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The planetary clock

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Lorenzo della Volpaia

Lorenzo della Volpaia founded a family dynasty of artist-engineers who worked in Florence and Venice until the late sixteenth century. The Della Volpaias were highly regarded clockmakers and manufacturers of scientific instruments. Lorenzo had contacts with Leonardo and mentions some of his inventions, like the water meter built for Bernardo Rucellai.

Planetary clocks

Lorenzo's most noteworthy project was the planetary clock, which he built in two different versions. The second, completed in 1510, was installed in the Sala dei Gigli of Florence's Palazzo Vecchio. The device had already vanished by the late sixteenth century.

The main purpose of planetary clocks was not to keep time but to show the position of the heavenly bodies relative to the Earth, so that astrological influences could be calculated with precision. Planetary-clock construction required a thorough knowledge of astronomy, highly accurate computations, and proficiency in mechanical fabrication.

The planetary clock

The Della Volpaias' notebooks contain the information needed to reconstruct Lorenzo's clock?a project undertaken in 1994 at the Istituto e Museo di Storia della Scienza in Florence.

The clock displays a finely decorated face with a fixed hour circle showing the Zodiac and a smaller disk rotating clockwise. The latter carries six openings. Inside five of these, the five planets then known?Saturn, Jupiter, Venus, Mars, and Mercury?rotate counterclockwise. The sixth opening contains the Dragon, indicating the lunar nodes and eclipses. In the center, two overlapping disks show the phases and ages of the Moon and the index of the Sun. The driving trains?of unprecedented complexity?are arranged vertically on parallel planes.

The clock is accompanied by two globes?one celestial, the other terrestrial?as well as a sophisticated chime mechanism. All of the clock's incredibly varied movements are driven by a single weight-powered motor.

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