Proceedings of the Royal Society of London/Volume 2/Farther Experiments on the Combustion of explosive Mixtures confined by Wire-gauze with some Observations on Flame
In these experiments, the author examines what magnitude of wire and of apertures in the metallic gauze of his lamp is consistent with security against explosion of mixtures externally.
When the gauze is made of wire one fiftieth of an inch in diameter, and at intervals of one tenth, so as to make 100 apertures in the square inch, explosion may take place, either from intense ignition of the top of the lamp, or from lateral currents of air forcing the flame through the interstices.
When the intervals of the same wire were only one fourteenth, though the danger from lateral motion was obviated, still ignition of the wire caused explosion. With intervals of one sixteenth, still there was danger from the same source; but when the distances were reduced to one twenty-fourth on 576 apertures in the square inch, then the lamp appeared safe, under all circumstances, in mixtures of coal gas and air.
With a view to explain the non-transmission of inflammation through small apertures, the author considers the nature of flame in general; and since a piece of phosphorus, or even a small taper, will burn in the midst of a large flame made by the combustion of alcohol, he is of opinion that oxygen exists in the centre of all flame, forming an explosive mixture with the vapour, but which burns solely at the exterior surface, because it is there alone sufficiently heated to take fire.
If a piece of wire-gauze be held in the flame of a lamp, or of coal gas, no flame passes through the gauze; for though a portion of the inflammable vapour passes, it loses too much heat in its passage to propagate the flame; but in the case of inflammable mixtures of coal gas entering a lamp, and burning at the interior surface, that which is exterior has not been exposed to any heating cause, and consequently is in no danger of taking fire at the sides of the lamp; and the results of combustion which escape at the top, though heated, are no longer inflammable.
In conclusion the author informs us, that these lamps have now been tried in two of the most dangerous mines near Newcastle with perfect success; and he has great hopes that they will shortly be adopted in many of the collieries in that neighbourhood.