The Development of the Clock and the Concept
of Time in the Middle Ages
- The various instruments used for keeping time are all measuring
devices and thus in some senses scientific instruments. The most
extraordinary of these devices is the mechanical clock: a most
remarkable and in some ways unexpected instrument. Certainly
it was the most complex scientific instrument of the middle ages,
and in many ways seems unprecedented.
- It is thought that the mechanical clock was invented in Western
Europe around 1300 CE. The exact date is difficult to establish
because no clocks from this period are extant, and because the
terms used to describe early clocks were also used to describe
clepsydra or water-clocks. One of the most remarkable aspects
of the clock is that some of the earliest known examples were
also incredibly complex. An example is the Astrarium completed
by Geovanni di Dondi, an Italian astrologer/physician in 1364.
This clock is well known because di Dondi left detailed plans
for its construction (at least three replicas exist: at the Science
Museum, London; at the Smithsonian, Washington D.C.; and one
owned by IBM Corp.). This clock had seven faces which displayed
the positions of the stars (as on an astrolabe's face), the positions
of various planets, the moon's position etc., it was a complex,
multiple-display astronomical device. This device is unlikely
to have arisen from nowhere. It turns out we now know that astronomical
gearwork goes far back into antiquity (e.g. the Antikythera device,
an astronomical computer of c. 50 BCE, a geared Byzantine Sundial/calendar
of c. 520 CE, and various geared astrolabes of c. 1200-1300 CE).
- But gearwork is only half of the problem of the origin of
the clock-the other is the origin of the escapement. This mechanism
truly seems to be a medieval invention. Are there again precedents?
First alarm bells of medieval timers had an oscillating action.
Second, we know the Chinese invented an escapement of a different
sort (C. 1090), but there is no evidence of its diffusion, and
indeed the technology was quickly lost in China itself.
- We have been dealing with technical aspects of the clock's
origins. What about need-who cared? First the Monastic orders:
there were specific requirements for times of prayer. But these
times were better measured with sundials or water clocks because
they needed unequal hours, that is hours proportional to day
length, which in Northern Europe varies significantly with the
season! (Of course in Northern Europe the sun is often obscured
by clouds and water clocks may freeze in the winter!) And, until
the invention of the pendulum clock, water clocks were capable
of greater accuracy! The second group would be astronomers and
medical astrologers. They wanted equal hours, the hours of the
planets and stars-God's hours. For them the clock was a conscious
model of the solar system. It could then of course also become
a valuable theological model once it was perfected.
- The clock quickly became one of the great symbols of the
medieval period. Building a clock was their equivalent of the
Apollo Project: an incredibly expensive venture requiring the
services of the most highly trained scientists and technicians
of the culture and a large investment of material.
- Examples of Some Clocks and Time Keeping Instruments Typical
of the Middle Ages
Dial: Modeled after a medieval instrument found in the walls
of Canterbury Cathedral.
Perfected by the Arabs, this instrument was developed by the
Greeks as early as the 2nd century B.C. The oldest extant examples
are 10th (Islamic) & 13th (Christian) century.
- Nocturnal: Described by Raymond Lull in the 13th century
this instrument enable time telling at night by the position
of the stars. This commercial model is of a 17th century instrument.
- Water Clock
(Clepsydra): All of the features of this water clock were known
to the ancient Greeks, as well as in the Middle ages(c. 135 BCE,
DSL Fig 2).
- Sand Glasses: Thought to have been invented in the Mediterranean
area in the 12th century (GLT 15), possibly associated with the
use of the compass and portolan chart and traverse board. They
became more common after the invention of the mechanical clock,
probably due to the acceptance of equal hours occasioned by the
- Bracket Clock with Verge and Foliot Escapement: The escapement
clock was invented in Europe about 1300. The verge and foliot,
as in the example, does not have a fundamental frequency however,
and the accurate, precision clock had to wait the invention of
the pendulum clock by Galileo and Huygens in the 17th century.
Escapement clocks could only conveniently keep equal hours (as
used by astronomers), thus forcing European society to equal
hours over the traditional unequal hours of former time.
- DSL= Landes, David S. Revolution in Time. Belnap Press,
Cambridge Mass. (1983).
- GLT= Turner, Gerard L'E. Antique Scientific Instruments.
Blanford Press. Poole (1980).
© R. Paselk
Last modified 6 August 1999