VENTILATION OF MINES 



1065 



oud of the machine is represented open in the drawing, for the convenience of showing 

 the inlet valves E, and of explaining the internal construction. 



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A The upcast pit. 



B Hollow pistons, made of wrought iron. 



c Wrought-iron tanks, resting on two blocks of masonry, and on six iron pillars. 



D Beam work, resting on three blocks of masonry. 



E The valve work and framing, fastened to sixteen upright pieces of timber, 9 inches square. 



F Crank- wheel of steam-engine. 



o Piston-rods. 



In ventilating the very thick coal of Staffordshire, though there is much inflammable 

 gas, less care is needed than in the North-of England collieries, as the workings are 

 very roomy, and the air-courses of comparatively small extent. The air is conducted 

 down one shaft, carried along the main roads, and distributed into the sides of work. 

 A narrow gallery, termed ' the air-head,' is carried in the upper part of the coal, in the 

 rib walls, along one or more of the sides. Lateral openings, named ' spouts,' are led 

 from the air-head gallery into the side of the work; and the circulating stream, mixed 

 with the gas in the workings, enters by these spouts, and returns by the air-head to 

 the upcast .pit. 



The means adopted in the South Staffordshire coal-mines, which have seams vary- 



