Full text provided by www.sciencedirect.com Endeavour Vol. 39 No. 1 ScienceDirect The role of the mechanical clock in medieval science Vı´ctor Pe´rez A´lvarez* Universidad de Valladolid, Facultad de Filosofı´a y Letras, Dep. Historia Antigua y Medieval, Pza. del Campus s/n, 47011 Valladolid Spain The invention and spread of the mechanical clock is a phenomenon involving many factors; telling time is just complex and multifaceted historical phenomenon. one and perhaps not even the most relevant factor. A Some of these facets, such as its social impact, have complete explanation of this phenomenon would exceed been widely studied, but their scientific dimensions have this paper’s aim, so we will focus on the mechanical clock’s often been dismissed. The mechanical clock was proba- scientific links before the invention of the pendulum in the bly born as a scientific instrument for driving a model of context of the so-called Scientific Revolution. the universe, and not only natural philosophers but also From the point of view of the history of technology, a kings, nobles and other members of the social elites mechanical clock is a device with at least three elements. showed an interest in clocks as scientific instruments. First, a clock requires a driving force to run the clockwork. Public clocks later spread a new way of telling time Hanging weights have been used for this purpose from the based on equal hours, laying the foundations for earliest history of the clock; but beginning in the first third changes in time consciousness that would accelerate of the 15th century, the spring was also used to drive small scientific thinking. domestic clocks.3 The second required element is an indi- What is a mechanical clock? The answer to this question cator showing the time information generated by the clock. depends on whom you ask. Today, most people consider it a Bells and dials have been the most common clock indica- time-telling instrument. Actually, it is a pillar of Western tors from the outset. The third essential feature is the society; we unconsciously use it numerous times every day, escapement, a mechanical device that stops the fall of but we usually do not reflect on the fact that if all clocks the weight at intervals and makes the clock run regularly. were to simultaneously fail, Western society would col- The escapement transforms the rotary motion of the lapse. Many historians, influenced by contemporary cul- wheels into an oscillating motion. Weight driven devices ture, have explained the origin of the mechanical clock and time indicators existed from late antiquity, but the through the assumed birth of a new necessity of time escapement only appeared in the last third of the 13th consciousness in 13th and 14th century Europe. Werner century and is the key technological novelty that allowed Sombart and Lewis Mumford, for example, found this new for the construction of the first mechanical clock. The necessity’s origin in strictly organized monastic life. Mum- escapement is the key element that distinguishes the ford asserted that the monastery was the natural context mechanical clock from other devices such as the clepsydra, for the invention of the mechanical clock.1 Other historians another time telling instrument in which water is both the have considered the advent of the clock to be a secular driving force and the escapement. phenomenon that was linked to a change in urban time consciousness. Jacques Le Goff developed the oft- referred Limitations on the measurement of time in the natural to notion of a struggle between ‘church time’, the old sciences religious time told by the bells, and ‘merchant’s time’, a From a history of science perspective, when the clock is new secular time measured by the newly invented mechan- considered a time device, it is linked with two elements: the ical clock, which the rising merchant class demanded.2 ‘modern time concept’ and ‘modern time reckoning’. The Social history perspectives such as these have been widely latter could be defined in opposition to ‘old time reckoning’, accepted and frequently used by historians. characterized by the separation of day and night with two Many of these ideas originate from misconceptions series of unequal hours for each. Various systems of mod- about what the mechanical clock was in the 14th and ern time reckoning have been used across the centuries, 15th centuries. Its birth and diffusion is a very complex but all of them use equal or equinoctial hours that a mechanical clock can easily measure. The oldest known *Tel.: +34 679 467 961. modern system is Italian reckoning, which counted twenty- 1 G. Dohrn-Van Rossum, History of the hour. Clocks and modern temporal orders, four hours from one sunset to the next. (Fig. 1) Another Chicago, The University of Chicago Press, 1996, p. 10. 