History of Mechanical
Tower Clocks
The only information we have about the first mechanical clocks derives from descriptions found in ancient manuscripts. There are no examples of these early clocks, whose origins were in the early monasteries where they were used as alarms to wake the brothers for their daily prayers. The first mechanical clock created was based on a clepsydra (an early water clock) like the "celestial machine" built in China by Su Sung during the eleventh century. In Europe, water was used to provide power to the clock; it was very soon replaced by a stone or metal weight. We have no idea of the date of that development. We do know however, that an early clock was mentioned in Dante Alighieri's (1265-1321) Divina Commedia (Paradiso, XXIV, 13), which leads us to the conclusion that the mechanical movement appeared relatively late. The word horologium in those days had a very general meaning, referring not only to the mechanical movement of a clock, but also any other device used to measure the passage of time.
Despite the existence of a document from 1176, we do not know which sort of clock was the one in the Cathedral of Sens, or the one in the "house of the clock", gothic tower of four floors where the scheme is reproduced in the manuscript from the XIII century of the architect Villard de Honnecourt. The word clockmaker that in the Middle Ages includes all sorts of devices for measuring time, does not show us the kind of clock that the Clockmakers of Colonia built in those times, where they called a street with the name of Horologiengasse. The situation is about the same in all the countries of Europe: we ignore all the monumental British clocks, particularly the ones in Westminster (1288), Exess (1284) and Canterbury (1292). We also do not know how was the clock built in Florence in 1300, neither the one in the Cathedral of Beauvais, all from the same age. They could be a sun quadrant, and in that case a bellman of the city would be in charge of banging the bells as indicated. This eventuality stays in the ordinance of the Bishop of Corbeil. The use of a clepsidra with carillon with similar circumstances was also thought. Opposite to that, we are almost totally sure that the clock of two weights built in silver in 1299 or 1314 for "Phillip IV el Hermoso", was a mechanical clock; its builder probably was the jeweller from Paris, Pierre Pippelard, one of the eldest clockmakers, whose name arrived up to today, with the names of Jehan Aurologier (1292) and Robert from England. The last one, Robertus Anglicus already talks about the escapement of the clock; but unfortunately his manuscript has no date, but it is thought that he lived and worked in the beginning of the XIII century; it is not excluded that this regulator worked in a monumental clock already used.
In the "Roman de la Rose", written before 1305, the poet Jean de Meung makes allusion to the movement and the bells. The sumptuous clock of Cambrai, built in 1318 by Colard LeRvre, as it shows the detailed lists established by the technical and artistic works, should have been provided by a escapement system. These receipts testify the existence of a sophisticated astronomic device, completed by the representation of the sun and moon trajectories, a calendar and the zodiac signs. This clock was provided of automates, painted figures of apostles and angels that signed the date in the calendar. It was an authentic monumental clock of the middle age, that under certain aspects, it remembers us the one in the Prague Town Hall . Such device needed a very perfect mechanical movement.
In 1333, it is installed in Milan a public clock with sonery and whose face showed the Italian time. Also overreaches the monumental clock of Saint-Jacques de L'Hópital, built in 1334 in Paris, near Saint Denis. It was very sumptuous but terribly inexact, that is why it was changed in 1399 by a clock built by Jehan Ray, with the collaboration of Jehan Guignon. This last one added automates, that were wooden angels sculpted by Thomas Privé, and they banged the bells. This clock served as a time reference during the whole XV century, and from this fact we have a great amount of documents. So we know that in 1473, an automata which represented a "savage", sculpted and painted by Guillaume Santé replaced the angels.
Since the second half of the XIV century, the craft of clockmaking was already very solidly inserted in the big cultural centres of Europe: Florence, specially in Francia, Alemania and also in Flandes and Bohemia. The emperor Charles IV, per example, had his clockmaker called Martin in his court, in 1376. Unfortunately we ignore which type of clocks he was in charged. We can suppose they were little interior mechanical clocks, like the ones that the nephew of Charles IV had. The king of France Charles V asked his clockmaker of Sainte Beate, a journey model in silver and that was done by fixing the famous clock of his ancestor Phillip IV "el hermoso". In 1370 was built a monumental clock, placed on the front of the Royal Palace of Paris, «to help the inhabitants of the city, to take care of their business during the day and also the night». This clock was designed by Henri de Vic. Between the goods of his succession, Charles V left a silver clock over a support. It was an authentic mechanical movement clock with weights, as it was represented in a little draw of those times Charles V also had a huge sand clock, that was rarely used in his time, and a palmatory clock.
"Il Tractatus Astrarii" of Dondi
In the second half of the XIV century, the clocks existed in other big cities and feudal castles in France, like the one in Comillon. The clockmaker Giovanni di Dondi, nicknamed Dell Orologio, published in Padua a writing whose title was "Il Tractatus Astarii" . In this work Giovanni di Dondi describes a model of astronomic clock that himself drawed in about 1364. This description gave us valuable data about the way many old clocks were built. This model was built in two examples by Peter Haiward (one of them is presently in the Smithsonian Institution of Washington, and the other one in the Science Museum of London). It was a metal heptagon placed on a high pedestal in each side of the faces that showed the solar time and the sideral time. It was a wooden clock unique in his gender, it was two centuries advanced over its time, as the point of view of astronomical knowledge as the one of time measuring. The reconstruction of this clock was presented in Nuremberg in 1978, during the great exposition about Charles IV. Dondi (1330-1389), son of the doctor and physician Jacopo di Dondi, author in 1344 of the monumental clock of Padua, was at the same time the personal doctor of the emperor.
Other drawings that illustrate manuscripts of the XIV century (where some of them were completely dedicated to clockmaking) are less important. But there are some of them well known, per example the work titled "Livre de l'Horloge de Sapience" , that belonged to Mary, granddaughter of the king of France Charles V. This writing; that was finished in 1406 and conserved up to these days in the national Library of Paris; has a big picture representing the rudimentary shape of a mechanical movement clock. Such a clock, called «bird cage», whose chassis was four pillars and a little bell, had four faces with a disc shape, where the centre is a star with twelve hands with the hour marks, and a crown painted in white. In those times the time marking systems (dials) were mobile, turning under a fixed hand placed on the clock chassis. The mobile hand did not appear until the beginning of the XV century, and only in the XVI century would be added the second hand.
"Livre de l'Horloge de Sapience"
We find a more detailed representation of the clock in a later edition of the Horloge de Sapience, dated approximately in 1450, and in the manuscript of Christine de Pisan and Nicolás d'Oresme , courtesans of Charles V. We find it again in copies of this work of the middle of the XV century. In the Vatican Library it is conserved a manuscript of the endings of the XIV century, containing a detailed description of a sonery mechanism. It is compound by seven wheels connected to the time system; the movement was placed in a simple rectangular frame. it was built in forged iron; this description corresponds exactly to the drawings of the clock, not only in its general aspect but also in the number of wheels and the way of adjusting them. The mechanism has an interesting piece, that it is a kind of brake, a wings wheel whose function is to control the movement of the wheels with the resistance of the air.
Thanks a lot to Donn Lathrop for helping with the english version.