356 



Mr. W. Galloway on the Influence 



[Mar. 2, 



in mediately from the consideration that, without doubt, combustible 

 gases can supplant each other in certain equivalent proportions in mix- 

 tures which will just ignite at given temperatures, and that finely divided 

 combustible solids have probably the same property to some extent. 



Accordingly, when an opportunity occurred on the 3rd of July last, I 

 made experiments to test the correctness of these views. An apparatus 

 for testing safety-lamps in an explosive current had been erected for my 

 use at Llwynypia Colliery, in the Ehondda valley, through the kindness 

 of Mr. A. Hood, the Managing Director, and Mr. W. G. M c Murtrie, the 

 Manager of the Glamorgan Coal Company's Collieries ; and by having it 

 altered slightly, I was able to employ it also in making experiments with 

 coal-dust. This apparatus, of which fig. 1 is a vertical section, consists 



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of a horizontal wooden box or pipe, 18 ft. 9 in. long, by 12 in. deep, by 

 6 in. wide inside; it was connected with the covered top of the upcast 

 shaft by means of a vertical box of the same dimensions as itself in cross 

 section, and 4 feet long. A and F are sliding valves for regulating or 

 shutting off the air-current; B is a glass window, and b a small door on 

 the top of the box; D a wooden pipe 4 in. square inside, by 2 ft. long; 

 C a hopper for letting the coal-dust into the apparatus, and c an iron 

 pipe 2 inches in diameter, closed at the top by a wooden plug which 

 projected above the top of the hopper ; lastly, E is a malleable iron pipe, 

 which conducted firedamp from a closed space underground, in which 

 there is a strong blower. 



The valve at E having been closed, and that at A opened somewhat, a 

 current of air passed up through D into the apparatus, and, flowing past 

 B, escaped into the upcast, which is connected with an exhausting-fan. 

 A naked light was then placed inside the apparatus at B, opposite the 

 window ; the hopper was filled with coal-dust and the plug withdrawn 

 to a short distance above the top of c, and moved about gently. The 

 coal-dust falling through c into the upper end of D was winnowed by the 

 air-current; the larger particles fell down through D on to the ground 

 below, and the fine dust, with which the whole air-current was charged, 



