VENTILATION OF MINES 



1063 



headings, a, b. By inspecting the figure, we observe that on this very simple plan a 

 stream of air may be circulated to any required distance, and in any direction, how- 

 over tortuous. Thus, for example, if while the double headways course a, b, is pushed 

 forward, other double headways courses are required to be carried on at the same 

 time on both sides of the first headway, the same general principles have only to be 

 attended to as shown in Jig. 2075, where a is the upcast and b the downcast shaft. 

 The air advances along the heading c, but cannot proceed farther in that direction 

 than the pillar d, being obstructed by the double doors at e. It therefore advances 

 in the direction of the arrows to the foreheads at f, and passing through the last 

 thirling made there, returns to the opposite side of the double doors, ascends now the 

 heading g to the foreheads at h, passes through the last-made thirling at that point, 

 and descends, in the heading i, till it is interrupted by the double doors at k. The 

 aerial current now moves along the heading /, to the foreheads at m, returns by the 

 last-made thirling there, along the heading n, and finally goes down the heading o, 

 and mounts by the upcast shaft a, carrying with it all the noxious gases which it 

 encountered during its circuitous joiirney. This woodcut is a faithful representation 

 of the system by which collieries of the greatest extent are worked and ventilated. 

 In some of these the air courses are from 30 to 40 miles long. Thus the air con- 

 ducted by the medium of a shaft divided 2075 

 by a brattice-wall only a few inches thick, 

 after descending in the downcast in one 

 compartment of the pit at 6 o'clock in the 

 morning, must thence travel through a 

 circuit of nearly 30 miles, and cannot arrive |p 

 at its reascending compartment on the other 

 side of the brattice, or pit partition, till 6 

 o'clock in the evening, supposing it to move ^ 

 all the time at the rate of 2 miles per |! 

 hour. Hence we see that the primum mobile 

 of this mighty circulation, the furnace, must 

 be carefully looked after, since its irregu- 

 larities may affect the comfort, or even the 

 existence of hundreds of miners spread over 

 these vast subterraneous labyrinths. On the 

 principles just laid down, it appears, that if 

 any number of boards be set off from any 

 side of these galleries, either in a level, dip, 

 or rise direction, the circulation of air may be advanced to each forehead by an ingoing 

 and returning current. 



Yet while the circulation of fresh air is thus advanced to the last-made thirling next 

 the foreheads /, h, and m, Jig. 2075, and moves through the thirling which is nearest 

 to the face of every board and room, the emission of fire-damp is frequently so 

 abundant from the coaly strata, that the miners dare not proceed forwards more than a 

 few feet from that aerial circulation, without hazard of being burned by the combustion 

 of the gas at their candles. To guard against this accident, temporary shifting 

 brattices are employed. These are formed of deal, aboiit of an inch thick, 

 3 or 4 feet broad, and 10 feet long; and are furnished with cross-bars for binding the 

 deals together, and a few finger-loops cut through them, for lifting them more ex- 

 peditiously, in order to place them in a proper position. 



The mode of applying these temporary brattices, or deal partitions, is shown in the 

 accompanying figure (2076), which shows how the air circulates freely through the 

 thirling d, d, before the brattices are placed. At b and c, we see two 

 heading boards or rooms, which are so full of inflammable air as to bo 

 imworkable. Props are now erected near the upper end of the pillar e, 

 betwixt the roof and pavement, about 2 feet clear of the sides of the 

 next pillar, leaving room for the miner to pass along between the pillar 

 side and the brattice. The brattices are then fastened with nails to the 

 props, the lower edge of the under brattice resting on the pavement, 

 while the upper edge of the upper is in contact with the roof. By this 

 means any variation of the height in the bed of coal is compensated by 

 the overlap of the brattice boards ; and as these are advanced, shift- 

 ing brattices are laid close to and alongside of the first set. The miner 

 next sets up additional props in the same parallel line with the former, and slides 

 the brattices forwards to make the air circulate close to the forehead where he is 

 working ; and he regulates the distance betwixt the brattice and the forehead by 

 the disengagement of fire-damp and the velocity of the aerial circulation. The props 

 are shown at d d, and the brattices at //. By this arrangement the air is pre- 



2076 



