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an explosion, are prevented from obtaining fresh air or the 
means of exit. 
5th. A greater facility for working the mine, by the 
removal of a number of the traps ; a great saving in the 
expense of working, by a less number of trappers being 
required, thus giving the children of the colliers a better 
opportunity of acquiring a school education, by removing the 
temptation of a few shillings per week, for which the poor 
children are consigned to a dark, solitary, and monotonous 
employment. 
6th. A larger proportion of the foul air will be drawn off, 
as the opening being made in the upper parts of the mine 
will give the carburetted hydrogen the advantage of its 
lower specific gravity. I may here remark that where a 
quantity of carbonic acid gas is eliminated, I should place 
openings beneath the levels of the main airways, so as to 
give it the advantage of its higher specific gravity. 
7th. By the circulation of air in the goaf, the spontaneous 
combustion of the coal dust, (a frequent occurrence in some 
districts abounding in iron pyrites,) causing accidents of 
serious consequence both to life and property, would be 
prevented. 
It is possible that the free passage of air through the goaf 
may be impeded by the falling of the roof of the mine, in 
which case one of the branch roadways must be trapped and 
made an upcast roadway, the necessary communication being 
made overhead with the main upcast windway. 
The plans I have thus endeavoured to explain do not 
involve any costly contrivances, they, indeed, have, I believe, 
claims to consideration on the ground of expense, as the 
process of insulation and circulation could be effected more 
economically than at present, the ventilation being carried on 
quite automatically so long as the upcast shaft has a rising 
current of sufficient strength. But even should I have mis- 
