1882.J On the Influence of Coal-dust in Colliery Explosions. 437 



I regret that, up to the present, I have been unable to procure a 

 record of any other actinometrical observations that would serve to* 

 test the correctness of these results. 



II. " On the Influence of Coal-dust in Colliery Explosions. No. 

 IV." By W. Galloway. Communicated by Robert EL 

 SCOTT, F.R.S. Received December 29, 1881. 



In the concluding pages of No. Ill paper, now in the hands of the 

 Royal Society, I described an apparatus the essential parts of which 

 consist of a wooden gallery about 126 feet long by 2 feet square, and a 

 sheet iron cylinder about 6 feet long by 2 feet in diameter ; and, at 

 the same time, I gave a short general account of the experiments 

 that had been made with it up to that date, intending to resume the 

 subject on some future occasion. It will be remembered that the 

 experiment was made by mixing together and igniting a small 

 quantity of fire- damp and air in the sheet iron cylinder called the- 

 "explosion chamber"; that the resulting explosion burst through a 

 paper diaphragm which separated the explosion chamber from the 

 wooden gallery and created an air- wave ; that the air- wave in passing- 

 through the gallery swept up coal-dust from the floor and from certain 

 shelves placed at given points in it ; and, lastly, that the flame of the 

 original fire-damp explosion traversed the cloud of coal-dust and air 

 to a greater or less distance from the origin. 



During the warm dry weather prevailing between the 14th and 

 21st of July last, I made sixty-three further experiments, which for 

 convenience may be separated into the three following well-defined 

 groups. 



I. Fifteen to ascertain how far the flame of the mixture of fire- 

 damp and air contained in the explosion chamber would extend along 

 the wooden gallery in the absence of every trace of coal-dust. 



II. Thirty-eight to ascertain how far the flame produced in the- 

 same manner and under the same conditions as in the preceding case 

 would extend into a cloud of coal-dust and pure air, created by the 

 action of the air- wave in its passage through the wooden gallery. 



III. Ten to ascertain the effects due to the explosion of small heaps^ 

 of blasting powder placed at given points in the wooden gallery, all 

 the other conditions being exactly the same as in the last case. 



In each experiment the fire-damp was carefully and accurately- 

 measured by water displacement in a special cylinder called the 

 measuring cylinder in the two preceding papers. No fire-damp could 

 enter any part of the apparatus without first passing through the 

 measuring cylinder, and being thence transferred into the explosion 

 chamber. As has been previously stated, also the explosion chamber 



