Proceedings 21        13 December 1990        at the Warburg Institute, Woburn Square, and London

DEVELOPMENTS IN MECHANICAL CLOCKWORK IN THE LATER MIDDLE AGES, an illustrated paper by Mr. J.H. Leopold of the British Museum.

The President being unfortunately unable to attend, at the invitation of the Vice President the Secretary chaired the meeting.


By way of preface, the speaker observed that the history of mechanical clockwork was confused and the sources scanty and at times ambiguous. For example, the ward horologic could not only mean sundial, water-clock or later mechanical clock, but in German sources was liable to be confused with the old German word Orlogium for war [cf. modern Dutch Oorlog, ed.] The water clock, antecessor and probably dating back to Babylon, was well known in Greek and Roman sources.

There was no further mention of the water clock in western European sources after the 560s (apart from one reputedly sent to Charlemagne by Haroun al Raschid) until AD 1000. Then one found mentions of clepsydra and water clocks as alarms in monasteries. From ca.1100 came a fairly full description of one with alarm mechanism operated through pulleys and weights. The report that during the great fire at Bury St. Edmunds in 1198 water was drained from the orologium to fight the flames, made telling evidence of the size of such apparatus. Early in the 13th c. St Hermann Joseph of Steinfeld is recorded as a maker of water clocks. A contemporary MS illumination (1230s) showed King Hezekiah with a water clock driven by a toothed wheel apparently contrived to strike a range of bells above it. From 1232 we had a record of the 'tentorum' with a 'planetary device' given by the ruler of Damascus to the Emperor Frederick II.

The mechanical clock was definitely a western invention. In 1271 Robertus Anglicus comments that contemporary clockmakers are working on the problem of how to construct a wheel that would revolve slowly and regularly.  This is generally taken as proof that no mechanical clock existed at this time. Au contraire it could be argued that wheeled clocks of a primitive kind were already in existence and makers were now in search of mechanisms of greater precision. The problem was to derive slow revolutions -from small fast moving wheels with ordinary teeth and lantern pinions. The verge escapement facilitated the conversion of rotary motion to alternating motion with a balance. Other 13th century records included tantalizing references to Dunstable Priory (1283) and to the Italian Gulielmus Durandus (1284).

Clockwork mechanisms were known in Europe by the early 1300s. Dante alluded in 1318 to the 'clock where one wheel moves so slowly but the other seems to fly round.' Six: years later we hear of a clock in Lincoln cathedral; Norwich Cathedral's dock with its astronomical dial, was made between 1322 and 1325 by Roger, Laurence and Robert de Stoke. By the 1370s every European cathedral had its clock. The dial of that at Wells is one of the very few that survive.

The complex astronomical timepiece with planetary motions begun by Richard of Wallingford at St Albans in 1327 though a marvel of the contemporary world was produced in the context of a growing tradition. However, Richard seems to have been an innovator, with his counting, striking train. Despite his genius, many English clocks were the work of European craftsmen and masters. In the 1350s there were Lombard clockmakers at Windsor: and in 1368 Flemings at Westminster. In 1336 the year of Wallingford's death, we find the first reference to a public clock with a counting striking train from St Milan (San Gottardo). By the end of the 14th century more or less every European city of any size had its own public clock. Few mechanisms either- from this or the following century survive.


There are clear contemporary indications of the expertise of late medieval metal workers and mechanicians. The cockerel automaton of the -First Strasbourg clock had individually articulated tail feathers. In 1388 a Polish MS. described a complicated mechanism [using triangular teeth in its cogging] to operate a manikin with articulated arms and fingers playing a keyboard. [1]

The famous Astrarium of Giovanni Dondi completed mid-14th century had been reconstructed from his working drawings in our own age and there were models at the Smithsonian Institution, Washington, and London's and Milan's Science Museums. Several other astralia were built in the 14th and 15th centuries, among them one by Regiomantanus of Nuremberg (ca. 1475) and one (ca. 1486) by Lorenzo dell a Vopaia of Florence.


Perhaps the first domestic clock could be identified as early as the reign of Philip IV the Fair (Philippe le Bel) of France who, some time between 1295 and 1300 paid for- a silver- (not iron) clock with two weights. Two inventions, the spring driven mechanism and the fusee made possible the development of fairly small and reasonably efficient domestic table clocks. From 1376 a Catalonian reference tells of a small clock with astrolabe dial, phases of the moon and three bells and apparently spring driven, and indicates a chamber clock. The fusee, a device to equalize the unwinding of a main spring, seemed to have been developed early in the 1400s. An illustration -from Keyser's Bellifortis (1405) illustrated a similar mechanism for assisting the bracing of a crossbow. A chamber clock made ca. 1425 and owned by Duke Philip the Good of Burgundy was spring driven as the speaker had demonstrated by stripping it down.

The well-known miniature illumination of Horloge de Sapience from ca. 1450 showed a small table clock with plated movement with its wheels in layers. This system meant that the maker could place the wheels of the mechanism precisely where he wanted them~ this in turn greatly facilitated miniaturization and thus (ultimately) led to watches.

The secretary thanked Mr Leopold for what had been an authoritatively precise even though wide-ranging survey of a subject of great interest to society members and, after discussion from the floor, closed the meeting at 5.55 p.m.