HYDROGEN. 51 



in the upper part of the mine, on account of its 

 lio-htness, but does not mix there with atmospheric 

 air, unless some agitation takes place. The miners 

 frequently set fire to it with a candle, laying, at 

 the same time on their faces, to escape the violence 

 of 'the shock. An easier and safer method of 

 clearing the mine is, by leading a long tube 

 through the shaft of it to the ash-pit of a furnace ; 

 by this means the gas will be conducted to feed 

 the fire. 



Hydrogen gas, though itself inflammable, extin- 

 guishes burning bodies, and is incapable of main- 

 taining combustion. Bring an inverted jar filled 

 with hydrogen gas over the flame of a candle, and 

 depress the jar, so that the lighted wick may be 

 wholly surrounded by the gas 5 the candle will be 

 immediately extinguished. 



Hydrogen gas is only inflammable when in con- 

 tact with atmospheric air or oxygen gas. Fill a 

 small phial with hydrogen gas, and take it from 

 the pneumatic trough, placing the thumb on the 

 mouth thereof, to prevent the gas from escaping ; 

 if a lighted taper be applied to the mouth of the 

 phial, the gas will take fire, and burn with a lam- 

 bent flame. The gas will only burn where it is in 

 contact with the atmospheric air ; the flame will 

 descend gradually, till all the gas is consumed. 



If the hydrogen gas be pure, the flame will be of 

 a blue colour ; but if the gas holds any substance 

 in solution, which is generally the case, the flame 

 is tinged of different colours, according to the sub- 

 stance. It is usually reddish, because the gas 

 holds in solution a little charcoal. 



On this principle i? constructed the philosophical 

 candle, which cannot be easily blown out. Fill 

 with hydrogen gas a bell glass, furnished with a 



E 2 



