1882. j on Some of the Dangerous Properties of Dusts. 97 



portion of air. The coal dust was placed ou the floor of the gallery 

 and upon certain shelves fixed in it. It appeared open to question 

 whether, with the employment of this apparatus, there was not a 

 possibility of very small quantities of fire-damp penetrating, before 

 the explosion, into the gallery from the explosive chamber, through 

 the closing arrangement above alluded to, and whether the results 

 obtained in the gallery might, consequently, be accepted as produced 

 solely by the effect of the concussion produced and flame promoted 

 by the gas explosion in the separate chamber. 



In a paper just communicated to the Royal Society, Mr, Galloway 

 argues that any amount of gas which may thus escape into the gallery 

 must be altogether insignificant as regards any possible influence 

 upon the results obtained. 



The conclusion now arrived at by Mr. Galloway, as the result of 

 continued experiments with this apparatus, of which he has just given 

 a further account, and of his examination into the eifects produced by 

 the Penygraig explosion in December 1880, and the Eisca and 

 Seaham explosions of that year, is confirmatory of that published 

 by him last year, namely, that the very decided view which he first 

 held, " that a mixture of air and coal-dust is not inflammable at 

 ordinary pressure and temperature without the presence of a small 

 projDortion of fire-damj)," has not been borne out by his further 

 experiments, as he considers that he has now shown " conclusively 

 that fire-damp is altogether unnecessary for the propagation of flame 

 with explosive effects by a mixture of coal dust and air," when the 

 scale on which the experiments are made is large enough, and when 

 the fineness and dryness of the dust are " unquestionable." 



This conclusion coincides in the main with that arrived at in 1878, 

 as the result of experiments by Professor Freire Marreco, conducted 

 in connection with the North of England Institute of Mining and 

 Mechanical Engineers, which Society, as well as the Chesterfield and 

 Derbyshire Institute of Engineers, has laboured very usefully in this 

 direction cotemporaneously with Mr. Galloway. The most recent 

 conclusions of the latter in respect to coal dust were in fact fore- 

 stalled by those which the late lamented Professor Marreco in asso- 

 ciation with Mr. P. D. Morison communicated to the first-named 

 Institute in November 1878, and which were published in its Trans- 

 actions of that date. 



Messrs. Marreco and Morison's experiments were carried out in 

 galleries or long boxes, representing mine workings, though on a 

 smaller scale than Mr. Galloway's later apparatus, and constructed 

 somewhat difierently in their details. The apparatus used by them 

 at Harton Colliery (and with which experiments have since been 

 continued by Messrs. Lindsay Wood and G. May), was in fact a 

 double gallery, so arranged that the air current which passed into 

 one gallery made its exit at the end of the second, alongside the 

 point of its first entrance. The mode of proceeding was to fire suc- 

 cessively two powder shots, in different positions in the gallery box, 



Vol. X. (No. 75.) h 



