1068 



VENTILATION OF MINES 



does not contain above one-thirtieth of carburetted hydrogen, as indicated by its 

 effect upon the flame of a candle. The naked darts denote the portions of the mine 

 where the air, being charged to the firing-point, is led off towards D, the dumb furnace, 

 which communicates with the hot upcast shaft, out of reach of the flame, and thence 

 derives its power of draught. By suitable alterations in the stoppings (see the various 

 transverse lines, and the crosses) any portion of the workings may, by the agency of 

 the furnace, be laid out of, or brought within, the course of the vitiated current, at 

 the pleasure of the skilful mine-viewer ; so that, if he found it necessary, he could 

 confine, by proper arrangements of his furnace, all the vitiated currents to a mere gas- 

 pipe or drift, and direct it wholly through the dumb furnace. During a practice of 

 twenty years Mr. Buddie had not met with any accident in consequence of a defect in 

 the stoppings preventing the complete division of the air. The engineer has it thus 

 within his power to detach or insulate those portions of the mine in which there is a 

 great exudation of gas, from the rest ; and, indeed, he is continually making changes, 

 borrowing and lending currents, so to speak; sometimes laying one division or panel 

 upon the one air-course, and sometimes upon the other, just to suit the immediate 

 emergency. As soon as any district has ceased to be dangerous, by the exhaustion 

 of the gas-blowers, it is transferred from the foul to the pure air-course, where gun- 

 powder may be safely used, as also candles, instead of Davy's lamps, which give less 

 light. 



Till the cutting out of the pillars commences (see the right end of the diagram), 

 the ventilation of the several passages, boards, &c., may be kept perfect, supposing 



2084 



the working, extending no farther than a or b ; because, as long as there are pillars 

 standing, every passage may be converted into an air-conduit, for leading a current 

 of air in any direction, either to c, the burning, or D, the dumb furnace. But the 

 first pillar that is removed deranges the ventilation at that spot, and takes aw;iy 

 the means of carrying the air in the further recess towards c. In taking out the 

 pillars, the miners always work to windward, that is to say, against the stream of 

 air; so that whatever gas may be evolved shall be immediately carried off from the 

 people at work. When a range of pillars has been removed, as at d, e, f, no power 

 remains of dislodging the gas from the section of the mine beyond a, b; and as the 

 pillars are successively cut away to the left hand of the line ab, b, the size of the goaf, 

 or void, is increased. This vacuity, or goaf, is a true gas-holder, or reservoir, con- 

 tinually discharging itself at the points^, h, i, into the circulating current, to be carried 

 off by the gas-pipe drift at the dumb furnace, but not to be suffered ever to come in 

 contact with flame of any description. The next range of working is the line of 

 pillars to the left of a, b ; the coal having been entirely cleared out of the space to the 

 right, where the place of the pillars is marked by dotted lines. The roof in the 

 waste soon falls down, and gets fractured up to the next seam of coal, which, abound- 

 ing in gas, sends it down in large quantities, and keeps the goaf below continually 

 replenished. 



Description of the Ventilating Fan at the Abercarn Collieries. The late Mr. E. Eogers 

 having occasion to ventilate the workings in some extensive and very fiery coal-seams 

 won at Abercarn in South Wales, under circumstances where the furnace-ventilation 

 could not be applied, came to the conclusion that a plan of machine proposed for the 

 purpose by Mr. James Nasmyth would be the most suitable and effective. After con- 