2 J. Le Goff, Time, work and culture in the Middle Ages, Chicago, University of Chicago Press, 1980, p. 51–52. 3 E. Morpurgo, L´origine dell´orologio tascabile, Roma, Edizioni La Clessidra, 1954, p. Available online 20 March 2015 24. www.sciencedirect.com 0160-9327/ß 2015 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.endeavour.2015.02.004 64 Endeavour Vol. 39 No. 1 Fig. 2. Richard of Wallingford, abbot and scientific instrument maker, 14th century. British Library, MS Cotton Claudius E. IV, f. 201r. ß The British Library Board, UK. Fig. 1. ‘Italian clock’ in the Rialto Place, Venice, Italy. The reckoning of the twenty- inventions that changed mechanical clock history. Before four hour day begins at the sunset. these inventions, especially the pendulum, the mechanical ß Vı´ctor Pe´rez A´lvarez. clock was generally not suitable for scientific time mea- method is the half clock, which counted two twelve-hour surement. The case of Bernhard Walther is the exception series that began at midday and at midnight, no matter the that confirms the rule. length of day and night. Midday was the most common These limitations did not mean that the mechanical reference for adjusting clocks in Western Europe.4 clock was scientifically useless during this period or that The modern time concept can be defined as abstract, it had no connection with science. Some historians have mathematical and independent from nature; time is a hypothesized that astronomy encouraged the invention of magnitude that can be measured with the appropriate the mechanical clock.6 An important support for this hy- instrument. In the Middle Ages, the modern time concept pothesis is a commentary on the Sphere of Sacrobosco by took a prototypical form that was more theoretical than Robertus Anglicus published in 1941 by Lynn Thorndike.7 practical; it existed only in science and was told with In this well-known text, Anglicus expressed his desire to astronomical instruments, such as astrolabes or quad- have a self-moving mechanical machine to drive a model of rants. In 1484, Bernhard Walther was probably the first the universe, and he stated that scientific instrument known person to use a clock to measure modern time makers were searching for a way to make such a machine. accurately for scientific purposes. He used the clock during The commentary dates back to 1271, and it is been as- an observation of a Mercury transit across the sun, but sumed that the mechanical clock was invented after this he was forced to count the teeth of the hour wheel to know date; however, no certain information or concrete facts now the time in minutes. Three years after this event, he used substantiate that claim. Non-scientific motives, such the the clock again during an eclipse.5 Despite its mechanical construction of monastic alarms, could have also encour- limitations, his clock was acceptably accurate, though he aged the invention of the mechanical clock.8 We actually do used it only twice, as far as we know. not know exactly where, when and why the mechanical Walther’s effective use of the clock was exceptional for clock was invented, but the hypothesis that it was invented his day. 15th century clocks were generally bad time- to satisfy the scientific requirements of an exclusive schol- keepers, and they could not show minutes on their faces arly group is feasible.9 because of their inaccuracy. From the second half of the Some of the earliest clockmakers were also natural 16th century, there was a search for a reliably accurate philosophers or passed through a university. Richard of clock, for astronomy and for finding longitude at sea, that promoted progress in horological technology. Subsequent- 6 Derek J. De Solla Price, On the Origin of Clockwork, perpetual motion devices and ly, the cross-beat escapement, spiral spring, pendulum compass, Washington, Smithsonian Institution, United States National Museum, 1959, p. 86. and marine chronometer appeared, all great technical 7 L. Thorndike, ‘Invention of the mechanical clock about Ad 1271’, in Speculum, 16 (1941), p. 242–243. 