of lighting the Mines so as to prevent its Explosion, 449 



and I cox'.id not make any mixture explode in a glass tube l-7th 

 of an inch in diameter: and this gas was more inflammable than 

 the fire-damp, as it consisted of cavburetted hydrogen gas mixed 

 with some defiant gas. 



In exploding mixtures of fire-damp and air in ajar connected 

 with the atmosphere by an aperture of half an inch, and con- 

 nected with a bladder by a stopcock, having an aperture of 

 about l-6th of an inch*, I found that the flame passed into the 

 atmosphere, but did not communicate through the stopcock, 

 so as to inflame the mixture in the bladder: and in comparing 

 the power of tubes of metal and those of glass, it appeared that 

 the flame passed more readily through glass tubes of the same 

 diameter ; and that explosions were stopped bv metallic tubes 

 of l-5th of an inchf, when they were If inch long; and this 

 phaenomenon probably depends upon the heat lost during the 

 explosion in contact with so great a cooling surface, which 

 brings the temperature of the first portions exploded below that 

 required for the firing of the other portions. Metal is a better 

 conductor of heat than glass : and it has been already shown 

 that the fire-damp requires a very strong heat for its inflamma- 

 tion. 



Mixture of the gas with air I found, likewise, would not ex- 

 plode in metallic canals or troughs, when their diameter was 

 less than the l-7th of an inch, and their depth considerable in 

 proportion to their diameter ; nor could explosions be made to 

 pass through such canals. 



Explosions likewise I found woidd not pass through very fine 

 wire sieves or wire gauze. 



I mixed azote and carbonic acid in different quantities with 

 explosive mixtures of fire-damp, and 1 found that even in very 

 small proportions they diminished the velocity of the inflamma- 

 tion. Azote, when mixed in the proportion of 1 to 6 of an ex- 

 plosive mixture, containing 12 of air and 1 of fire-damp, de- 

 prived it of its power of explosion; when I part of azote was 

 mixed with 7 of an explosive mixture, only a feeble blue flame 

 slowly passed tlirongh the mixture. 



1 part of carbonic acid to 7 of an explosive mixture deprived 

 it of the power of exploding ; so that its effects are more re- 

 markable than those of azote ; probably, in consequence of its 



* Since these experiments were made, Dr. WoIIaston has informeJ me, 

 that he and Mr. Tennaot had observfd some time ago, that mixtures of 

 tlif; gas from the distillation of coal and air would not explode in very 

 binall tubes. 



+ I do not give this result as perfectly exact, as the Lore of the metallic 

 tube had not the same polish as that of the tube of glass. 



Vol. 4G. No. 212. Dec. 1815. F f gneater 



