(f lighting the Mines so as to prevent its Explosion. 453 



gand lamps made on the same principle, the chimney being of 

 glass covered with a metallic top containing the safety canals, 

 and the air entering close to the flame through the circular 

 canals. 



The third kind of safe lamp or lantern, and which is by far 

 the most simple, is a close lamp or lantern into which the air is 

 admitted, and from which it passes, through apertures covered 

 with brass wire gauze of -^^ of an inch in thickness, the aper- 

 tures of which should not be more than -f4-g- of an inch ; this 

 stops explosions as well as long tubes or canals, and yet admits 

 of a free draught of air. 



Having succeeded in the construction of safe-lanterns and 

 lamps, equally portable with common lanterns and lamps, which 

 afforded sufficient light, and which bore motion perfectly well, 

 I submitted them individually to practical tests, by throwing 

 into them explosive atmospheres of fire-damj) and air. By the 

 natural action of the flame drawing air through the air canals, 

 from the explosive atmosphere, the light was uniformly extin- 

 guished ; and when an explosive mixture was forcibly pressed 

 into the body of the lamp, the explosion was always stopped by 

 the safety apertures, which may be said figuratively to act as a 

 sort of chemical Jire sieves in separating flame from air. But I 

 was not contented with these trials, and I submitted the safety- 

 canals, tubes, and wire gauze fire-sieves, to much more severe 

 tests : I made them the medium of communication between a 

 large glass vessel filled with the strongest explosive mixture of 

 carburetted hydrogen and air, and a bladder ^ ov ^ full of the 

 same mixture, both insulated from the atmosphere. By means 

 of wires passing near the stop-cock of the glass vessel, I fired 

 the explosive mixture in it by the discharge of a Leyden jar. 

 The bladder alwavs expanded at the moment the explosion was 

 made ; a contraction as rapidly took place ; and a lambent flame 

 played round the mouths of the safety apertiues, open in the 

 glass vessel ; but the mixture in the bladder did not explode: 

 and by pressing some of it into the glass vessel, so as to make it 

 replace the foul air, and subjecting it to the electric spark, re- 

 peated explosions were produced, proving the perfect security 

 of the safety apertures; even when acted on by a much more 

 powerful explosion than could possibly occur from the introduc- 

 tion of air from the mines. 



These experiments held good, whatever were the proportions 

 of the explosive mixture and whatever was the size of the glass 

 vessel, (no one was ever used containing more than a quart,) 

 provided as many as 12 metallic tubes were used of y of an inch 

 in diameter, and 2\ inches long; or provided the circular me- 

 tallic canals were -j'- of an inch in diameter, \'\ oi an inch 



F f 3 dcop, 



