BLASTING

method of shattering large ma es of solid matter, such as rock, explosive compounds; used chiefly in quarrying, mining, engineering, and road railroad cutting, and for removing obstructions to navigation, such as reefs. Before the invention of gunpowder the only way rock could be quarried or removed was by chisel or wedge and hammer, or sometimes by ‘fire-setting,’ which consisted of building a fire on the rock then pouring on water, which caused the rock to crack and splinter. When large, regular blocks of stone are required, the wedge is still used, as the action of explosives generally shatters rock into irregular pieces. Up to 1864 gunpowder was the explosive compound generally used, but that year nitro-glycerine was applied b. by Alfred Nobel, who in 180/ invented dynamite. This name is now generally applied to any compound of highly explosive character. Other explosives are nitro-cotton and guncotton, porous substances which have absorbed a quantity of dynamite. Dynamite is seldom used in its free state, owing to its great tendency to explode accidentally. Litho-fracteur is a form of gun-cotton, whilst a combination of nitrate of barium and gun-cotton forms tonite. Gelatine or b. jelly is a solution gun-cotton in nitro-glycerine in a jelly-like form, and is of violent explosive force. Many other explosives have been invented, but the use of the majority is forbidden.