4 8 G. Dohrn-Van Rossum, History of the hour. Clocks and modern temporal orders, L. Mumford, Technics and civilization, New York, Harcourt, Brace and Company, Chicago, The University of Chicago Press, 1996, p. 113–117. 1934, p. 13. 5 D.B. Beaver, ‘Bernard Walther: Innovator in astronomical observation’, in Jour- 9 J.D. North, God´s Clockmaker. Richard of Wallingford and the invention of time, nal for the History of Astronomy, 1 (1970), p. 40–41. London-New York, Hambledon and London, 2005, p. 160–166. www.sciencedirect.com  Endeavour Vol. 39 No. 1 65 are not conclusive evidence of the mechanical clock’s in- vention as a scientific instrument, but they show it had a connection with medieval science. Astronomical use of clocks out of the academic sphere Domestic mechanical clocks appeared in European royal courts in the mid-14th century at the latest. In the 15th century, clocks became commonplace and were present in the houses of aristocrats and other wealthy people. In general they were appreciated for being exclusive items and sometimes also for having astronomical indicators. Kings and nobles showed an interest in astronomy before the invention of the mechanical clock. A well-known exam- ple is Alphonse X ‘The Wise’, the 13th century Castilian king who promoted the Libros del saber de astronomia, an encyclopedic treatise on astronomy and astrology, which described some instruments, including clepsydrae, sun- dials and other types of non mechanical clocks13 (Fig. 4). In the 14th century Peter IV of Aragon was very interested in astronomy and he had astrolabes, quadrants, mechani- cal clocks and other instruments in his royal palaces. He paid various Jewish clockmakers for repairing and keeping his clocks in good working condition.14 Peter IV, in 1376, gave an outstanding astronomical clock to his daughter Leonor, who was married to the crown prince of Castile. He sent her a letter to describe it and explain how it worked. It Fig. 3. Astronomical clock of Padova, Italy. Originally built in the 14th century by had three bells, a moon indicator and a twenty-four hour Jacopo Dondi, Giovanni’s father. astrolabe face with three tympanums that covered the ß Vı´ctor Pe´rez A´lvarez. latitudes between 388 and 448, the range in which all territories of the kingdom of Aragon were located. The king told his daughter that she must select the correct Wallingford (c. 1292–1336), Giovanni Dondi (c. 1330–1388) tympanum depending on the latitude where the clock was and Jean Fusoris (c. 1365–1436) are still well-known me- used. The king also pointed out to his daughter that it dieval clockmakers who designed outstanding astronomi- would show her the day and night hours, the zodiac sign of cal clocks. The son of a blacksmith, Wallingford studied at the sun, the ascendant and other astronomical data for Oxford when he was a monk at Saint Albans Abbey (Fig. 2). astronomical or astrological purposes.15 He inherited his father’s metal working ability and ac- The king’s letter shows that this item was not a simple quired the astronomical knowledge to design the St. clock for telling time, but a complex instrument whose user Albans clock at Oxford.10 The son of a doctor and clock- should have basic astronomical knowledge to understand maker, Giovanni Dondi taught at the University of Padua its visual indicators. Peter IV’s letter to Leonor drew and designed a legendary astronomical clock that showed attention to the astronomical indicators of the clock, sug- the motions of the sun, the moon and the planets. The gesting he conceived of it as a scientific instrument rather clockwork was extremely complicated with elliptical and than a mere ornament. Leonor’s marriage to the Castilian irregular gears. This outstanding and legendary machine crown prince was intended as the seal of a peace treaty was probably destroyed at the end of the 15th century, but signed by Aragon and Castile, and the two were married it has never been forgotten.11 Jean Fusoris was a physi- the year before she received the clock. Because of this cian, mathematician, astronomer and scientific instru- political context, the clock can also be interpreted as a ment maker. He built the monumental clock for the diplomatic gift.16 In summary, this document shows that Bourges cathedral with astronomical indicators and a astronomy and astrology were of interest not only to aca- spherical clock driven by its own weight. He also worked demics and researchers and that the objects associated for the Duke of Burgundy and the Duke of Orleans among others12 (Fig. 3). 