1062 



VENTILATION OF MINES 



or become extinct for a little, the circulation will still go on, the air of the upcast pit 

 being rarefied by the heat remaining in the sides of the shaft. 



To prevent the annoyance to the onsetters at the bottom from the hot smoke, the 

 plan has been adopted, as shown in the wood-cut, Jig. 2072, where a represents the 

 lower part of the upcast shaft ; b, the furnace, built of brick, arched at top, with its 

 sides insulated from the solid mass of coal which surrounds it. Between the furnace 

 wall and the coal-beds a current of air constantly passes towards the shaft, in order 

 to prevent the coal catching fire. From the end of the furnace a gallery is cut in a 

 rising direction at c, which communicates with the shaft at d, about 7 or 8 fathoms 

 from the bottom of the pit. Thus the furnace and the furnace-keeper are completely 

 disjoined from the shaft ; and the pit-bottom is not only free from all incumbrances, 

 but remains comfortably cool. To obviate the inconveniences from the smoke to the 

 banksmen in landing the coals at the pit-mouth, the following plan has been contrived 

 for the Newcastle collieries. Fig. 2073 represents the mouth of the pit : a is the up- 

 cast shaft, provided with a furnace at bottom ; b, the downcast shaft, by which the 

 supply of atmospheric air descends; and d, the brattice carried above the pit-mouth. 

 A little way below the settle-boards, a gallery, c, is pushed, in communication with 

 the surface from the downcast shaft, over which a brick tube or chimney is built from 

 60 to 80 feet high, 7 or 8 feet diameter at bottom, and 4 or 5 feet diameter at top. 

 On the top of this chimney a deal funnel is suspended horizontally on a pivot, like a 

 turn-cap. The vaney, made also of deal, keeps the mouth of the funnel always in the 

 same direction with the wind. The same mechanism is mounted at the upcast shaft 

 a, only here the funnel is made to present its mouth in the wind's eye. It is obvious 



2072 



2074 



from the figure, that a high wind will rather aid than check the ventilation by this 

 plan. 



The principle of ventilation being established, the next object in opening up a 

 colliery, and in driving galleries, is the double mine or double headways course ; on 

 the simple but ingenious distribution of which, the circulation of air depends at tho 

 commencement of the excavations. 



The double headways course is represented in fig. 2074, where a is the one heading 

 or gallery, and b the other ; the former being immediately connected with the upcast 

 side of the pit c, and the latter with the downcast side of the pit d. The pit itself is 

 made completely air-tight by its division of deals from top to bottom, called ' the brat- 

 tice wall ' ; so that no air can pass through the brattice from d to c, and the intercourse 

 betwixt the two currents of air is completely intercepted by a stopping betwixt the pit- 

 bottom and the end of the first pillar of coal ; the pillars or walls of coal, marked e, 

 are called ' stenting walls ; ' and the openings betwixt them, ' walls ' or ' thirlings/ Tho 

 arrows show the direction of the air. The headings a and b are generally made about 

 9 feet wide, the stenting-walls 6 or 8 yards thick, and are holed or thirled at such a 

 distance as may be most suitable for the state of the air. The thirlings are 5 feet wide. 



When the headings are set off from the pit-bottom, an aperture is left in the 

 brattice at the end of the pillar next the pit, through which the circulation betwixt 

 the upcast and downcast pits is carried on ; but whenever the workmen cut through 

 the first thirling No. 1, the aperture in the brattice at the pit-bottom is shut ; in con- 

 sequence of which the air is immediately drawn by the power of the upcast shaft 

 through that thirling as represented by the dotted arrow. Thus a direct stream of 

 fresh air is obviously brought close to the forehead where the mines are at work. 

 The two headings a and b are then advanced, and as soon as the thirling No. 2 is cut 

 through, a wall of brick and mortar, 4 inches thick, is built across the thirling 

 No. 1. This wall is termed ' a stopping; ' and being air-tight, it forces the whole circu- 

 lation through the thirling No. 2. In this manner tho air is always led forward, and 

 caused to circulate always by the last-made thirling next the forehead ; care being had, 

 that whenever a new thirling is made, the last thirling through which tho air was 

 circulated be secured with an air-tight stopping. In the woodcut, the stoppings aro 

 placed in the thirlings numbered 1, 2, 3, 4, 5, 6, and of consequence the whole cir- 

 culation passes through the thirling No. 7, which lies nearest the foreheads of the 



