Gold detector machine

The famous English scientist, Professor Foulbody, invented a machine which would tell you at once, without opening the wrapper of a bar of chocolate, whether or not there was a Golden Ticket hidden underneath it. The machine had a mechanical arm that shot out with tremendous force and grabbed hold of anything that had the slightest bit of gold inside it, and for a moment, it looked like the answer to everything. But unfortunately, while the Professor was showing off the machine to the public at the sweet counter of a large department store, the mechanical arm shot out and made a grab for the gold filling in the back tooth of a duchess who was standing near by. There was an ugly scene, and the machine was smashed by the crowd.

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Charlie and the Chocolate Factory, Chapter 6