Sir H, Davy’s researches on flame. ' 71 
brought over the flame. Though at such a distance, it will 
instantly extinguish the flame, if it be cold: but if it be held 
above the flame, so as to be slightly heated, the flame may be 
passed through it without being extinguished. That the effect 
depends entirely upon the power of the metal to abstract the 
heat of flame, is shown by bringing a glass capillary ring of 
the same diameter and size over the flame; this being a much 
worse conductor of heat, will not extinguish it even when cold. 
If its size however be made greater, and its circumference 
smaller, it will act like the metallic wire, and require to be 
heated to prevent it from extinguishing the flame.* 
Suppose a flame divided by the wire-gauze into smaller 
flames, each flame must be extinguished in passing its aper- 
ture till that aperture has attained a temperature sufficient to 
produce the permanent combustion of the explosive mixture. 
A flame of sulphur may be made much smaller than that 
of hydrogene, that of hydrogene smaller than that of a wick 
fed with oil, and that of a wick fed with oil smaller than that 
of carburetted hydrogene; and a ring of cool wire which 
instantly extinguishes the flame of carburetted hydrogene, 
only slightly diminishes the size of a flame of sulphur of the 
same dimensions. 
Where rapid currents of explosive mixtures are made to 
act upon wire-gauze, it is of course much more rapidly 
heated ; and therefore the same mesh which arrests the flames 
* Let a small globe of metal of ^ °f an inch in diameter made by fusing the end 
of a wire be brought near a flame of ^ in diameter, it will extinguish it when cold at 
the distance of its own diameter; let it be heated, and the distance will diminish et 
which it produces the extinction ; and at a white heat it does not extinguish it by 
actual contact, though at a dull red heat it immediately produces the effect. 
