At Scotland Yard
The experts to whom the curious device found by the electrician in the little cellar had been sent duly made their report. In their opinion, the butt was all that remained of an ingenious poison-bomb. The original machine consisted of a socket made to fit into an ordinary lamp-holder, but the place of the filament had been taken by a piece of fine wire, round which had been wrapped a thread of guncotton. Attached to the socket, and in contact with the guncotton, had been a sealed celluloid bulb containing pure prussic acid.
The action of such a bomb would be perfectly simple. It had only to be placed in a lamp-holder, and the switch turned on. The current would heat the fine wire, and so ignite the strand of guncotton. This in turn would set fire to the celluloid bulb, and its contents would be released in the form of vapour. Although some of this vapour would become ignited, enough would be available to permeate the atmosphere of a room far larger than the small cellar. And, of course, the inhalation of the vapour would rapidly produce death.