Probably nobody knows that the larger collection in our National Museum of Science and Technology is the clock section with over 1,000 pieces, from the first measurement devices, such as an Egyptian hourglass; or the so called “Notturno” by Johann Philipp Treffler, a German clockmaker of Augsburg, involved in a controversy on the priority of the application of the clock pendulum; or the revised mechanism for using the pendulum on Galileo Galilei’s design.
But doubtless the most incredible piece of the section is the Astrarium by Giovanni Dondi dell’Orologio (the nickname “dell’Orologio” means “of the Clock”) since he created, between 1348 and 1364, not only the first mechanical clock to be built in Europe, but a huge continuous display of the major elements of the solar system and a day-by-day calendar with legal, religious, and civil annual recurrences. Dondi’s intention was to help people’s understanding of astronomical and astrological concepts, since astrology in his time was considered a science worthy of study by the intellectual elite.
For getting data on the motion of the planets, Dondi consulted the “Alfonsine tables”, named after Alfonso X of Castile, who sponsored the compilation of this data in Toledo, Spain, starting from January 1st 1252, the date of his coronation.
One of the 107 gear wheels and pinions
After this preliminary point, Dondi conceived his Astrarium with 107 gear wheels and pinions, entirely handmade, using no screws, since every part was held together by over 300 tapering pins and wedges, with only some parts soldered. Most of the wheels have triangular shaped teeth, although some are blunt-nosed. In some cases, Dondi used near-elliptical wheels, in order to more accurately model the irregular motions of the planets (using the Ptolemaic epicycles rather than the ellipses as later worked out by Johannes Kepler). On some of these wheels, the teeth varied in size and spacing along the periphery.
The Astrarium
The Astrarium was about 1 metre high, and consisted of a seven-sided brass or iron framework resting on 7 decorative paw-shaped feet. In the lower section, a 24-hour dial and a large calendar drum, showing the sunrise and sunset time for each day (at the latitude for Padua, his home town near Venice), the “Sunday letter” that determines the succession of days of the week, the saints’ days, the date of the fixed and the movable feasts of the Church, and even the position in the zodiac of the Moon’s ascending node. The upper section contained 7 dials, each about 30 centimeters in diameter, showing the positional data for the Primum Mobile, (namely the “first moved”, the outermost moving sphere in the geocentric model of the universe) with Venus, Mercury, the Moon, Saturn, Jupiter, and Mars (the only planets known at the time).
In 1381 Dondi presented his clock to Gian Galeazzo Visconti, duke of Milan, who installed it in the library of his castle in Pavia, where presumably it was kept for the rest of its life. The last related news about the Astrarium dates back to 1529 when it was mentioned by Janello Torriani, a skilled blacksmith, watchmaker, ingenious hydraulic engineer, court mathematician and celebrated inventor, who was part of the entourage on occasion of the arrival in Italy by Charles V, King of Spain and Emperor of the Holy Roman Empire. At that time Torriani described it as in poor condition and in need of maintenance, but nevertheless he was fascinated by its incredible technology and personally executed several other similar mechanical copies.
Perhaps the Astrarium was then destroyed in subsequent years.
Luckily, Dondi left a comprehensive Tractatus Astrarii (Treatise about the Astrarium), a manuscript, now preserved in the Chapter Library of Padua, where he described the work of design and construction of his astronomical clock, with accurate details of the more complex components, not always so terrifically simple to understand since he indicates some units dimensions such as the width of a goose quill, the thickness of a blade of a knife, or the breadth of a man’s thumb …
Nevertheless, his writings allowed some modern clockmakers to reproduce convincing copies. Seven reconstructions were built by Peter Haward of Thwaites and Reed, in London (a manufacturer which claims to be the oldest clock manufacturing company in the world); and examples of these can be found in the Washington Smithsonian Institution and The Time Museum of Illinois.
More recently the watchmaker Luigi Pippa worked on three reconstructions.
The Sun
One is at the famous Musée International d’Horologerie, La Chaux-de-Fonds, in Switzerland (of course!).
A second at the University of Padua, but certainly the most accurate and scientific, produced in 1963, is normally kept in Milan at the Museo Nazionale della Scienza e della Tecnologia as the masterpiece of the Clock section.It is currently on loan to the city of Cremona, until the 29th January 2017, on occasion of the Janello Torriani exhibition held in Palazzo dell’Arte, Museo del Violino, Piazza Marconi, Cremona (PC) to underline the personality of this Renaissance genius who built the most complex machines, was forgotten for centuries, and only recently unveiled.This could be a worthwhile occasion for a visit to the beautiful town only 100 km south Milan, the home town of the violinist Antonio Stradivari, considered the most significant and greatest luthier and crafter of stringed instruments; participate in the Stradivari Festival from the 9th of October; and eat a bit of the typical sweet called torrone.But of course, if you can wait until February you should definitely pay a visit to the large Clocks section of the Milanese museum and be astonished by the incredible mechanics of the Astrarium!
Museo Nazionale della Scienza e della Tecnologia Leonardo da Vinci, Via San Vittore 21 • M2 Sant’Ambrogio
(photos by @AndreaBOSSOLA)
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