438 



Mr. W. Galloway. 



[Mar. 23, 



was separated from the wooden gallery by certain sheets of paper 

 interposed between them in the form of a diaphragm. None but 

 sheets without visible flaws were employed for this purpose, and they 

 were inserted in the joint between the wooden gallery and the 

 explosion chamber in such a way that their edges projected into the 

 open air all round about. Seven minutes or so elapsed from the time 

 the flre-datnp was begun to be transferred into the explosion chamber 

 until its mixture with air was ignited. The largest quantity of fire- 

 damp employed in any one of the sixty-three experiments was 1*876, 

 or say, 2 cubic feet, and if even one-half of this quantity had escaped 

 there could have been no explosion, as the mixture remaining in the 

 explosion chamber would not have been inflammable. Admitting, 

 however, for the sake of argument, that, in every case, one cubic foot 

 of fire-damp passed through each sheet of paper in the diaphragm in 

 succession and found its way into the gallery, then its rate of escape 

 would be, say, one-seventh of a cubic foot per minute. But, during 

 the whole time the first forty-two experiments were in progress, there 

 was a current of fresh air amounting to upwards of 1,000 cubic feet 

 per minute constantly passing into the gallery immediately behind 

 the diaphragm and traversing it towards its open end. Therefore, 

 the greatest amount of fire-damp which the gallery could possibly have 

 contained at any moment before one of these explosions was effected, 

 even in the extreme case I have imagined, and with the further 

 supposition that all the doors were shut, was about one-fourteenth 

 part of a cubic foot, giving a mixture of one of gas to seven thousand 

 •of air, a proportion which is obviously far too small to be of the least 

 practical account. 



It appears necessary to give the foregoing explanation, inasmuch as, 

 in a report on some experiments made with dust from Seaham 

 colliery,* Professor Abel has made the following remarks regarding 

 the experiments conducted with the smaller apparatus described to 

 the Royal Society in 1879, and whatever applies to those experiments 

 in this respect, applies with equal force to the present ones, which are 

 nothing more than their continuation on a larger scale. At page 5, 

 Professor Abel says, — " The apparatus devised by Mr. Galloway for 

 the latter experiments was very ingenious, but it appears open to 

 question whether small quantities of fire-damp did not find their way 

 before the explosion from that part of the apparatus where the gas- 

 mixture was prepared and fired into the channel where the coal-dust 

 was raised, and into which the flame of the explosion was projected." 



The coal-dust employed in this series of experiments came from the 



* Report on the result of experiments made with the samples of dust collected at 

 Seaham Colliery in compliance with the request of the Secretary of State for the 

 Home Department, conveyed by a letter dated November 4, 1880. By F. A. Abel, 

 C.B., F.E.S., &c. 



