Candles, on which Mr. Walker has made experiments, are described in the following
TABLE.
| No. | No. of candles to the pound avoir- dupoise weight. | Length in inches. | No. of single threads of fine cotton in the wick. | |
|---|---|---|---|---|
| 1 | 14 | 8. | 5 | 10 |
| 2 | 13 | 9. | 12 | |
| 3 | 10 | 9. | 74 | 14 |
| 4 | 8 | 10. | 20 | |
| 5 | 6 | 10. | 25 | 24 |
| Mould | 6 | 13. | ||
Number 1, 2, and 3. These candles, when lighted and placed to form an angle of 30° with the perpendicular, require no snuffing: they give lights which are nearly equal, and combustion proceeds so regularly, that no part of the melted tallow escapes unconsumed, except from accidental causes.
No. 4, placed at the angle mentioned above, and lighted, requires no snuffing: it gives a light very little stronger than No. 1, but its colour is not quite so white, nor its flame so steady.
No. 5. This candle, placed at an angle of 30°, and lighted, requires no snuffing; its flame is rather fluctuating, and not so white as No. 4, nor is its strength of light much greater than No. 1. The melted tallow sometimes overflows when the air in the room is put in motion; yet the light of this candle is much improved by being placed in an inclined position.
The mould candle, treated in the same manner, affords a very pure steady flame, without smoke and without snuffing, and its strength of light is about equal to that of No. 1.
The experiments have not been sufficiently numerous to determine with precision which of these candles affords the most light at a given expence, but the few experiments which have been made seem to indicate, that the quantity of light is nearly as the quantity of combustible matter consumed, and thus a candle which is used in the manner pointed out gives more light than a candle of the same dimension set perpendicularly and snuffed, because one part of a candle that is snuffed, is thrown away, and another part flies off in the form of smoke. And this is not the only inconvenience that attends the using candles in this manner, and which the other method is free from, for the light which it gives is of a bad quality, on account of its being variable and undulating.
From the time that a candle is snuffed till it wants snuffing again, its strength of light scarcely continues the same for a single minute. And that variation which frequently takes place in the height of the flame, is a matter of still more serious consequence.
The flame of a long candle placed vertically when it is snuffed burns steadily, is about two inches high, but it very frequently rises to the height of four inches or upwards; drops down again in a moment, till it is less than three inches, and then rises again. In this manner the flame continues in motion for some time before it returns to its original dimensions. But it does not continue long in a quiescent state before it begins a new series of undulations. In this manner the candle burns till the top of the wick is seen near the apex of the flame, carrying off clouds of smoke. In this state of things the eye becomes uneasy for want of light, and the snuffers are applied to remove the inconvenience.