634 
feet per minute. This would be sufficient for most of the 
large collieries in the South Yorkshire coal-field, and could 
be arranged, according to circumstances, as to sub-divisions, 
&c. &c. The currents could not be much diminished, except 
by friction, if the area of fifty feet were maintained in each 
division in the workings — as there would be little loss from 
leakage, the barriers being throughout the whole circuit of 
the air, of solid coal, except at the over-throws — and in order 
to provide for this there would be an extra level the whole 
distance, five being necessary for the first division ; but I 
think this is preferable to the risk of the stoppings being 
blown out should an explosion take place, and would not 
incur much extra cost, as the coal got out would pay for 
the yards in strait work. I think that what is here proposed 
is easy to effect in every existing colliery, the over-throws 
and dumb drifts being the chief expense. From £300 to 
£400 would cover the whole, and secure a good ventilation, 
with the furnace at hand that could be conveniently got to in 
all emergencies ; and all the roads could be well sustained 
until the whole field of coal was exhausted. 
But I must draw to a close, as it is impossible to enter 
into all the necessary details of working and ventilation in 
a single paper ; but I would add, in conclusion, that if it 
is not possible to avoid explosions altogether, it is within the 
range of possibility to lessen the danger of explosion, and 
also the injurious effect of any explosion which may occur. 
These results cannot be accomplished without an ample and 
constant supply of air, a good plan for the distribution of 
the same through the entire workings, properly constructed 
furnaces, large heating surface, good dumb drifts, sufficient 
openings into the up-cast shaft, and shafts of sufficient 
capacity ; trusty fire-men and furnace men, steady and 
vigilant discipline, and strict attention on the part of all in 
office ; and when all combine to ensure safety, then, and only 
