1898 - Coalmininghistorypa.org

106 REPORT OF THE BUREAU OF MINES. Off. Doc,house; if it does not touch the powder, nothing happens, but itspresence is at all times dangerous.The most prolific cause ol mine fires at present is the igniting ofstrong gas feeders by blasting, and by the careless use of nakedlight in gaseous gangways, and in the vicinity of gas feeders, andgas accumulations. The gas feeders are so numerous at manyplaces that when one is ignited all the others ignite and the wholepassage becomes a sheet of flame which is exceedingly difticult to extinguish.They are liable to be ignited by the sc^uib used in firingblasts. The commonly used black powder ignites the feeders withnearly every blast. The so-called flameless powder, and the highexplosives generally- ignite the feeders ifused in improjier temperature,but allthe high explosives ignite the gas much less frequentlythan the black powder and for that reason are much preferable forblasting in extremely gaseous ijlaces.All nitroglycerine compounds freeze at about 42 degrees Fahrenheitand explode at a temperature of oOO degrees Fahrenheit.Whenignited in the open air unconfined, it burns without explosion; itlosesignites gas feeders when charged in a frozen condition, and itmuch of its efficiency and isi difGcult to explode with a cap. FrozenThecartridges should be thawed before being charged for blasting.following rules are furnished by the manufacturers for thawing nitroglycerinecompounds:''When the cartridges are frozen, do not expose to a direct heat,but thaw by one of the following methods:''First. Place the number of cartridges needed for the shift orday's work on shelves in a room heated by steam pipes (not live steam)ror a stove, lamp or fire."Taking cartridges out as holes are ready for loading. If a smallhouse is built for this purpose, bank it around with earth, or preferablyfresh nmnure."Second. Use two water tight kettles, one smaller than the other;put (he cartridges in the smaller kettle and place the same in thehuge kettle, filling space between kettles with hot water at 130 to140 degrees Fahrenheit or so that the hand can be held in it. Tok(;e]) water warm do not try to heat it in the kettle, but add freshwarm water. Cover kettles to retain llie heat. Do not in thawingallow the temperature to get above 212 degrees Fahrenheit.''Third. AN'here llic nnuibcr of caiUidges to be thawed is small,they may be placed about the persou of the blaster until ready for use."Do not thaw cartridges by i»ulting them in hot water or by exposingthem 1o live steam, as this (iinfoil miately very common)method has an iiijiirious elVect on the powdvi-. Do not thaw cartridgesby holding them in the hand before a lire. Keep cartridges