Gluck thought no more about it at the time. He merely re-wired his vat and went on electroplating. But afterwards, in prison, he remembered the incident, and like a flash there came into his mind the full significance of it. He saw in it the silent, secret weapon with which to revenge himself on the world. His great discovery, which died with him, was control over the direction and scope of the electric discharge. At the time, this was the unsolved problem of wireless telegraphy—as it still is to-day—but Emil Gluck, in his prison cell, mastered it. And, when he was released, he applied it. It was fairly simple, given the directing power that was his, to introduce a spark into the powder-magazines of a fort, a battleship, or a revolver. And not alone could he thus explode powder at
