1816.] On the Ventilation of Coal-AMines. 291 
the point which has been found to admit the requisite supply.* 
These doors, or stoppings, may be made of light materials, as 
they are not intended to withstand the application of any consider- 
able force. In placing them there is only one rule to be observed, 
which is, that they must always be fixed in the lower opening of 
the passage, with regard to the general dip of the mine, and not 
in any higher part of it. Stoppings for instance, must not be put 
into the upper ends of the passages h, h, but into the lower extre- 
mities, as in the similar passages, 7,7. While these precautions 
are attended to, the stoppings can never, by any accident, become 
the means of accumulating the fire-damp. 
Recollecting then the rise of the mine, and the levity of the 
fire-damp, an attentive examination of the figure will show, that if 
the stoppings be judiciously placed, the passages clear, and the 
shafts open, no atmospheric air, much less inflammable air, can 
possibly stagnate, or accumulate, in any part of the workings. It 
will be observed, that the air, in this mode of ventilation is never 
turned down the slope, after having once ascended it; but that it 
invariably proceeds upward from the moment it begins to ascend, 
until it is discharged by the upcast shaft at D. It will also be evi- 
dent, that the circulating current is perfectly under our command ; 
and that the whole, or any part of it, may be excluded from, or 
admitted into, any part of the workings at pleasure. 
It does not seem necessary to say any thing more in illustration 
of the general principles; but it is proper to notice certain cireum- 
stances which may occur to interrupt or derange their operation. — 
The passages of a mine are frequently obstructed, and sometimes 
entirely stopped up, by falls of stones, and other matters, from the 
roof; when this happens, an accumulation of fire-damp, more or 
less extensive, must unavoidably take place; but, in the mode of 
working and ventilating, which it is the object of this. paper to ex- 
plain, the limits of such accumulations are accurately fixed. Let 
it be supposed for instance, that a fall.of the roof has occurred at 
K, so as to shut up the two passages /, 1, below it. It is obvious, 
that the fire-damp will gradually collect, until these two passages 
are filled with it down the slope, as far as to the next openings 
below: but whenever they are filled so far, the accumulation must 
stop; because, as fast as new supplies of fire-damp arrive, they 
will proceed up the passages, ™,m. It may be added, that the 
fire-damp,. having so many other passages to escape by, would, in 
ordinary circumstances, collect very slowly below the fall at K, 
and thus afford a greater chance of its being discovered by the per- 
* It is to be observed in fastening these doors at this point, that they are to 
open down the slope; and that the fastenings must be slight; merely sufficient ‘to 
keep the door in its proper position, and to give way so as to allow the door to 
shuton the application of a slightdegree of force. Their being accidentally shut 
cannot produce any had effects, as no fire damp can acenmulate either above or 
below them. The only inconyenience will be 4 temporary derangement of the 
atmospheric current, : 
