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 part 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 gradaal, it will not exert its full deleterious. 
power, but produce only such effects as will give warning of its. 
presence, 
Even before it acts this far, it will be eee 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 peraiee ; and this criterion. must be- 
come still more evident, when the person exposed to it js. 
guarded from its early explosion, and it is thus allowed to ac-. 
cuiiplaic 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 aight 
as a criterion, though, in- the usual mode of applying it, it 
seems to be a very hazardous one,—what is called the candle 
tope. 
