BLASTING

the technical term for splitting breaking up any object by means of gunpowder. The operation, which is of extensive use in quarrying, mining, and generally in all branches of engineering, is performed by boring a hole in the subetakoe exploded, by means of an iron rod, called a jumper, filling it with gunpowder, and igniting it by of a match, burning so slowly as to allow the employed to remove to a sufficient distance the explosion takes place. At one time it was posed that the force of the explosion depended tiim packing of the gunpowder in the hole by of small chips of stone, sand, . In this operation the gunpowder was sometimes accidentally ignited, and frightful accidents took place. It has since ascertained that loose sand is as effectual as packing, which in consequence has been generally laid aside. One of the most important modem provements in blasting, is the firing of the chaige galvanism. This mode is more especially applicable to submarine blasting, and was first practised for purpose by General Pasley, in 1839. The only nece ary Ib to make an interruption in the conducting wire at the point where the explosion is to place. In pa ing the electric current, a spark duced at the interruption fires the charge. The being instantaneous the operator can fiie any number of charges simultaneously. Gun-cotton is often ployed in blasting, and nitro-glyoerine has also found to be a very powerful agent in such operations, but its use requires the utmost caution, as it liable to explode unexpectedly with most disastrous results. The same objection does not apply to mite (which see), a mixture of nitro-glycerine sand, which is quite as effective and peif ectiy le , except when ignited by a fuse.