A French nickel plated atmos clock, J.L. Reutter, circa 1933
9-cm enamel dial with Roman numerals signed ATMOS pendule perpetuelle and below Brevets J.L. Reutter, blued steel Breguet hands, movement with a large horizontal balance slowly turning, driven by a spring wound by a mechanism turning by temperature changes numbered 2234, nickel plated brass case with glass panels to all sides, raised on a canted base.
This almost modern looking clock isn’t only fascinating because of its fine clear design. Besides this the clock holds a very interesting movement. The Swiss engineer Jean-Léon Reutter invented the atmos clock in 1928. It took him quite a while and effort to combine the torsion pendulum from the year-going anniversary clocks with his temperature sensitive device. This device consisting of a drum holding mercury in glass tube which causes the drum to turn when the mercury expands or retracts. This motion is used to wind a small spring which drives the movement. Because the clocks doesn’t need any winding because of this mechanism he called the clock a ‘pendule perpetuelle’ (perpetual mantel clock).