Jean and David Geiser, La Chaux-de-Fonds Perpetual movement clock Marble, brass, steel, enamel Height: 61 cm. Width: 41 cm. Depth: 26.5 cm. 1815 The illusion of perpetual motion is created by the movement of the twenty-four small brass weights on the rim of the large wheel, which makes one revolution a day. In reality, the clock is driven by a spring concealed in the wheel's hub. The clock movement, which is at the front, has a lever escapement with a balance and spring. The white enamel dial bears the inscription Et pourtant elle tourne (Nevertheless, it moves). A gear-train at the back, designed to regulate the movement of the large wheel, terminates with a shaft consisting of three conical runners resting on a polished mirror. Neuchâtel clockmakers in the late 18th and early 19th centuries carried out a lot of research into the principal of perpetual motion. Samuel Roy, Phinée Perret and especially Jean-David Maillardet made clocks for both the general public and scientists that appeared, at first, to have solved the problem. Jean and David Geiser, a father and son team of clockmakers at Les Eplatures near La Chaux-de-Fonds, made the clock illustrated here in 1815. History: 1991 (purchased). Bibliography: Chapuis, 1931, pp. 237-240 Tardy, 1974, p. 492, illus. Roberts, 1989, p. 115, illus. Ineichen sale, Zurich, 1990, n° 189, illus. Antiquorum sale, Genève, 1984, n° 95, illus. Cardinal, 1993, p. 16, illus. Chronométrophilia, 1993, n° 35, pp. 12-26, illus.