English: Cavallo's multiplier: a 1795 device to amplify a small electric charge so that it could be detected by the electroscopes of the day.

The charge to be multiplied was applied to a metal plate A, which was supported on an insulating glass post. A moveable insulated metal plate B was brought close to A (though not permitted to touch it), and then grounded via a conducting wire F making contact with an earthed pin E. The charge on A caused charge separation on B due to electrostatic induction. Plate B was then moved away with the handle G, breaking its earth connection with E. Since B was insulated, it acquired and retained a small charge opposite in sign to the charge on A. Plate B was then brought into electrical contact with the third metal plate C, which was insulated. Since both B and C were conducting, B would transfer a portion of its charge to C. To maximise the transferred charge, C was placed in close proximity to a final metal plate D, which was earthed.

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