A first small flight of stone steps leads up to a little room in which the history of the Tower is explained. From here one can see the interesting network of pulleys, weights and counterweights as they silently rise and fall at regular intervals. A metal spiral staircase then takes one towards the complex workings of the clock proper; visitors get a close view of the mechanism and of the gears linking it with the south and north clock faces, overlooking St. Mark’s Square and the Mercerie respectively. A further staircase then leads up to the next floor, where one can see the wooden statues of the Magi and the Angel as well as the two ornate doors from which these statues emerge in procession twice a year (on the feasts of the Epiphany and the Ascension). Here visitors can also see inside the mechanism of the clock barrels which indicate the hours and the minutes. Going even higher in the Tower one comes to a room which holds components from the 15th century clock mechanism. From here one can go out onto the two side terraces and, via a steep spiral staircase, up to the Two Moors Terrace, where one not only gets a close glimpse of the two colossal statues but also a splendid view of Venice and its lagoon.
The Clock machinery. The heart of the Clock is a complicated system of gear wheels located within a large cruciform metal framework at the center of the Tower. The true ‘engine’ of the entire timepiece, this can be broadly divided into 4 distinct sections; along with these there is the machinery for the astronomical clock face and the workings of the clock barrels. Also known as ‘clock trains’, these 4 sections are similar in appearance and basically comprise: a barrel around which is wound a chain (formerly a rope) to which is attached the motor weight (100 kgs); an intermediate wheel; a rotating fan that serves as an aerodynamic brake to regulate the weight’s speed of descent and thus the interval between clock strokes. The fans are equipped with a ratchet that makes a very recognisable sound; this is activated at the end of each series of strokes and serves to disperse the accumulated kinetic energy when the rotating mechanism comes to an abrupt halt. The clock train transmits the impulses which enable the pendulum to continue its isochronic oscillations (the very basis of the mechanism’s precision). It also comes into play at fixed intervals to trigger the other trains of wheels and pins. By means of thin vertical rods, it activates the barrel machinery every 5 minutes; as a result the minute barrel rotates through 30° (1/12 of a turn). Every 60 minutes, the hour barrel does the same. Upon each hour, the train mechanism for the Two Moors is activated. Two minutes before the hour, the Moor on the right strikes the bell; two minute after the hour, it is the turn of the Moor on the left. This is why the mechanism is described as a ‘re-striking’ one. With the hammers they hold, each Moor strikes the bell on the top of the tower a total of from one to twelve blows, depending upon the hour. Finally, every 12 hours, the 132-stroke train is set in motion. These 132 ‘meridian’ strokes occur at midday and midnight before the Moors strike the bell. They are rung by 2 supplementary hammers placed around the circumference of the bell; the number of strokes corresponds to that of the strokes hit by the two Moors in the previous 11 hours. The barrel mechanism also operates the astronomical machinery via the Moors wheel, which goes through a complete rotation every two hours, and a 22-tooth pinion. This latter goes through 12 rotations a day, turning all 264 teeth (22×12) on the large wheel, which turns the sun clock-hand through one entire circuit per day. Finally, via a return mechanism and a long axle under the clock machinery, the Barrel Mechanism also operates the hour hand on the clock face giving onto the Mercerie. The whole thing is driven by means of 5 train mechanisms, periodically recharged by the raising of the weights. The pendulum and the anchor escapement regulate the perfect release of energy, so that the mechanism works in a constant, even manner. Still perfectly functional, the entire structure dates back to 1753-57, when Bartolomeo Ferracina significantly modified the original machinery built at the end of the 15th century by G. Carlo Ranieri.
The Three Kings and the Angel. When the Clock Tower was built in 1499, the Three Kings and the Angel with the Trumpet were designed to come out every hour from the loggia on the second storey of the structure and pass in procession before the statue of the Madonna and Child. However, the delicacy of the complex mechanism meant it was subject to great wear and tear over time, so eventually the procession had to be reduced in frequency or stopped altogether. After Ferracina had re-designed the clock mechanism, he also worked on that governing the procession (1758-159); still in use today, it comes into operation only twice a year: on the Epiphany and the Feast of the Ascension. The actual wooden statues of the Three Kings and the Angel were re-done by Giovanni Battista Alviero in 1755; as stratigraphical tests – and various inscriptions in the machine housing – show, these rather crude works have been restored and completely repainted on several times.
The doors. Originally, the doors from which the Three Kings and the Angel emerged in procession were wooden structures covered with painted and gilded metal and decorated with two gilded angels in embossed metal. In 1858, these doors have been absent for most of the year, replaced by two metal openings which are decorated with gilded geometric motifs and make it possible to reading the panels of the hours and minutes on the rotating barrels installed by Luigi De Lucia.
The barrels. The two rotating frames with the panels showing the hours and minutes were created and installed in 1858 by Luigi De Lucia; designed to make it easier for those down in St. Mark’s Square to get a more precise idea of the time, they are among the first examples of this kind of mechanism in a public clock. The two barrels each bear twelve panels of 80 by 50 cms; one with the hours in Roman numerals, the other with intervals of five minutes in Arabic numerals. Once lighted from inside the barrels, the panels are made of sheets of blue-tinted zinc. The installation of this mechanism blocked the movement of the Three Kings, so twice a year a special mechanism to raise and lift it backwards comes into play, freeing access to the doors and the notched circle along which the Three Kings and the Angel move in procession before the statue of the Madonna.
The Moors and the bell. The two giant statues in bronze (traditionally known as “The Moors” because of the patina on the metal) were cast in 1497 by Ambrogio della Ancore; the body is hinged at the waist to permit the movement made in striking the bell. In spite of their function, the modelling of the statues deliberately exaggerates their mass, so that their form is unmistakable, even from a great distance. The bell, surmounted by a gilded sphere and a cross, was also cast in 1497. It was the work of a certain Simeone, who has signed his name with a fine inscription in the bronze. During the mid 19th century replacement of the roofing to the Tower, the bell and the two Moors were raised about a metre above their original level.