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Adjustable spark gap, early 19th century.

Adjustable spark gap, early 19th century.
4 0 c m
actual image size: 26cm x 32cm


This instrument consists esentially of two bras balls. The lower one is supported on an insulated blue glas pillar; the upper one can be held at the required height above it by a catch. The catch can be released to let the upper ball make contact with the lower one. Either ball could be earthed while the other was charged.

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