The dial-plate is unusual: to know the time you have to make the sum of the indications given by the little spheres disposed along the three horizontal lines. The balls-clock works by means of an electric motor that makes its long back arm rotate. This arm is equipped by a spoon to lift a ball up every minute and put it down on high. Thus the ball slips down and stops on the minutesí line (the higher one). When the fifth ball stops on the minutesí line, the mechanism takes back to the lower store all the balls but one who goes to the five-minuteís line (the intermediate line where each ball corresponds to 5 minutes). At its turn, when this line is full of balls (after 60 minutes) all the balls go back to the store, but one who goes to the hoursí line (the lower one).
In conclusion this clock has only an odd dial-plate. For the rest it is based on a general principle common to all clocks: the exploitation of a periodic motion - in this case on the rotating motion produced by an electric motor - able to beat the passing time regularly.

A brief note in the end: the clock has been inserted in this section because the astronomy and the time measurement have been always strictly connected.