13 All these clockmakers are well-known historical figures A.J. Cardenas, A study and edition of the Royal Scriptorium manuscript of ‘El Libro del Saber de Astrologia’ by Alfonso X, el Sabio, Ann Arbor, Mi. University of in the history of science who constructed or designed clocks Wisconsin, 1974. for showing a scientific subject: the universe. Their works 14 C.F.C. Beeson, Perpignan 1356. The making of a Clock and Bell for the King´s Castle, London, The Antiquarian Horological Society, 1982, p. 2. 15 For an English translation of the description, see C.F.C. Beeson, ‘Perpignan 10 J.D. North, God´s Clockmaker. Richard of Wallingford and the invention of time, 1356 and the earliest clocks’, Antiquarian Horology, vol. 6 (June 1970), p. 408. See London-New York, Hambledon and London, 2005, p. 8 and 23. also C.F.C. Beeson, Perpignan 1356. The making of a Clock and Bell for the King´s 11 G. Brusa, L´arte dell´orologeria in Europa. Sette secoli di orologi meccanici, Busto Castle, London, The Antiquarian Horological Society, 1982, p. 6. 16 Arsizio, Bramante Editrice, 1978, p. 26. A study on the political significance of this clock: V. Perez Alvarez: ‘Mechanical 12 G. Brusa, L´arte dell´orologeria in Europa. Sette secoli di orologi meccanici, Busto clocks in the medieval Castilian royal court’, in Antiquarian Horology, vol. 34–4 Arsizio, Bramante Editrice, 1978, p. 33. (December 2013), p. 489–502. www.sciencedirect.com 66 Endeavour Vol. 39 No. 1 This excerpt can be translated as follows: A solar eclipse took place between twelve hours and one hour after midday, and the sun darkened, the stars appeared on the heavens, and it lasted very few moments. The former act mentions the word clock to define the hour type used for measuring the eclipse’s length. The time was not accurately measured in a modern sense, but we can verify the data with Calsky.18 This online application uses UTC, and Leon is located at about 58310 W; we have sub- tracted 22 min from the times given by Calsky to obtain the local time. For the 1421 event, the moon rose at 17:39 partially eclipsed; the totality was between 18:36 and 20:07; and the partial eclipse ended at 21:09 Both events Fig. 4. A mercury clepsydra with an astrolabe dial, from the Book on the Knowledge of astrology, by Alphonse X ‘The Wise’, 13th century. occurred and the calculations of Calsky agree with the data Universidad Complutense de Madrid, BH, MSS, 156, f. 194v. ß Universidad from the chapter acts, so the times were well registered. Complutense de Madrid, Spain. The Castilian term relox, and its different forms, derive from the Latin term horologium, a word which preceded the invention of the mechanical clock. In the 14th and 15th centuries an horologium or a relox could mean a calendar, with them served also as prestige objects for social distinc- an astrolabe, a quadrant, a clepsydra, a mechanical clock, tion. just a bell, or any other instrument for time telling. So, Mechanical clocks and clock hours were occasionally when this term is found in a medieval document, it does not used to register significant astronomical events such always refer to a mechanical clock. The mechanical clock eclipses. As long as these events were believed to influence spread modern time reckoning across Europe, and pushed human life, astronomers and many others were interested the construction of scales of clock hours on old instruments in them. These events can be found in chronicles, annals like astrolabs or quadrants. So, a clock time reference does and many different archival sources. not necessarily imply that a mechanical clock was used, but The chapter acts of Leon Cathedral have two interesting only that modern time reckoning has been introduced. In registers of astrological events. Leon is a historical city in the chapter acts of Leon Cathedral the length of the lunar northwestern Spain. Its gothic cathedral preserves excel- eclipse is expressed in horas de relox, that is in ‘clock lent archival collections, including the chapter act series hours.’ This is synonymous with ‘equinoctial hours’, and that begin in the early 15th century. We can find many in contrast to canonical hours, which were more frequently daily time references in these acts, mostly canonical hours, used in Leon’s chapter acts. Here there is no reference to a middays, sunrises and sunsets, but there are also two particular mechanical clock, but to the type of hours shown clock-time references in this period, both recording by mechanical clocks. The times of the beginning and the eclipses. The first one describes the lunar eclipse of 17 Feb- ending of both events are not explicitly defined as ‘clock ruary 1421: hours’ because, as the reckoning begins at midday, it is Este dia, a las seys horas despues de mediodia, obvious they are equinoctial clock hours. comenc¸o a oscurecer la luna, e duro el eclipssy fasta Now the question is whether a mechanical clock or any las siete horas e media e mas tienpo en tanto que duro other instrument was used to find the times of these el eclipssy dos horas de rrellox17 eclipses, particularly the earliest one (Fig. 5). The oldest evidence of a mechanical clock’s existence in the Cathedral of Leon dates back to 1424, three years after the lunar This excerpt can be translated as follows: eclipse. This evidence appears in another chapter act about a pension payment to the clock keeper because he had This day, six hours after midday, the moon began to retired after working in the cathedral for many years.19 darken, and the eclipse continued until half past seven This mention almost certainly proves that a mechanical or later, so the eclipse lasted two clock hours. clock was running during the 1421 lunar eclipse. Because of the ambiguity of the term relox at this time, we cannot The second one is the total solar eclipse of 29 July 1478, confirm that the cathedral’s mechanical clock was used to described as follows: record the eclipse’s duration, but it likely was. Regardless, the fact that equal hours and modern time reckoning are Ovo eclinsi en el sol entre las doze oras e la una used only twice in the 15th century Leon cathedral chapter despues de medio dı´a, e oscureciose el sol e parecieron acts and both instances record meaningful astronomical las estrellas en el cielo, e duro por poco espacio. events shows a connection between the mechanical clock and astronomy, a scientific discipline. 18 http://www.calsky.com/ September 23, 2013. 17 19 Archive of Leon´s Cathedral, Chapter Acts, N. 9798. 1421, February, 17. Archive of Leon´s Cathedral, Chapter Acts, N. 9800, 1424, August, 4. www.sciencedirect.com  Endeavour Vol. 39 No. 1 67 This excerpt can be translated as follows: Saturday night, the 3rd day of September, at the eighth hour, the year 1457, there was a great lunar eclipse, and one half of the moon became very dark and the other half as she has been. And at the tenth hour of the night she began to be illuminated and at the twelfth hour of the night she became completely illuminated; she was thus eclipsed for four hours. According to Calsky, the eclipse occurred between 20:00 and 23:30, and the totality occurred between 21:04 and 22:15 in local time. Once again, these Calsky data confirm that the eclipse occurred and was correctly measured within the reliability range for that time. Only the descrip- tion of the eclipse type seems incorrect here; according to Calsky, it was a total eclipse, but Garci Sanchez suggests it was partial. Just the hour length is noted in the other two lunar eclipse records. In these Anales, clock time is used to date other facts, for example, to register a crown prince’s birth: Miercoles a la una hora despues de la medianoche, 15 dias de noviembre deste an˜o de 1453, nascio el infante don Alfonso. . . This excerpt can be translated as follows: Wednesday at one hour after midnight, 15 days into November of this year of 1453, the prince don Alfonso Fig. 5. The clock tower of the Leon Cathedral, Spain, 15th century. ß Vı´ctor Pe´rez A´lvarez. was born. . . Similar uses of clock time can be found in other chroni- It was very common to make note of the birth hour of cles or annals, for example, in the Anales de Garci Sanchez, future kings, at least in the 15th century. The interest in written in Seville after 1469, the final record-year of this accurately knowing the birth moment can be potentially registry.20 The author worked for Seville’s city council, and explained by the desire to generate his horoscope, but this his presence is recorded there in November 1443.21 The record also possibly suggests the widespread use of the Anales explored a wide range of issues, mostly relating to mechanical clock and modern time consciousness. Garci Seville, but some episodes occured in Cuenca and