Gnomon's Guide

Every day in the Old Town Square in Prague, capital of the Czech Republic, a crowd of hundreds of people gathers to witness a unique event: the chiming of the Astronomical Clock.

Mounted on the tower of the Old Town Hall, Prague's Astronomical Clock is one of the oldest and one of the most elaborate clocks ever built. Some parts of it are nearly 600 years old, making it almost as old as the clock in Wells Cathedral. It has two main dials (clock faces), one directly over the other, and numerous wooden figures which are animated when the clock chimes the hour.

This type of clock with animated figures and bells is sometimes called a glockenspiel which means literally 'bell play', although the name is also used for a type of musical instrument.

Chiming the Hour

During the day (9am to 9pm), the clock performs on the hour.

• To the right of the main dial, a figure of Death in the form of a skeleton starts the show by inverting the hourglass in his hand. Beside him, a figure of a Turk shakes his head.
• On the other side of the main dial are two of the Seven Deadly Sins. A figure representing Vanity admires himself in a hand mirror. Beside him, Avarice waves a bag of money.
• Above the main dial, two doors open. Inside we can see a procession of 12 saints; these are St Paul and the 11 faithful apostles. (Judas the betrayer is not included). The saints march past the windows, each one turning to look out as he reaches the window.
• When all the saints have looked out, the doors shut, a cock crows and a bell chimes the hour. A twenty-four hour format is used for the bell, so that, for example, at 3pm it chimes 15 times.

The Astronomical Dial

The main dial of the clock looks nothing like a modern clock. It is packed with information, giving not only the time but the positions of the sun and moon. This dial is the original one, built in 1410 by the clock maker Mikulas. The clock was originally intended purely to provide astronomical information. The rest of the clock was added much later. The dial features the following:

• Around the outside of the dial are two circles of numerals. The inner circle is in Roman numerals; the hours as we know them are marked around the circle. All twenty four hours of the day are marked, with 12 noon at the top and 12 midnight at the bottom. An hour hand points to the current time. There is no minute hand - people didn't worry about such small units of time in 1410. The pointer on the hour hand is in fact a golden hand, with fingers and thumb.
• The outer circle is inscribed with Arabic numerals (1,2,3 etc up as far as 24). These show 'Old Bohemian Time'. This is the number of hours since sunset. Since the time of sunset varies during the year, this circle of numbers rotates relative to the fixed Roman Numerals, a fact which is not obvious when looking at the clock.
• Mounted on the hour hand is another smaller dial showing the twelve signs of the zodiac. A golden sun and a silver moon show the positions of the sun and moon against the stars. The moon is painted half black. It rotates so that it shows the correct phase of the moon.
• The main dial is painted in blue, red and black, representing day, twilight and night. The position of the sun against these shows the current state. Also on the main dial are lines dividing the day into the hours of 'Babylonian Time'. These divide the daylight into 12 hours, so the hours themselves vary in length with the seasons.

The Calendar Dial

The calendar dial is directly below the main dial. It was added to the clock in 1490. Around this dial are the 365 days of the year. The days rotate so that today's date is on top, indicated by a fixed golden pointer. The centre of the dial is purely decorative. In 1865 the clock was refurbished and the present decorative panel was added. It was painted by Josef Mánes and shows scenes from Bohemian peasant life representing the 12 months of the year, as well as the 12 signs of the zodiac.

The Animated Figures

The four animated figures around the main dial were added in the 17th century. Four figures, including an angel with a sword, were also added around the calendar dial, although they are not animated.

The procession of saints was constructed when the clock was refurbished in 1865, making it the most recent addition.

But what time is it really?

For those who can't figure out how to read the main dial, there are two normal dials at the side of the tower. The clock would originally have kept local time, but now shows Central European Time. The zodiac dial would probably have originally shown the actual position of the sun in the zodiac, but now instead it shows the zodiac signs as used by modern-day astrologers and horoscope writers. No doubt this makes life easier for the person who looks after the clock.

Further Information

For a picture of the clock, go to The Glass, Steel and Stone Site.