§2° ON THE FIRE-DAMP OF COAL-MINES} 
sive, uniformly take place, as all the facts connected with the 
state of the air in the mines prove; nor can any accumulation 
of it take place, which shall reach the floor of the mine, but by. 
its filling the space from the- roof downwards, mixed more or 
Jess with the atmospheric air. All that is necessary, therefore, 
is to guard against the chance, extremely small in itself, of the: 
open end of the tube being in the direction of a stream of the 
gas, if at any time it should issue from the floor, and this is, 
easily done by the methods stated in the descriptions, of the, 
tube being turned up at its extremity, or of its being closed for, 
the height of two or three inches, with apertures above this 
height, to-admit the air. Any small quantity which might be 
brought by the current of air entering the tube must be unim- 
portant, and any danger from this source must require such.a 
combination of circumstances as may well be expected never 
to occur,—that of the tube being in the direction of the cur- 
rent of gas,—of the mixture of it. with atmospheric air being in 
that limited proportion when it reaches the flame of the lamp 
in which it explodes, and of the whole air at the floor of the 
mine being also in that state in which it will explode; and 
all this independent of the circumstances, that by any such 
mixed air passing into the lantern, the flame of the lamp will 
be extinguished’ instead of explosion happening, and that ex- 
plosion, even if it did oecur, would not be conveyed along this 
length of tube. 
“The same arrangement, with regard: to. the tube, obviates 
another possible inconvenience;—that of the: entrance of car- 
bonic acid gas, which, from its greater specific gravity, may 
sometimes occupy the floor of the mine. It seems scarcely 
ever to be accumulated to this extent in mines in which fire- 
damp is generated ; and if it were, its entrance into the lan- 
tern, would be productive of no other accident than that of 
extinguishing 
