1882.] on Some of the Dangerous Properties of Dusts. ' 105 



curre. commeDcing at 18 feet from the end, and 2 feet 6 inches 

 apart, in the opposite wall there were fonr, commencing at the sama 

 distance and 5 feet apart : oyer the wall at the blocked end of the 

 gallery there was an opening into the outer air. and a considerable 

 current of air passed through it along the gallery to the curved 

 end, which led into a large narrow gallery at right angles to this wide 

 one, and having large chambers opening into it. 



In some preliminary experiments, an iron tube was let into the 

 face of the wall at the blocked end of the gallery, so as to represent 

 a strong blast hole, and this was charged with 1-^ lb. of powder, 

 untamped in some experiments and tamped in others, some pieces of 

 guncotton were suspended from the roof of the gallery at a distance 

 of 28 feet and farther along, and observers were stationed outside 

 the gallery opposite the several loop-holes. But, while the pieces 

 of guncotton were not inflamed, there were conflicting opinions 

 concerning the distances at which flame was seen, probably caused 

 by the general illumination of the gallery by the flash of the 

 explosion. It was, moreover, found that the iron tubes containing 

 the charges were more or less considerably torn, so that portions of 

 the exploding charge escaped laterally. The following method of 

 experimenting was eventually adopted. Charges of IJ lb. and 2 lb. 

 of powder, untamped and tamped, were fired from a small roughly 

 bored out gun-block, the bore of which was 1 foot 9 inches long and 

 2f inches in diameter ; the gun was raised so as to project the flame 

 right along; the sallerv at about its centre. A light woodwork frame. 

 5 feet square, was fitted with thirty-six cross wires 1 foot apart, so as 

 to furnish thirty-six points of intersection ; to each of these points a 

 small tuft of guncotton was attached, and the target thus fitted was 

 fixed verticallv so as to face the charge, in the centre of which was 

 fixed an electric fuze. In this way small charges of grmcotton were 

 distributed uniformly over all parts of the target, which filled a great 

 part of the section of the galleiy. The distance of the target from 

 the charge being gradually increased in successive experiments to 

 20 feet, it was found that with the employment of IJ lb. and 2 lb. 

 charges, imtamped, in three instances cut of ten experiments only one, 

 or at most two of the tufts of guncotton were inflamed, this being 

 apparently the extreme distance to which flame, or matter sufficiently 

 hot to inflame guncotton, was projected. At a distance of 19 feet, 

 with 1 J lb. charges, two out of three shots did not inflame any of the 

 gimcotton tufts. With IJ lb. charges fiiToly tamped, one tuft only 

 of the thirty-six was fired, in two experiments, at a distance of 20 feet, 

 while in three others no guncotton was inflamed. 



It appears from these results that in a gallery or mine-working oi 

 an area not very dissimilar to that in which the accidents just referred 

 to occurred, the flame or heated gases from 1^ lb. and 2 lb. charges, 

 fired tmder conditions favourable to the production of the maximum 

 flame, and its complete projection in the direction of the discharge, only 

 reaches occasionally, and to a very limited extent, io a distance of 



