High Explosives

urer is, in fact, between two fires. The inspectors favour firm, elastic gelatins, in which the nitro-glycerin has been very completely taken up by the nitro-cotton. The miners, on the other hand, prefer gelatins which are soft and sensitive. A gelatin of plastic consistency, when freshly made, will generally show in a little while after storage a narrow line of free nitro-glycerin along the edge of the inner fold of the wrapper. There seems to be a strong capillary attraction along this line, probably due to the double fold, which tends to draw out of the jelly the free nitro-glycerin near it. If this line shows more than a trace of free nitro-glycerin, the inspector will condemn the stuff as exuding, and order it to be re- wrapped. If the nitro-glycerin extends into the folds, it may be destroyed. If, on the other hand, this line is absolutely absent, then under the conditions prevailing in the mines at the present time, the stuff is likely to be condemned by the practical users as being insensitive. If such a stuff is stored for many months before use, it is likely to develop the " Hake effect," and become very insensitive to even a proper detonator. The trouble arising from the inspector and the practical miner being so far apart in their ideas as to the right thing, has been aggravated in Australia by what I consider a false standard of sensitiveness. Unfortunately, it has become thefashion to use the minimum detonator for exploding gelatinous explosiv...