350 



Mr. Buddle's Narrative of the Explosion 



through the workings, as to be explosive. This objection to the furnace 

 is, however, greatly obviated by what I call the system of double ventilation. 

 The principle of this system is to supply the furnace with a current of air* 

 which is not exposed to the hazard of being contaminated by an admixture 

 of inflammable air. While the current of air, which is exposed to such 

 contamination, is delivered into the up-cast shaft by a separate out-let, so 

 as not to expose it to the risk of coming in contact with the flame of the 

 furnace. The annexed diagram explains the mode in which this is managed. 



a the upcast shaft, b the furnace, c the drift, by which the contaminated 

 air is carried off into the upcast shaft. 



The furnace b, always heats the air in the shaft a, sufficiently to draw 

 the current through the drift c. A furnace may be placed at d to be used 

 occasionally, as it frequently happens in practice that the furnaces have to 

 be worked alternately. The furnace d will draw the current of air as 

 well through the b furnace drift, as the furnace b, will draw the current through 

 the d furnace drift. Which ever furnace happens not to be at work is 

 called the dumb furnace, and the drift leading from it into the shaft is call- 

 ed the dumb furnace drift. This system admits of great modification, ac- 

 cording to circumstances, and the Bensham Seam, at Wall's End Colliery, 

 has, from its first opening in 1820, been ventilated according to its prin- 

 ciples. 



The enormous discharge of gas from this seam rendered it necessary to 

 have several distinct currents of air passing through the workings, some of 

 which supplied the burning furnaces, and the remainder were carried oif by 



