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Inventory no. 83947 - Former Display Label

c. 1860

Signed "Ruhmkorff, Rue des Orfevres 6, Paris"
Brass base, 3 levelling screws, silvered scale divided in degrees with centre zero; astatic needle suspended by fibre, and coil in rectangular ivory frame. Coil and needle arrangement rotated by worm-gearing beneath base. Overall height 23cm.

Astatic needle arrangement (in which two parallel magnetized needles of equal strength, have poles in opposite direction), is not influenced by earth's magnetic field. Designed by Nobili (1825), and later further improved by Du Bois Raymond and Kelvin, amongst others. The instrument maker Ruhmkorff is well-known for his improved version of the induction coil.


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