World's first clock? Perhaps.
The original Zodiacal clock sat in the tower of the Palazzo Capitanio in Padua, Veneto, otherwise known as Padova (where armistice was signed at the end of WW1). The Palace closes one end of the Piazza dei Signori, and was the home of local government.
This public clock, which was built in 1344, was a commission from Prince Ubertino de Carrara, who probably 'helped' in its external appearance. But the functional design was by Jacopo de'Dondi (1290-1359) who also supervised its construction. It may not actually have been the world's first clock ever but it was certainly one of them.
Jacopo had graduated from the famed Padua University (established 1222) to become the municipal physician of Chioggia, where the family originated and still lived. But he later returned to Padua as professor to lecture at the University's medical school. However, like many medical scholars of the time, he was fascinated by the sky and the stars, and by how time was calculated according to the movement of the sun.
The clock has a 24 hour dial, so the hour hand rotates at half normal speed (only once a day, not twice), pointing down at midday instead of up. It strikes the hours on a bell from 1 to 24, too. It also shows the position of the sun in the zodiac, and the current phase of the moon. The geometric figures at the centre help astronomy scholars to see at glance the astrological aspect of the moon in relation to the sun.
So it is a complex and very advanced clock for its time. Sadly, however, it was destroyed either in 1390 when armies from Milan took control, storming the Palace and burning it down, or in 1399 when the Venetians siege the city to snatch it back. So it cannot be given the title of the World's oldest clock.
These images actually illustrate the replacement clock, which was built in 1423, which is said to be a faithful copy of the original, save possibly for one aspect: it is missing one of the Zodiac symbols, Libra. Look how the crab (Cancer) occupies a double space. Fable has it that the builder deliberately omitted the Libra symbol because he was disgruntled at not being paid the price to which he thought he was entitled for his effort! However, another version of the story is that Libra was also missing from De'Dondi's original, too, as a protest by Jacopo for a town that suffered extreme injustice under the harsh rule of the Carraresi family.
Jacopo's son, Giovanni de'Dondi, is possibly better known, keeping up the family's horological tradition by constructing a miniature but very complex planetarium or Astrarium - a one metre tall clock with Ptolemy's seven dials, and an advanced two-second foliot verge escapement. It showed the date, and the movement of the sun, the moon and all the five planets that were known at the time (Mercury, Venus, Mars, Jupiter and Saturn). Earth, of course, was at the centre. It took him sixteen years to design and build and the family became so renowned as early horologists that they re-styled the family name "Dondi dell'Orologio".
This article was orignally published by horilogica. The article can be found here.