different Sanchez makes note of his coronation ceremony fourteen Castilian locales (for those relating to the king). Some facts years later at one o’clock at night, his birth hour, probably were accurately dated with the full date and the time in to emphasize the ceremony’s legality. clock hours—and sometimes in canonical hours. One chronicled event occured in 1432, and the others dated Conclusions from 1453 to 1469 during the author’s lifetime. There are From its earliest moments, the mechanical clock has been a no earlier events registered with clock hours, probably prestige object. It was a self-moving machine that captured because they were not often used previously. Garci San- people’s attention in the 14th and 15th centuries. Clocks chez only gave accurate dates with hours for meteorologi- were very unusual and so expensive that only wealthy cal, astrological and political events. Three astrological institutions and affluent people could afford them. As a events were lunar eclipses, but only the first eclipse record time-telling instrument, they played increasingly impor- included its start and end in clock hours: tant roles in the organization of urban daily life and in activity coordination. At the same time that it was becom- Sabado en la noche, 3 dias de septiembre, a hora de las ing a common urban accessory, the clock was gradually ocho, an˜o de 1457, hizo grande eclipse la luna, y se torno used to institute time regulations. The clock determined fasta la mitad muy negra, y de la otra mitad como ha de the opening and closing of markets and city doors, the estar. Y a las diez horas de la noche torno a esclarecerse, summons to city council, deadlines for auctions, and so on. y a las doce horas de la dicha noche esclarecio´ toda; y Europe’s introduction of the mechanical clock is a ansy estuvo eclipsada quatro horas.22 complex issue, and the historiography has explored these 20 J.M. Carriazo: ‘Anales de Garci Sa´nchez, jurado de Sevilla’, in Anales de la roles in a way that often undervalues or even denies its Universidad Hispalense, 14 (1953), p. 3–63. relationship to science. From our perspective, systemati- 21 J.M. Carrizao: ‘El Ape´ndice, referido a Cuenca, de los «Anales de Garci Sa´nchez, cally and accurately measuring every quantifiable param- jurado de Sevilla»’, in En la Espan˜a Medieval, 1 (1980), p. 60. 22 J.M. Carriazo: ‘Anales de Garci Sa´nchez, jurado de Sevilla’, in Anales de la eter to their smallest possible units or finest degrees is an Universidad Hispalense, 14 (1953), p. 176. exemplar of scientific practice. Thus, when we know that www.sciencedirect.com 68 Endeavour Vol. 39 No. 1 medieval mechanical clocks were so inaccurate that they sometimes voluntarily to satisfy personal interests or per- could not show minutes, we are in danger of assuming haps for social purposes. Others did not have these inter- clocks could not have served a scientific function prior to ests, but they lived in cities and towns with public clocks. the 17th century. In medieval thought reason played a Originally, these new self-moving machines may have more important role than the observation of nature; medi- amused urbanites, but people probably did not pay atten- eval science was in general more qualitative than quanti- tion to the continuous time indication until clock-time tative and more symbolic than current scientific thought, regulations were established for daily activities. When so the mechanical clock had more significance as a symbol ordinary people were compelled to use clocks, a long tran- than as a time measurer. Scientific thinking did not exist in sition process toward a more abstract concept of time the Middle Ages as it does today, but medieval men also began. This shift is the primary achievement of the me- wished to increase their knowledge of the natural world chanical clock and its main conceptual novelty, as its role and the created universe. They used different methods to as a model of the universe had been played by clepsydrae in acquire this knowledge and generated valid conclusions previous centuries. The mechanical clock was likely born to that laid the foundations for modern science. meet scientific needs, but when it was put in the service of a The strong scholarly commitment to science was obvi- wide range of people, it then promoted and popularized ous, but other people approached science in different ways, scientific thinking. www.sciencedirect.com