Jaeger-LeCoultre 'Atmos II' self-winding clock, c 1939.
© Science Museum / Science & Society Picture Library
Detail of mechanism. The 'Atmos' is a spring-driven table clock which is kept wound entirely by changes in atmospheric temperature and presure. A set of gas-filled metal bellows, which are connected through a chain and pulley to the mainspring, move in and out with such changes. A change in temperature of just plus or minus one degree will keep the clock wound for 48 hours. It is regulated by a torsional (twisting) pendulum, which beats twice per minute. Over half a million Atmos clocks have been manufactured since coming on to the market in 1936. Manufactured by De Trevars Ltd of London, England.