Clifton College Sdentific Society. 19 



SAFETY LAMP. 



The last thing I have to mention to-night is an improvement in the 

 Da^-y Safety Lamp. But for the rashness of the miners in exposing 

 the bare flame, the present Lamp -would be suflicient to secure the 

 miner fi-om danger, under certain conditions. Only lately it has been 

 proved experimentally, by Mr. Galloway, that a sound-wave is capable 

 of driving the flame through the gauze ; there is, therefore, an end of 

 the Davy Lamp as a Safety Lamp. A sound-wave may be caused by 

 the firing of a gun, or by blasting coal. Tlie miners have themselves 

 to thank for many of the explosions ; they often open their Lamps, 

 either to get a light for their jjipes or to get a stronger light to work 

 by. But although the plan of locking the Lamps has effectually 

 prevented the former practice, yet the miner still obtains a light for 

 h's pipe by a simple but dangerous device. He tilts the Lamp till 

 the flame plays on the gauze, or makes it red hot ; and there cannot 

 be much doubt that in some cases it has resulted in disaster. 

 Notwithstanding the precautions taken for their safety, both by the 

 government and their employers, no less than 400 miners lose their 

 lives annually, and in almost every case through the carelessness of 

 one of their number. The principle on which the Davy Safety Lamp 

 is based is this : — A gas will not ignite until raised to certain 

 temperature. So if an explosive gas is separated ti'om a flame by wire 

 gauze which conducts away the heat too fast to allow the gas to be 

 raised to that temperature, it will not ignite. Davy, in his Safety 

 Lamp, used a small oil lamp, and surrounded its flame by a cylinder 

 of gauze about four inches in diameter, and having about 700 meshes 

 to the square inch. 



When fire damp, which is a compound of Carbon and Hydrogen, 

 and which becomes a very explosi^^e gas when mixed with about eight 

 times its volume of air, comes in contact with the Lamp, it passes 

 thi-ough the gauze and burns inside the Lamp, but cannot set fire to 

 the gas outside because the wire gauze conducts away the heat too 

 fast to allow ignition to take place.. The only effect the slight 

 explosion inside has, is to warn the miner to seek a place of greater 

 safety. From what I have said before, it w-ould appear that the Safety 

 Lamp, in its present state, is not complete. The essential ]5oints for 

 a Safety Lamp, then, may be stated in the follomng conditions : — 

 It must be proof against over-heating by its own flame. It must give 

 the maximum amount of light, and when trimmed it must be secure 

 from all tampering ; and also it must have a flame so ^'ell protected 

 as not to be influenced l:)y sudden currents or sound-waves. These 

 conditions are tolerably well carried out in JMueseler's Lamp, in which 

 the bottom portion of the gauze is replaced by a cylinder of stout 

 glass, -while a mptal chimney over the flame creates a draught strong 

 enough to keep the glass comparatively cool, and insures perfect 

 combustion. This Lamp, however, is liable to accident through the 

 breaking of the glass. Among the numerous designs that have 

 recently appeared, probably the best is that patented by Mr. Yates. 



