Safety lamp it. Air is drawn in and descends just inside the glass, passing up through the flame in the centre of the lamp. The outer casings of lamps have been made of brass or tinned steel. If a lamp bangs against a hard piece of rock a spark could be generated if iron or untinned steel were employed. Within months of Clanny's demonstration of his first lamp, two improved designs had been announced: one by George Stephenson, which later became the Geordie lamp, and the Davy lamp, invented by Sir Humphry Davy. Subsequently, Clanny incorporated aspects of both lamps and produced
Safety lamp the Stephenson lamp was easily broken, and allowed the flame to ignite firedamp in the mine. Later Stephenson designs also incorporated a gauze screen as a protection against glass breakage. Developments, including the Gray, Mueseler and Marsaut lamps, tried to overcome these problems by using multiple gauze cylinders, but glass remained a problem until toughened glass became available. Were the flame to go out in a lamp, then there was a temptation for the collier to relight it. Some opened the lamps to light tobacco pipes underground. Both of these practices were strictly forbidden; they clearly negated the whole point