the candle is raised the tip is observed and if unchanged the atmosphere is safe. If however the tip turns bluish-gray increasing in height to a thin extended point becoming a deeper blue, then firedamp is present. Upon detecting firedamp the candle is lowered and arrangements made for the ventilating of the area or the deliberate firing of the firedamp after the end of a shift. A man edged forward with a candle on the end of a stick. He kept his head down to allow the explosion to pass over him, but as soon as the explosion had occurred stood upright as much as possible to avoid the afterdamp. Officially known as a fireman he was also referred to as a penitent or monk from the hooded garb he wore as protection. The protective clothing was made of wool or leather and well dampened. As can be imagined this procedure did not always preserve the life of the man so employed. When they came into regular use, barometers were used to tell if atmospheric pressure was low which could lead to more firedamp seeping out of the coal seams into the mine galleries. Even after the introduction of safety lamps this was still essential information, see Trimdon Grange for details of an accident where pressure was involved. The lack of good lighting was a major cause of the eye affliction nystagmus. Miners working in thin seams or when undercutting the coal had to lie on their side in cramped conditions. The pick was swung horizontally to a point beyond the top of their head. In order to see where they were aiming (and accurate blows were needed), the eyes needed to be straining in what would normally be the upwards and slightly to one side direction. This straining led first to temporary nystagmus and then to a permanent disability. Mild nystagmus would self-correct if a miner ceased to perform this work but if left untreated would force a man to give up mining. The lower levels of light associated with safety lamps caused an increase in the incidence of nystagmus. First attempts at safe lamps Both on the continent of Europe and in the UK dried fish skins were used. From them a faint bioluminescence (often called phosphorescence) occurs. Another safe source of illumination in mines was bottles containing fireflies. Flint and steel mills introduced by Carlisle Spedding (1696-1755)