Astronomical Clocks of the Middle Ages
A Guided Tour (Part 2)
In Part 2 we look at some extant examples of medieval
astronomical clocks, from all over Europe. We include links to
web-sites with photos and further information about these clocks.
|Note Each external
link will open in a new window. To return to this article
just close the new window (click X at top right hand
Stage 0: No Dial
One of the oldest surviving mechanical clocks in the world is
the one in Salisbury Cathedral, made in about
1386. The clock has no dial, its sole function is to strike the
Stage 1: Moving dial
A few clocks with moving dials survive in museums.
Stage 2: Sun-Clock
This stage is purely theoretical: no examples known to the
Stage 3: Sun-Moon
Here we're on safer ground. There are several examples of
sun-moon clocks in the West of England:
- a famous one in Wells Cathedral (click here for a picture). Dates from the second half of the 14th
- a somewhat less elaborate example at Exeter
Cathedral, dating from 1423 (click here for a picture).
- still humbler examples at the parish church of Ottery
St. Mary (Devon) (picture) and at Wimbourne
Stage 4: Sun-Moon-Zodiac
- Padua One of the earliest public clocks
of this type was built by Jacopo de Dondi (father of
Giovanni de Dondi of Astrarium
fame) at Padua in 1344. Unfortunately this clock was
destroyed in fighting between Padua and Milan in 1390.
However it was replaced in 1423 by the present,
magnificent clock (believed to be similar to the original
one). Click here for a picture (J.Podosky's site;
see Prague below). The purpose of the geometric figures
at the centre is to enable one to tell at a glance
whether the moon is making a significant astrological
aspect to the sun (e.g. 90 degrees, 120 degrees etc.).
- Venice The famous clock in St. Mark's
Square, housed in the Torre del' Orologio, completed
1499. The clock was recently restored by the Swiss firm
Piaget. For a good
photo of the clock-face have a look at this on-line article about the clock (scroll down to the 4th picture, and click on it). It is
believed that at the centre of the clock-face there were
once concentric rings carrying emblems of the planets,
showing the mean motion of the planets about the earth.
Alternatively, there may have been more elaborate dials
(similar to those on de Dondi's Astrarium),
showing the true positions of the planets as they appear
to us. Note the first hour beginning at what we would
call the 3 o'clock position: a relic of the old Italian
system of reckoning 24 hours from sunset to sunset.
- Hampton Court Palace (1540) - click here for a picture. The palace built by Cardinal
Wolsey and 'given' to Henry VIII in 1528. The clock
probably designed by Nicholas Kratzer, the subject of a
well-known portrait by Hans Holbein (note the
Stage 5: Astrolabe Variant
- Prague. Built 1410, at the Town Hall.
Believed to be essentially unaltered (including the clock
mechanism) since it was built. See the excellent picture at J.Podolsky's web-page about the clock (part of the
web-site of the Relativity Group at Charles University,
- Lund Cathedral. The original clock goes
back to 1380, but it was restored in the 1920's. Find it in this
virtual tour of the interior of the cathedral.
- Berne - the Zytgloggeturm (clock tower); dates