Blasting

the process of removing obstructions by the use of explosives. Quarrymen save themselves labor by drilling holes and filling them partially with charges of powder. One end of a piece of fuse is placed in the powder and the hole is filled up to the surface with loose sand or with scraps of rock tamped down solid. The free end of the fuse is then fired and the quarryman retires to a safe position, which he is able to do before the fire reaches the powder. The sudden explosion throws off a mass of rock, doing work that would otherwise cost days of labor. In lieu of a fuse electric circuits may be employed. The ends of the wires are separated slightly; in leaping the gap the spark ignites the powder. A number of charges may be ignited at the same instant in this way, cracking off long strips of rock as neatly as though done with a saw. Nitro-glycerin and gun cotton are too dangerous, but dynamite or silicious earth, saturated with nitro-glycerin, may be used for the purpose. In 1843 three dynamite charges of 6,000 pounds each were fired simultaneously to blow up a portion of the Dover cliff required in the construction of a breakwater. Miners employ dynamite in loosening ore and coal, and in digging tunnels. Farmers put a cartridge of dynamite under a stump to throw it out of the ground. A dangerous reef known as Hell Gate, in the East River between New York City and Long Island, was removed by charging twenty tunnels with over twenty-five tons of dynamite and powder. Several million tons of rock that had long been a menace to shipping were thrown out in a single explosion. During the siege of Port Arthur by the Japanese immense blasts of dynamite were used that literally tore the faces off the mountains, and rendered expensive fortifications worthless. See Powder; Dynamite