42 ON THE FIRE-DAMP OF COAL-MINES, 



is attended with :ess trouble, and requires less attention than 

 any other that can be used. 



Some precautions may be necessary in kindling the candles 

 or lamps. In the moveable apparatus this may be done at the 

 bottom of the shaft, or any other pail of the mine where the 

 air must be pure. The fixed lamps may be kindled in a simi- 

 lar manner, being supplied with a flexible tube at the bottom,, 

 to be removed when they are transferred to the fixed tube, and, 

 if necessary, with the additional precaution of stop-cocks to 

 each. Various arrangements with regard to these will readily 

 occur. (Note D.) 



I have said that the accumulation of the carburetted hydro- 

 gen in the air of the mine, may be discovered by its effect 

 on respiration. Its deleterious agency is well known. At the 

 same time as in the greater number of situations, its addition 

 to the air must be gradual, it will not exert its full deleterious 

 power, but produce only such effects a3 will give warning of its 

 presence. 



Even before it acts this far, it will be apparent by its smell. 

 Hydrogen in a humid state has a sensible odour. The fire- 

 damp in mines is known by its smell ; the miner, in judging of 

 its presence, always advancing with considerable confidence 

 when no smell is to be perceived ; and this criterion must be- 

 come still more evident, when the person exposed to it is 

 o-uarded from its early explosion, and it is thus allowed to ac- 

 cumulate to a greater extent. It is also sometimes apparent 

 to the eye, by the vapour which is diffused through it, forming 

 a kind of mist, floating under the roof of the mine, and fluctu- 

 ating with every movement of the air. 



There is one other circumstance which has been employed 

 as a criterion, though, in the usual mode of applying it, it 

 seems to be a very hazardous one, — what is called the candle 



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