St Mark's Clock

After restorations in 1551 by Giuseppe Mazzoleni, and in 1615, by Giovanni Battista Santi, the clock mechanism was almost completely replaced in the 1750s, by Bartolomeo Ferracina.

Driven by weights, with a foliot escapement, the clock controlled both the bell-ringing shepherds on the tower, who would have rung the bell between 1 and 24 times to sound the Italian hours, and a carousel which showed the procession of the Magi, preceded by an angel blowing a trumpet.

In 1752 Bartolomeo Ferracina started work on replacing the clock, having successfully tendered for the job in public competition.

He installed a new movement, removed the planetary dials, installed a rotating moon ball to show the phase, and changed the numbering of the clock face from the old Italian style (I to XXIIII in Roman numerals) to the 12-hour style, using two sets of Arabic numerals, with 12 at the top and bottom of the dial.

A Graham dead-beat escapement replaced the foliot, with a 4m pendulum, mounted away from the central arbor, beating once every 1.97 seconds.

During the Magi procession, the wheels were lifted away from the doors to allow the statues to pass through, and the temperatore changed the numbers manually.

As a result, the hour hand moves slowly anticlockwise relative to the zodiac, so that it passes through each sign in the course of the year.

The Venetian authorities did not submit the job to open tender, but chose Giuseppe Brusa, historian, and Alberto Gorla, clock mechanic, directly.

Articles written by Renato and Franco Zamberlan, and published in the British Horological Journal in 2001, accuse Brusa and Gorla of poor choices, unsound restoration methodology and inappropriate workmanship.

Rather than make minimal interventions, as modern conservation practice requires, the restorers made considerable changes to the design.