Through a delightfully complicated and beautiful system involving two inversely-polarized sterling engines, a complex system of gears and discs, and a backup battery, the Sterling Engine Clock tells time forever while you stare at it, contemplating the mysteries of the universe.-- Spacecoyote, Nov 17 2007 Beverly Clock http://en.wikipedia.../wiki/Beverly_ClockDriven by variations in atmospheric pressure and by daily temperature variations, running since 1864. [Spacecoyote, Mar 16 2011] Far more fuel-efficient than my internal combustion engine clock. [+]-- shapu, Nov 18 2007 random, halfbakery