England · Late 18th century; practical forms widespread by c. 1780–1800
Bimetallic Compensation Balance
Partially verifiedTemperature compensation was essential to achieving chronometer-grade accuracy before the development of temperature-stable alloys such as Invar and Elinvar in the twentieth century.
A balance rim made of fused steel and brass (or similar dissimilar metals) curves inward or outward as temperature changes, altering the effective radius of the balance to counteract the tendency of a plain steel balance spring to run slow when warm.
Several makers contributed refinements; Earnshaw and Arnold are both credited with practical compensation-balance forms adopted for marine chronometers, and the type was progressively refined through the nineteenth century (including cut bimetallic balances to reduce middle-temperature error).
How to verify this yourself
Consult the National Maritime Museum's chronometer catalogue and The National Archives patent index for named claims; contested-priority details should be checked against Betts's scholarly work rather than watch-trade folklore.
Manufacturers known to have used it
- Marine chronometer makers generally, 19th century
- high-grade pocket watch manufacturers
Photographs
Photographs are illustrative examples of the type, not necessarily the exact object described. Verify details against the source file page.
Sources & references
- Betts, J., Arnold & Earnshaw: The Practicable Marine Chronometer (National Maritime Museum)
- Gould, R. T., The Marine Chronometer: Its History and Development
Where sources disagree, the disagreement is stated rather than resolved silently.