Compressed Air Work And Diving 1909

102 COMPRESSED AIR WORK. this method with favour, on the ground that during tamp- in«' the detonator mipht come out and o'et into contact O O o with the rock. The cartrid<»e so charged is commonly known as an O O J “ exploder,” and “detonates” all the other cartridges in the same hole. When Alling the borehole a wooden tamping rod shoulcl be used, and with this the cartridges should be tightly presseel home as put in. The borehole should be made only just large enough to take the cartridges, as if too large a good deal of the force of the explosion will be lost. The exploder is generally put in last, or last but one, and very little force must be used with the tamping rod after it has been inserted. Finally the hole shoulcl be filled with clay, clry sand, or paper. Water is also suitable if the hole is in a downwarcl clirection. It filis up all voids, and causes the force of the explosion to be immecliately felt by the rock without any previous loss of power in expansion. Below 45 degs. Fahr. nitro-glycerine is liablc to become congealed, and when in this condition the ex- plosive must not be used until thawed. The best and safest way to do this is to use a warming pan specially constructecl for the purpose, and which will be supplied by the makers. These pans have a double shell, and the space between is filled with hot water. In the States the practice is sometimes adopted of submerging the cartridges in a bueket of hot water. This custom appears a little dangerous, as there would seem some chance of the nitro-glycerine exuding and getting on to the operators hands or clothes. This method coulcl not be used with dynamite, from which the nitro-glycerine will exude in water. It may be as well to point out here that there are some very strict regulations in this