
TRANSACTIONS OF THE SECTIONS. 113 
It has been objected that machinery of any kind, from its liability to fracture or 
derangement, is inappropriate to the ventilation of a colliery ; but this broad objec- 
tion is daily overruled. To machinery, in a much more complex form, we commit 
ourselves with confidence to be carried by land at the rate of fifty miles per hour, 
or conveyed across the Atlantic. But where this objection may yet prevail, an ad- 
ditional or spare cylinder, with its appendages, may be attached to the opposite end 
of the frame ready to be applied if necessary. A suspension of the revolving of the 
ventilator would not be attended with immediate danger, for it offers no resistance 
to the ascending current, which would coatinue long enough for the men to with- 
draw from the pit, and repairs would be performed with less loss of time than is 
the case in the repair of furnaces. 
With respect to cost, a ventilating machine with steam-engine complete, suited to 
an extensive colliery, can be supplied, erected, and put to work for about £350; 
and where there are suitable boilers already at the colliery from which steam can 
be obtained, the cost would little exceed half the above sum. Lastly, with respect 
to the power of rarefaction, the maximum effect of the furnace under the most 
favourable circumstances gives 123, whilst with the apparatus at Gelly Gaer 24 lbs. 
on the square foot has been produced. 
But beyond the mere substitute for the furnace as applied to all the ordinary 
purposes of ventilation, the ventilating machine possesses advantages to which the 
furnace has no applicability. One of these is, that in the event of an explosion, the 
machine being on the surface, and placed with respect to the upcast shaft out of 
the reach of injury, can be immediately applied to clearing the pit of the choke 
damp consequent on explosion, and thus save the lives of men which would other- 
wise be lost. 
Another, and what the author esteems by far the most important peculiarity pos- 
sessed by the machine is, that it has such power of rarefaction that the atmosphere 
of a colliery may be subjected in half an hour to an artificial exhaustion of three-, 
four- or five-tenths of an inch of mercury, producing in the colliery, during the 
absence of the workmen and their lights, the very same exudation of the gases that 
would have taken place during the natural change of the atmosphere indicated by a 
like fall of the barometrical column ; and before the men re-enter the mine the ma- 
chine will discharge the noxious gas by a current of fresh air more copious and 
effective than can be produced by any other means in use. All that is needful to 
effect this is, upon the retirement of the workmen and their lights that the air 
be prevented entering the workings from the downcast shaft; the exhaustion al- 
luded ‘to will immediately commence, for the quantity of air ascending the upcast 
shaft being decreased, the drum will be accelerated, and the whole extent of the 
workings will thus be subjected in a few minutes to the full measure of rarefaction 
obtained in the upcast shaft; upon the fresh air being permitted to enter, the colliery 
will be found in a state of extraordinary purity of atmosphere, and freedom from 
the risk of explosion. 
It is the concurrent testimony of all intelligent underground men, that the fire- 
damp exudes copiously during the fall of the barometer, and also that during its rise 
the reverse takes place* ; the fissures that during the fall were discharging gas, now 
absorb or draw in atmospheric air; but the effects attendant upon a fall of the 
barometer must necessarily be more or less dangerous, in proportion to the time it 
has been rising or nearly stationary, when a large portion of the gas evolved during 
that period will have accumulated in the goaf-basins or vaults. 
From these observations it is obvious, that if the fire-damp be drawn off at short 
intervals, as at every twenty-four hours, the accumulation and consequent danger 
will be very little, compared with what it frequently is through the continuance of 
_ weeks of fine weather; and the daily discharge of these minor accumulations will 
maintain the colliery whilst the men are at work in that state of safety experienced 
whilst the barometer is rising (see Messrs. Lyell and Faraday on the Goaf, p. 17). 
Possessing thus the power of anticipating the sudden exudation of gas by draw- 
ing it off when it can do no harm, and of rendering the colliery much more safe ‘and 
healthy for the workmen, may we not reasonably hope that the subject will receive 
the attention it deserves, and that a system of alternate exhaustion and restoration 
* This remark must not be applied to fire damp, which issues from whole coal under pressure. 
1 849. 8 
