32 



are of smaller dimensions, one with a pair of small bellows, and the 

 other with a syringe ; but both of these, like the steel mill, require a 

 person to work them constantly, and will probably be superseded by 

 the simple construction first described. 



An Account of an Invention for giving Light in explosive Mixtures of 

 Fire-damp in Coal Mines, by consuming the Fire-damp. By Sir 

 Humphry Davy, LL.D. F.R.S. V.P.R.I. Read January 11,1816. 

 [PAi7. Trans. 1816,^.23.] 



This contrivance consists in covering the flame of any lamp or can- 

 dle with a wire sieve, the apertures of which may be as large as Vvth 

 of an inch square. 



When a cylinder of wire gauze, covered at top with the same gauze, 

 is closely fitted to a lamp, and surrounds its flame so that there is no 

 aperture but those of the gauze, if the little lantern so constructed 

 be introduced into the most explosive mixtures of carburetted hydro- 

 gen and air, the cylinder becomes filled with a bright flame at its in- 

 terior surface, which continues to burn as long as the mixture remains 

 explosive. 



When the carburetted hydrogen constitutes no more than n Vth of 

 the mixture, the flame of the wick continues to burn surrounded by 

 the flame of the fire-damp ; but when the proportion is as 1 to 7, the 

 flame of the wick disappears. 



When the apertures of the gauze are of the largest size, the flame 

 is the most brilliant, and the wire of which it consists becomes ignited, 

 but still without occasioning explosion of the mixture external to the 

 lamp. 



Similar experiments were also made with hydrogen (not carbu- 

 retted), and with the same results. But in this case the gauze was 

 of the finest kind, with 6400 apertures in the square inch ; and since 

 the thickness of the wire was -s-hrth of an inch, the apertures them- 

 selves were about -rfu-th of an inch square. With gauze of this con- 

 struction a flame may be introduced even into a mixture of hydrogen 

 and oxygen, and burn this mixture at the inner surface of the lan- 

 tern, without communicating its flame to the mixture externally, 

 even though the wires become intensely red hot. 



After such trials of the security of this little apparatus, the author 

 has no hesitation in recommending it for adoption by the collier, who 

 will require for his security nothing more than a little wire cage to 

 surround the flame of his lamp, and thus, at the cost of a few pence, 

 will procure a light as long as there is a sufficient supply of fire-damp, 

 without any further expense. 



