In 1832, the year of Michael Faraday's discovery that a changing magneticfield produces an electric field, a young French engineer patented a new and more efficient waterwheel.
The technique generates a magneticfield on a small part of the skull which creates weak electric currents in the brain.
这种手段在一小块头骨上形成一个磁场，既而在大脑中产生微弱的感应电流。
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He also realised that varying the strength of an electricfield would generate a changing magneticfield, even in empty space with no moving electric charges to speak of.