The advantages which may be derived from candles that require no snuffing and afford no smoke, may be readily understood; but these candles have another property which ought not to be passed over in silence. A candle snuffed by an instrument gives a very fluctuating light, which, in viewing near objects is highly injurious to the eye; and this is an inconvenience which no shade can remove. But when a candle is snuffed spontaneously, it gives a light so perfectly steady and so uniformly bright, that the adjustments of the eye remain at rest, and distinct vision is performed without pain, and without uneasiness. Candles, on which Mr. WALKER has made experiments, are described in the following TABLE. +-----+--------------+---------+---------------+ | |No. of candles| | No. of single | | No. | to the pound |Length in|threads of fine| | | avoirdupoise | inches. | cotton in the | | | weight. | | 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.