before 1733 had been tried with limited success. An example of a Spedding steel mill may be seen in the museum at Whitehaven where Spedding was manager of the collieries of Sir James Lowther, 4th Baronet. A steel disk was rotated at high speed by a crank mechanism. Pressing a flint against the disk produced a shower of sparks and dim illumination. These mills were troublesome to use and were often worked by a boy, whose only task was to provide light for a group of miners. It was assumed that the sparks had insufficient energy to ignite firedamp until a series of explosions at Wallsend colliery in 1784; a further explosion in June 1785 which the operator of the mill (John Selkirk) survived showed that ignition was possible. The first safety lamp made by William Reid Clanny used a pair of bellows to pump air through water to a candle burning in a metal case with a glass window. Exhaust gases passed out through water. The lamp gave out only a weak light though it was intrinsically safe provided it was kept upright. It was heavy and ungainly and required a man to pump it continuously. It was not a practical success and Clanny subsequently changed the basis of operation of later lamps in the light of the Davy and Stephenson lamps. Oil lamps Principles of operation Safety lamps have to address the following issues: Provide adequate light Do not trigger explosions Warn of a dangerous atmosphere Fire requires three elements to burn: fuel, oxidant and heat; the triangle of fire. Remove one element of this triangle and the burning will stop. A safety lamp has to ensure that the triangle of fire is maintained inside the lamp, but cannot pass to the outside. Fuel there is fuel in the form of oil inside the lamp and fuel in the form of firedamp or coal dust outside. Oxidant there is an oxidant in the form of air present outside the lamp. The design of the lamp must allow the oxidant to pass into the lamp (and therefore exhaust gases to escape) or else the lamp will extinguish. Heat heat can be carried by the exhaust gases, through conduction and through burning of firedamp drawn into the lamp passing back down the inlet. Control of the transfer of heat is the key to manufacturing a successful safety lamp. In the