FLAME. 63 



contact with its outer edge, and is frequently 

 *'snuiFed out" merely in consequence of its being 

 cooled. A candle, moved quickly through the air, 

 flares and smokes, and its combustion becomes im- 

 perfect, because it is cooled. 



99. It is a necessary consequence of this fact, 

 that flame cannot pass through a piece of wire-gauze, 

 and the miner's safety-lamp merely consists of a lamp 

 surrounded with a cylinder of wire-gauze. A lamp 

 thus protected, may safely be taken into an explosive 

 mixture of air and carburetted hydrogen, the flame 

 may be put out, the explosive gas may burn within 

 the cylinder, but the flame cannot pass through the 

 wire gauze to set fire to the explosive atmosphere 

 without, because it is too much cooled by contact 

 with the wire gauze. 



100. It is evident that the combustion of a flame 

 can only take place on its outside, or at that part at 

 which it is in contact with the air, and, as a necessary 

 consequence of this, it follows that flame is hollow. 

 It is only the outside of the flame of a candle that 

 gives out light, the inside is dark, because no com- 

 bustion is there going on. In a large flame this is 

 easily shown, because, as no combustion is going on, 

 no heat is given out, and consequently the inner 

 part of such a flame is comparatively cool; a small 

 piece of wood or paper may be held in the centre of 

 such a flame, and it will hardly be singed, or a small 

 spoon containing a portion of gunpowder may be 



