The Zimmer tower in Lier - the world's slowest mechanical construction

In the city of Lier, not far from Antwerp, stands the Cornelius tower, a last remnant of the city’s medieval fortification. Today, it is better known as the Zimmer tower, because of the unique clocks it hosts from watchmaker and self-made astronomer Louis Zimmer.

Even if you’re not much interested in clockmaking and telling time, this is a unique visit well worth your while, since it includes three master-pieces with world-wide fame: the Jubilee Clock and Astronomical Studio in the tower, and the Wonderclock in a nearby pavillion.

In total, these 3 constructions have 163 dials, but are driven by only 2 clock mechanisms. Why in the world would one need 163 dials to tell time? What do they show?

• Measurements of time: of course time itself, in various timezones, as well as day of the month, day of the week, month, season, zodiac, the decimal hour, sideral time, …. Note that we’re well before the electronics age, and all variables are mechanically calculated, driven by 2 mechanisms only.
• Phenomena driven by time: astronomical phenomena, such as the lunar cycle, distance between earth and sun, earth’s velocity, sunrise and sunset, tides in 10 cities, …

The Wonderclock is a 2041 kg, 4 m high construction developed for the 1935 World Fair in Brussels. In 1938, it was shipped to New York for the 1939 World Fair. Due to the War, it returned to Lier only in 1954. The clock has 93 panels. The time of one revolution varies between an hour and 25,800 years - a variation of 8 orders of magnitude. The panel requiring 25,800 years for one turn is subdivided in 360 degrees and needs 71.66 years to move one degree, making it the slowest mechanism in the world. This panel shows the ‘general precession of the earth’s equinoxes’.

The Jubilee Clock was donated by Louis Zimmer in 1930 to his birth town. It commemorated the 100th anniversary of Belgium. The clock was built into the Cornelius tower which was quickly renamed. It consists of a central panel showing the official time in Belgium, surrounded by 12 panels:

1. Equation of time
2. Zodiac
3. Solar orb and dominical letter
4. The week
5. The terrestrial globe
6. The months
7. The dates
8. The seasons
9. Tides
10. Moon’s age
11. Phases of the moon
12. Moon’s orbit with EPACT

The astronomical studio on the first floor of the tower consists of 9 departments with 57 astronomical representations. It was finished in 1932 as a didactic display for schools, a purpose it serves until today.

Noteworthy

• Until 1940, Amsterdam operated on a special time zone UT+20’. There were 40 minutes of time difference between Amsterdam and Brussels.
• The Chinese dial, where the hands turn in the opposite direction.
• The decimal time: During the French revolution, the day was divided in 10 hours, with each hour having 100 minutes. Midday was 5 o’clock, midnight 10 o’clock. The introduction of decimal time was rather short-lived.
• Thirteen dials in the astronomical studio show the tides in various cities. There is a time delay between the passing of the moon and the beginning of high water tide, caused by depth, channels and friction of the borders. From Lisbon to Reykjavik, this time difference amounts to almost 16 hours.
• The Cotsworth calendar was developed n 1902, and proposed in 1932 to the League of Nations. It consisted of 13 months of 28 days each. The 13th month, Sol, is inserted between June and July. A 365th day is added as international Day of Peace. This calendar is a universal calendar, with your birthday falling each year on the same day of the week. We can understand the appeal of this calendar to Louis Zimmer, as it greatly simplified the required mechanical calculations compared to the Gregorian calendar.