' Pr'oveedings of tes Polytechnic Association. 1011 



disinfectant as it destro,ys, or, at least, neutralizes contagious 

 infection. 



Gun Cotion. 



This material seems to be attracting public attention as an explo- 

 sive agent in mining operations. The principal objection to its use, 

 its liability to spontaneous decomposition, it is said, has been removed 

 by the use of a weak alkali, and it has been successfully employed in 

 the form of compressed charges. Messrs. Abel & Brown, of the 

 Royal Arsenal, Woolwich, the gentlemen who introduced these 

 improvements, have recently made a still more important discovery. 

 In experimenting with nitro-glycerine and gun cotton combined, it 

 occured to them to try the detonating fuse in exploding gun cotton 

 alone. The results showed that gun cotton exploded in this way has 

 even more destructive force than nitro-glycerine. A detailed account 

 of these experiments has not yet been made public ; but if the reports 

 which have reached us are correct, the discovery will be of great 

 importance to mining engineers. 



Dr. D. D. Parmelee. — I do not know that any explanation can 

 be given of the strange facts here announced. "We know that if a 

 powder magazine should explode, any other magazine existing in the 

 vicinity will be likely to explode too. If a little of any of the 

 fulminates be exploded, all the other packages of fulminates in the 

 neighborhood will explode. This is one of the circumstances which 

 render tlie use of fulminates so dangerous. 



Mr. J. Phin. — It is announced that the peculiar detonating or 

 fulminating property, which is described in the article read by the 

 chair, may be propagated even tlirough explosive material which is 

 not confined. Thus it is said that if a train of gun cotton be laid on 

 the floor, and one end of it be ignited by some sharply explosive 

 substance, the \vhole of the cotton will explode with great violence, 

 whereas if it be simply fired with a light or a flame it will burn 

 quietly. The action of various fulminates was then discussed, and 

 the well known pulvis fulminans, a preparation which has been 

 known for centuries, was adduced as an illustration of the subject on 

 hand. When simply fired it fizzles away, burning slowly and quietly ; 

 but if heated until it melts, so that the particles can all unite at the 

 same moment, it explodes with terrific violence, more resembling 

 the action of the metallic fulminates than the operation of a sub- 

 stance composed of materials resembling those which enter into the 

 composition of gunpowder. 



