The "safety lamp" invented by Humphrey Davy in 1815 utilised the cooling effect of metal gauze to prevent the flame of a candle or oil lamp (essential for illumination in mines) from passing through such a screen. It is therefore rendered unable to ignite any potentially explosive mixture of air and methane in the atmosphere surrounding the lamp. A number of experimental demonstrations are detailed to illustrate this effect, and show how the lamp could also indicate the presence of methane in the air of a coal mine.