360 Mr. W. Galloway on the Influence [Mar. 2, 



represents the new arrangement. The same wooden box was employed ; 

 but instead of connecting it to the top of the upcast, a small blowing- 

 fan (A) driven by a steam-turbine was joined to it at one end, and the 

 other end was left open. B and D are windows ; C the hopper for coal- 

 dust; and E one of two sluice-valves, which can be pushed into the box 

 from each side until they meet in the middle, when they stop the air- 

 current coming from the fan. 



The fan draws the air into two chambers, one above and the other 

 below the blades ; from these chambers the air passes into the fan itself, 

 downwards and upwards through central openings, and is expelled into 

 the apparatus through a tangential pipe. 



The firedamp-pipe passes through one of the air-holes into the lower 

 chamber, and, being turned up at the end, terminates close to the blades. 



The whole of the firedamp coming from the blower is allowed to pass 

 into the fan; and as there is always an inward draught through the 

 air-inlets, the whole of it passes into the apparatus thoroughly mixed 

 with air. 



The qualitative experiment with this apparatus is made in the follow- 

 ing way: — The fan having been set in motion, a current of air and fire- 

 damp traverses the apparatus in the direction of the arrow. A safety- 

 lamp is then placed in the box opposite the window (B), and the velo- 

 city of the current is increased by opening the valves at E until the 

 flame of the lamp gives no indication of the presence of the firedamp. 

 After this the safety-lamp is removed and two naked lights substituted, 

 one opposite each window; and coal-dust is supplied through the hopper. 

 As soon as the cloud of coal-dust reaches the flame at D, it takes fire, 

 and either explodes backwards against the current, or fills the box with 

 a red flame from D to the end, according to the amount of firedamp in 

 the mixture. Meanwhile the lamp at B continues to burn exactly as 

 before, showing -no indication of the presence of the firedamp. This 

 experiment is quite conclusive. 



The quantitative experiment is slightly different. A safety-lamp is 

 placed at B, and the valves at E are closed very gradually until the cur- 

 rent becomes explosive; the velocity is then measured at D by means of 

 a small anemometer, observed through the window. After this the 

 valves are opened to any desired extent; the velocity of the current is 

 again measured; the anemometer is removed, and a naked light sub- 

 stituted for it at D, and coal-dust is admitted at 0. 



On the 16th of December I found that the current of air and firedamp 

 alone was just explosive when its velocity was 155 feet per minute; and 

 two other observations, made during the intervals between the experi- 

 ments with coal-dust, gave respectively 156 and 153 feet. Again, on the 

 5th of January it became explosive at 150 feet per minute. On the 

 former occasion the velocity was increased to 296, 331, 337, 440, 523, 

 and 543 feet per minute, and on the latter to 714, 808, 900, and 1060. 



