Instruction on the uses of the Davy lamp to all colliers
The following remarks were suggested on frequently witnessing the indifference with which the colliers, while at work seem to treat the necessary precautions for their safety, especially with regard to the firedamp. This gas which is constantly disengaged during the working of coal, was an almost insurmountable obstacle to the working of many of our collieries until the discovery of the safety lamp by Sir Humphry Davy about 25 years ago.*
The safety lamp, the miner's best friend, will briefly explained by its nature and properties, in the hope that the consideration of it may induce many of you to prize more highly one of the most important benefits that ever humanity derived from science.
The flame of the safety lamp is surrounded by a gauze cylinder, made of iron or copper wire. The spaces between the wires should never exceed one twenty-fourth part of an inch or in other words, there should always be, at least, 24 of those spaces in the length of one inch in every part of the gauze, for this reason, that the flame or blaze will not pass through the wire gauze at or above that fineness, but through coarser it will. This is the sole principle of the safety lamp and one which the colliers ought always to bear in mind
Should the gauze be courser, or of fewer spaces than 24 to one inch, the lamp would be useless as a protection, should the be much finer, sufficient light would not be emitted to enable the miner to work.
You ask, how it prevents the explosion of the gas outside the gauze? It is because the wire absorbs or takes a way the heat of all flame that approaches or comes between them when the flame is divided by a gauze of the above texture but which would not be the case were the distances between the wire greater than specified, owing to the quality of the flame which would be less divided overcoming the power of the wire to conduct away the heat, consequently the flame or blaze would pass through the gauze and explode the gas outside the lamp.