PUMICE INSULATION.

Otago Daily Times, Issue 10240, 24 December 1894, Page 7

PUMICE INSULATION.

TSST OF FIRTH'S PRIiTARED PUMICE.

HEPORT BY COLONEL FOX.

Tha following report upon the test recently made by Colonel Fox with Virth's prepared ; pumice hss bsen forwarded to tha Hon. K. J. Seddon, Defence Minister :—■ Sir, —In compliance with your instructions re thy above, I have the honour to report that this day I was present while an experiment was being carried on to test the insulating power of the pumice. The patentee, Mr J. O. Firfcb, of Auckland, had prepared a four-foot cube iron tank of gtb, inch thickness of iron, with a equaro surface of about 3t't taken out of the centra of the top. The tank was supported by bricks at esch corner, being thus raised abaut lfc from tbe ground. 'She pumice preparation was i poured into the tank, filling it to lfc from the bottom. On this was placed a 22m cubic iron box l-16th iucu thick. Into the box were put (1) a recording thermometer registering SBdeg I', (2) a deed on parchment bearing a red wax seal, (3) two one pound bank notes, and (4) a small quantity of gunpowder wrapped in broi»n paper. A cover of iron similar to that ot the sides was then placed ou the box and pumice was poured into tha tank until it was full, a thermometer bsing placed half-way in tbe pumice between a side of the tank and a side of the box. A piece of thin iron was then placed over the hole on the top of tho tank and was weighed down, A coaJ and wood fire was then lightad at 11.30 a.m. For the first half-hour a strong firo was maintained, but for the next half-hour this slacked oif, owing to want of proper wood. On this beiog obtained the fire was strengthened, and was maintained from 1 to 3 p.m. at intense heat. There was jusc sufficient breeze to make j the wood burn furiously, aud so large and hot! was the fire that it was with great difficulty that four men were enabled to stoke it. At 3 p.m. the tank had bulged so much that it became advisable to reduce tho fire, which was then allowed to burn down, and at 4- p.m it was raked away from tho taok and eventually extinguished by water from a hose. The fcauk j was then immediate!}' uncovered. Tha fcem- j peratnre in the puinica about 6in from the top , of the tank was found to be 210deg F. The temperature recorded by the thermometer which had been in the pumice during tho experiment was found to be 175deg F. The temperature of the pumice in close proximity to the box was 95deg F. The temperature of the thermometer inaide the box was recorded at 86deg F., aud of course the articles placed in the box were found iv thsir normal condition. The pumice had settled down 6in in ths tank, owing to the bulging of the oides, and tans on top of the inner box there was only about Bin of pumice covering the box at the end of tha experiment. Tha result of this was that the top of"the box was very warm, while the sides and bottom of the box wore quite cool. As this agreed with the record of the thermometers usyd in testing th« heat of tbe pumice at different distances from the sides of the. tank, I came to the couclusiou that under the couditions of the test a thickness oV Biu reduced the temperature from almoßt white heat to 175deg F., and a thickness of 12iu reduced the tsuipernture to 95deg F. The tank W3JS warmed up tor one and a-half hours, was then kept for two hours at intense heat, aud wpvs losing heiit for one and a-qnarter hours before it could bs approached. When it was opened itnvas practically only just below a state of rod heat. " I am of opinion that the pumice preparation used fully fulfilled its part. It appaara to bu praotically indestructible by heat, 'and possesses very wonderful insulating power.—l am, &c, " Francis J. Fox, Colonel. "Auckland, December 1,1894."