Why not utilise this propensity? Mark the case “watches,” “jewellery,” or “bullion,” cause it to be surrounded with a certain amount of mystery and precaution enough to engender suspicion; and leave the rest to the chisel and drill of the would-be thief. But this, though clever, was too uncertain. Another idea which occurred to him was to have a wooden case only, but a strong one, and to confine in a small hole prepared for the purpose one of the boring insects, which in a certain time would be sure to eat its way through and leave an aperture. This, too, was more ingenious than practicable. He was delayed for a time. Accident solved the difficulty. Passing through the streets, he was stopped by a crowd which had collected around a quack doctor. “See,” cried the vendor of patent vegetable pills, “here is the horrid stuff the allopathists, the doctors and physicians sell to you at high prices. Here is a common drug used by them in this phial. I will pour some of the liquid upon the hard stone pavement—just see how it acts upon the granite, and then guess how your wretched stomachs must be abused.” He poured it on the stone—the crowd pressed forward, and saw it eat a hole. “Aquafortis,” thought Theodore, and the idea was his—aquafortis was the agent he wanted. He passed on, and left the crowd thoroughly convinced of the tricks played by the medical faculty, and purchasing largely of the vegetable pills. Theodore had found a substance which would eat through his iron and wood cases, and leave an aperture—a substance, too, whose action was equal, and could be regulated to a sufficiently accurate extent. Upon reflection, however, and after making several experiments, he did not employ ordinary aquafortis, but another acid equally powerful, and which was still more regular in its action. He tried the experiment time after time, till at last he obtained the proper strength, and fixed the requisite amount of acid to eat through a given thickness of iron and wood in a certain time. He repeated the experiment till he was absolutely certain of the result. The plan had now grown delightfully clear and well-defined—the infernal machine became of the simplest construction. All that had to be done was to place the acid in the case confined in a small and very thin copper vessel (lined with an enamel to resist it), which was to be screwed to one side of the case, then pump the gas in, hermetically seal it, heave the whole thing on board the steamer, and leave it to work its way. Delightfully simple!