Inventory no. 83344 - Former Display Label
English PELTIER ELECTROMETER
c.1850
Signed 'C. Becker, London'.
Two brass arms with small balls fixed to the central brass conductor penetrating the glass dome, are directly above paper scale divided into four quadrants. Indicator consists of crudely bent wire, ending in pith balls with central brass pivot and bar magnet, suspended on needle at centre of conductor and arms. Indicator probably not original. Bar magnet allows indicator to rest parallel to the earth's magnetic field, its pith balls in contact with brass arms. Charge given to central conductor is shared between arms and indicator causing its repulsion; the deflexion being measured on the scale.
This instrument, which is only roughly quantitative, was designed by J. C. A. Peltier (1785-1845) discoverer of the Peltier effect, for the study of atmospheric electricity. Thomas Milner had produced a similar electroscope in 1783, while R. H. Kohbrausch's sine-electrometer of 1853 was, in turn, a modification of Peltier's electrometer.
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Transferred from the Radcliffe Observatory