1879.] Influence of Coal-dust in Colliery Explosions. 415 



Referring to fig. 1, which represents the whole arrangement, e, f, g, h 

 is the chimney of a Guibal fan, through which all the air from the 



Fig. 1. 



workings, amounting to about 80,000 cubic feet per minute, is ejected 

 into the atmosphere, a, b, c, d is a bent pipe partly made up of square 

 wooden boxes, partly of round sheet iron pipes ; at the end, a, it over- 

 hangs, and partly dips into, the chimney of the fan ; and at the other 

 end the part c, d, runs along the surface of the ground. Jc is a branch 

 of the same area in cross section as the other wooden parts of the 

 apparatus ; it is covered on the top, but is provided with a hopper I, 

 having a wooden plug m i through which coal-dust can be introduced, 

 v is a valve by means of which the velocity of the current can be 

 regulated, and n is a door. 



When the regulating valve is full open a strong current of return 

 air, amounting to 1,251 cubic feet per minute, passes through the appa- 

 ratus, and makes its escape at d. This air is not only saturated with 



