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economical haulage and adequate ventilation. Corners and 
projections in the sides and roof of the roads, should be avoided 
as much as possible, for if the roof is irregular, you will see 
by observing the line along which the air travels, as shown 
in my illustration marked fig. 1, that these cavities above 
you, do not get any ventilation except by an artificial arrange- 
ment of brattice cloth. Carburetted hydrogen gas, being 
lighter than air, ascends and accimiulates in these places, 
therefore the more regular in shape you can keep your 
roads, and the safer and more economical it is. 
"Where two returning currents of air join each other, the 
junction should not be made at right angles, as is shown in fig. 
2, and as is usually the case, but efiected in the manner illus- 
trated in fig. 3, where you will observe that the two currents, 
at the point of junction, have both the same direction, and 
therefore assist each other, instead of the objectionable plan 
of meeting at right angles, where one current must naturally 
impede the course of the other. 
In pillar and stall workings there is the absence of this 
valuable current of fresh air, just at the place where it is most 
wanted, as no proper quantity of air can be obtained in banks 
of such limited area, situate out of the main air roads. This 
system of ventilation is economical in other ways, in addition 
to the increased safety afibrded to the miner, inasmuch as it 
dispenses altogether with the large outlay consequent upon 
the driving of long narrow roads, unprofitable in themselves 
as well as detrimental to the physical health of the workman ; 
it thus afibrds to the proprietor the quickest return for his 
invested capital. 
The ventilation under any system of pillars, is attended 
also with greater risk, on account of the large area of goaf 
shut up between these pillars, where the explosive gases 
accumulate, and are a constant source of danger in fiery 
mines. 
