of lighting the Mines so as to prevent its Explosion. 455 



©f only -^ of an inch in circumference ; and a number of aper- 

 tures of -pi^ of an inch are sufe when their depth is equal to their 

 diameter. It is evident from these facts, that metallic doors, or 

 joinings in lamps, may be easily made safe by causing them to 

 project upon and fit closely to parallel metallic surfaces. 



Longitudinal air canals of metal may, I find, be employed 

 v.'ith trie same security as circular canals ; and a few pieces of 

 tin-plate soldered togetlier with wires to regulate the diameter 

 of the canal, answer the purpose of the feeder or safe chimney 

 as well as drawn cylinders of brass. 



A caudle will burn in a lantern or glass tube made safe with 

 metallic gauze, as well as in the open air : I conceive, however, 

 tiiat oil lamps, in which the wick will always stand at the same 

 height, will he prefeo-red. 



But the principle applies to every kind of light, and its entire 

 •safety is demonstrated. 



^Vhen the fire-damp is so mixed with the external atmosphere 

 as to render it explosive, the light in the safe lantern or lamp will 

 be extinguished, and warning will be given to the miners tQ 

 withdraw from, and to ventilate that part of the mine. 



If it be necessary to be in a part of the mine where the fire- 

 damp is explosive, for the purpose of clearing the workings, 

 taking away pillars of coal, or other objects, the workmen may 

 be lighted by a fire made of charcoal, which burns without fiame, 

 or by the steel -mill, though this does not afford such entire se- 

 curity from danger as the charcoal fire. 



It is probable, that when explosions occur from the sparks 

 from the steel mill, the mixture of the fire-damp is in the pro- 

 portion required to consume all the oxygen of the air, for it is 

 only in about tliis proportion that explobive mixtures can be fired 

 by electrical sparks from a common machine. 



As the wick may be moved without ecmmunication between 

 the air in the safe-lantern or lamp and the atmosphere, there is 

 no d iu^er in trimming or feeding them ; but they should be 

 lighted in a part of the mine where there is no fire-damp, and 

 liy a person charged with the care of the lights j and by these 

 inventions, used with such sim|)le precautions, there is every 

 reason to believe a number of lives will be saved, and much 

 misery prevented. Wliere candles are employed in the open air 

 in the mines, life is extinguished by the explosion ; with the safe 

 lantern or safe lamp, the light is only pvit out^ and no other iii- 

 convcnience will occur. 



Amongst various plans for preventing accidents from the fire- 

 damp, it has been proposed to burn the fire-damp in the mine ; 

 but this will only render the ventilation more difficult ; for there 

 will be less rcspirabie air in the residuuni of the combustion than 

 Ff4 in 



