireproof in a practical sense than iron; but inasmuch as bricks even can be consumed, given heat enough, evidently the designation of' fireproof' is only one of degree: a statement the truth of which being fully recognised, it becomes all the more incumbent on the owners and inhabitants of buildings, warehouse buildings especially, to provide against the ravages of fire by a more strict internal arrangement and general economy than might be deemed necessary were the point once established that there could be any absolute realisation of the term ' fireproof.'— Morning Post.