CAST IRON PILLARS IN THE EVENT OF FIRE.

New Zealand Herald, Volume XVI, Issue 5583, 7 October 1879, Page 6

CAST IRON PILLARS IN THE EVENT OF FIRE.

TO THE EDITOR. Sir,—At the last meeting of the City Oouucil, a strongly-worded report was read from Mr. Hughes, superintendent- of the Fire Brigade, in reference to cast iron columns used in a building in Shart'.aud-atreet. Tho subjoined extract, cut out of he Scientific American supplement, will be found pertinent, as the matter is really of importance. —I am, &e., G.A. Fireproof Pillars.—The plan which we gave in the lieview for June, of a safe pillar for architectural purposes—an interior solid core of wood and an outer thick shell of cast iron—has brought us several communications from manufacturers of composite " fireproof " pillars. In each case of these the centre is a hollow circular iron core, with divergent ilauges—tha spaces between the latter being in oue instance filled witb oak wood bound with band-i, and in others with fireproof blocks of clay or cement, duly clamped on with iron bands ; and such posts are generally intended to be finished by plastering. We are glad to see these evidences of attention to an important subject, especially as one comes from Chicago, where such attention is much needed. We wish the manufacturers success, but think they have not commenced at the right point in their protective efforts. They seem to forget that tho iron hoop clamps may burn off, and that any way the heat, always above ISO* I'\, must reach the interior pillar ,* then there will be expansion, throwing off the covering, or if not, the heat—without actual contact of ilamc—must weaken greatly the iron, and all the weight being upon it, the probability is it would bend and break. We still hold that an interior tolid wooden post, with an exterior cast iron shell of one inch thickness, would be safer than any of the composite patent pillars exhibited to us. The groat danger in a fire is, that intense heat—we will not say flame—would reach the iron through even fireproof clay, for every one has seen that material red hot in cylinders of stoves; then, according to our views, as expressed in another article iu this lievtew, intense molecular vibrations must ensue, which would weaken the iron, and tho superincumbent weight of three, four, or more stories would aid to bear down the pillar. In the pillar we suggested, the iron resisting fire would be supported against the weakness of its cohesion for a much longer time than if it were not assisted by the interior solid post of wood; and although the iron become red hot, it would still shield the wood from the fierce Came. The outer pillar, if red-hot, could but char the exi.erior of the wooden post, for there would uo3 be air enough to support llame between the iron and wood. Meantime, in such a fire tno outer iron pillar being red-hot, and confessedly useless to bear greit weight, the wooden post lias assumed all the burden and

upheld all the weight, which is what =■ claim it will do in any ordinary fire Vh outer iron shell being thus relieved frn pressure, remains in its place as a ahieM from flame, although it may become as in.f stated, red-hot, or even up to a while hi-I* The principle of no space left for air between the wooden post and the iron shell is ano f we strongly insist upoa in suggesting this form of pillar. As an evidence of how he will penetrate terra-cotta ware, we will tne tion that a fire took place in a laundry Marble-street, above Tenth, Philadelphia July 14, where the shingle roof was set on fire and some damage done through a stove pipe surrounded by a terra cotta pip» which ran close underneath the bare rafters and shingles. The difference between •< (ireproofing" a wooden and an iron support i» this. Wood is strong against heat un to flammabihty; iron is weak against beit but is fusible only at very high temperature' and not flammable, or very slightly 8 0. The covering of the iron column admits tho heat to tho iron; the iron covering the wood largely keeps tho wood from flaming.— Anterican Ex. and lieview.