AND PREVENTING ITS EXPLOSION- 37 
One principal difficulty in contriving any safe mode of light- 
ing coal-mines, must be that of having moveable lights ;. for 
these the workmen will often: find it necessary, and in ge- 
neral will be desirous, to employ. This may be easily attain- 
ed by connecting with the bottom of the case or lantern, a 
flexible tube, air-tight or nearly so, which may be done by a 
tube of prepared leather varnished ; this tube being of such a 
length as to reach nigh to the floor. The lamp can thus be 
held in the hand, or attached to.any occasional support. Fig. 2. 
represents a lamp of this. kind. 
No danger, or scarcely any, I conceive, can arise in the use 
of this apparatus. If the size of the upper aperture be duly 
adjusted, no air cam enter by it to the lamp, for the current of 
heated air will prevent this. And this air can never be:heated. 
so high:as.to. kindle any mixture of carburetted hydrogen: 
No inflammable air can. enter from the-hottom; so as to be- 
capable of kindling, for the reason already assigned, that from. 
its levity it rises to the roof:of the mine, and the mixture of it 
with atmospheric air, which is explosive, is always accumulated 
there. Nor can this increase so as to extend to the floor of the. 
mine, and the miner remain present, as, previous to this, the: 
effect of this mixed air, received by respiration, would be felt, 
and give warning of the danger. (Note C.) 
The flexible tubes of the moveable lamps may be easily pre- 
pared, and preserved air-tight : and there being so ready a sup-- 
ply of air from below, if there were any minute fissure in the. 
sides of the tube, no air would enter by it, or the quantity. 
would be so small, and so much, diluted by intermixture, that 
there could be no risk. In the fixed lamps, having an iron or 
copper tube: conveying the air, there could be no risk of this 
kind, and if it were necessary, similar metallic tubes, with 
moveable circular joints, could be adapted to the moveable; 
lamps. 
There 
