Explosives are not only useless but dangerous unless the exact time and place they explode can be precisely controlled. Explosives would not have had the influence they have had on world history if two other devices had not been invented. The first device was invented in 1831 by William Bickford, an Englishman. He enclosed gunpowder in a tight fabric wrapping to create the first safety fuse. Lit at one end, the small amount of gunpowder in the core of the fuse burned slowly along the length of the cord that surrounded it. When the thin, burning core of gunpowder reached the end of the cord, it detonated whatever stockpile of explosive was attached. Only when the burning gunpowder in the fuse reached the stockpile did an explosion happen. This enabled users of explosives to set off explosions from a safe distance at a fairly predictable time.
In 1865, Nobel invented the blasting cap, a device that increased the ease and safety of handling nitroglycerin. Blasting caps, or detonators, send a shock wave into high explosives causing them to explode. It is itself a low explosive that is easily ignited. Detonators are ignited by primers. Primers burst into flame when heated by a burning fuse or electrical wire, or when mechanically shocked. A blasting cap may contain both a primer and a detonator, or just a primer. Another technique for setting off explosives is to send an electric charge into them, a technique first used before 1900. All these control devices helped increase the use of explosives for peaceful purposes.
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