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danger to be apprehended from the neglect of trap-doors being 
left open or shut ; the air is split, and sent up each board-gate 
just in the proportion required, by air gauges or splitters fixed 
in the counter level at the foot or lower end of each board- 
gate, and with these the hurriers or trappers have nothing to 
do. The only trap-doors the hurriers have to pass through 
is one fixed in the slit betwixt the counter and working levels, 
opposite each board-gate, and these are made to close of 
themselves as soon as the trams pass through. 
In conclusion, Mr. Brakenridge entered into some cal- 
culations to prove that, upon these principles, a mine may 
be worked with a saving of expenses to the coal proprietors ; 
and he asserted his entire confidence that those heart-rending 
scenes of destruction to the property and lives of our 
fellow-creatures, which we have recently had so much cause 
to lament and deplore, would, in a great degree, be averted. 
At the conclusion of this paper an interesting discussion 
followed, in which 
Mr. Carter said he quite concurred in the general 
principles of Mr. Brakenridge, and regarded it as a 
remarkable fact that Mr. Brakenridge and himself, though 
unknown to each other, should have been labouring simul- 
taneously to develope a perfectly identical system of working 
collieries. Those who were present at the Barnsley meeting 
would remember that the paper he there read, enunciated a 
principle identical with the one now introduced by Mr. 
Brakenridge; but Mr. Brakenridge had now more fully 
and clearly elaborated the principle. 
Mr. Briggs thought Mr. Brakenridge had not made 
any provision for " throws," or fractures of the stratum. 
A practical difficulty would be found in the 120 yards wide 
working. Each would require twelve men to work abreast ; 
these men would be in each other's way ; they would have 
