The following extracts are from the experiments and conclusions of Rumford, with supplements by Prof. Mattieu Williams, of England. (See "Knowledge," Nos. 171 to 205, "Philosophy of Clothing.")
The physiological confirmation of these results are not quoted; confining the citations to the qualitative value of fibres, especially sheep's wool, and the possibility of materials therefrom that possess the essentials recommended.
The first use of clothing being to keep the wearer warm, Rumford's first inquiry was directed to find the best material for this purpose. He saw at once that clothing did this by resisting the passage outwards of the animal heat.
He accordingly constructed a model wearer, as described in the following experiments: A mercurial thermometer, whose bulb was 55/100th of an inch in diameter, and its tube about ten inches long. This was suspended in the axis of a cylindrical glass tube about three-quarters of an inch in diameter, ending with a globe 1 6/10 inch in diameter, in such a manner that the center of the thermometer bulb occupied the center of the globe, thus leaving a surrounding space to be occupied by the material to be examined. The thermometer tube was graduated with 800 divisions between the freezing and boiling points of water—i. e., a Reaumur scale divided to tenths of degrees. The thermometer was held in its place by a long cork stopper.
He described his method of clothing the bulb as follows: The thermometer being taken out of the cylindrical tube, about two-thirds of the substance which as to be the subject of the experiment is introduced into the globe; after which the bulb of the thermometer introduced a few inches into the cylinder; and after it, the remainder of the substance being placed round about the tube of the thermometer: and lastly, the thermometer being introduced further into the tube, and being brought into its proper place, that part of the substance which, being introduced last, remains in the cylindrical tube above the bulb of the thermometer, is pushed down into the globe, and placed equally round the bulb of the thermometer by means of a brass wire, which is passed through holes made for that purpose in the stopple closing the end of the cylindrical tube.
The temperature he selected as the starting point was 70 degrees Reaumur=190 degrees Fahr. He preferred this to the boiling point, as he could obtain it accurately by first plunging the whole apparatus duly charged into nearly boiling water, then allowing it to fall to 70 degrees, and immediately plunging it into a mixture of pounded ice and water, where, by the aid of a little agitation, it remained steadily at the freezing point.
The following table shows the results with the substances therein mentioned, the quantity in each case being 16 grains:
| HEAT LOST. | RAW SILK AS SPUN BY THE WORM. | SHEEP'S WOOL. | COTTON WOOL. |
|---|---|---|---|
| 70° | .... | .... | .... |
| 60 | 94" | 79" | 83" |
| 50 | 110 | 95 | 95 |
| 40 | 133 | 118 | 117 |
| 30 | 185 | 162 | 152 |
| 20 | 273 | 238 | 221 |
| 10 | 489 | 426 | 378 |
| Total times | 1,284 | 1,118 | 1,046 |