Atmos II self-winding clock by Jaeger-LeCoultre, 1930s
Image number: 1939-259
This clock has a bellows filled with ethyl chloride gas which expands and contracts with changes of temperature and atmospheric pressure. These movements wind a large spring by a ratchet mechanism, so the clock never needs to be wound.
Source: De Trevars Ltd
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- Science Museum/Science & Society Picture Library
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