288 On the Ventilation of Coal-Mines. (APRIL, 
But this peculiarity was doubtless impressed on this substance for 
other and more important purposes. It presents itself as the means 
of getting rid of the gas in situations where it is evolved, or accu- 
mulated in dangerous quantities ; and with the intention of assuming 
this striking property of inflammable air as a fundamental principle 
in ventilation, it is necessary to adduce some evidence in support of 
what has already been said concerning it. . ) 
In the Annals of Philosophy for the month of June, 1814, at 
. 435, the following passages occur :— 
‘¢ I wish the proprietors of coal-mines would turn their attention 
to some circumstances which, if duly attended to, would enable 
t1em completely to put an end to the disastrous effects of explo- 
sions of fire-damp in their mines. These circumstances are the 
following: —1. Explosions of fire-damp are confined to deep 
coal-mines, and never happen in those at no great distance from 
the surface of the ground. ‘Thus nobody ever heard of such explo- 
sions in the neighbourhood of Edinburgh or Glasgow ; but about 
Borrowstoness, where the mines are deep, they occur as well as in 
England. 2. The specific gravity of carbureted hydrogen gas is 
only 0°555, or a very little more than one-half of the specific gravity 
of common air. 3. Jf you let go ever so much carbureted hydrogen 
gas in a room with an aperture at the roof, and examine the air of 
the room half an hour after, no traces of the carbureted hydrogen 
will be detected. 4. Carbureted hydrogen will not explode unless it 
amounts to =!,th of the bulk of the,common air with which it is 
mixed. The unavoidable conclusion from these facts is, that if the 
fire-damp accumulates in coal-mines so as to explode, it is only 
because circumstances prevent it from making its escape with sufhi- 
cient rapidity. Hence it follows that the defect lies in the mode at 
present employed to ventilate coal-mines; and that if the mines 
were ventilated according to the well-known principles of hydrau- 
lics, no explosions would ever take place. 
“* To prevent the evolution of fire-damp I conceive to be impos- 
sible ; to attempt to destroy it when formed, as has been sometimes 
proposed, is quite absurd; but allow it to make its escape from the 
mine without obstruction, and it will occasion no inconvenience 
whatever.” 
Having so far explained the principles to be employed, it now 
remains to show how they may be combined, so as to secure their 
constant operation in ‘letting ” the fire-damp “ escape with sufh- 
cient rapidity,” and “ without obstruction.” : 
Referring, then. to the description of the strata already given, 
your readers will readily perceive that Fig. 1, Plate XLVIL., is 
intended to represent a perpendicular section of a field of coal in 
the direction of the dip and rise, in which B, C, D, show pretty 
nearly the direction of the inclining stratum of coal, though the 
thickness is enlarged beyond its due proportion, on aceount of the 
smallness of the scale. 
A represents a pit, or shaft, sunk to the coal on its south-casterm, 
