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You may copy it, give it away or +re-use it under the terms of the Project Gutenberg License included +with this eBook or online at www.gutenberg.org + + +Title: On the Origin of Clockwork, Perpetual Motion Devices, and the Compass + +Author: Derek J. de Solla Price + +Release Date: September 16, 2009 [EBook #30001] + +Language: English + +Character set encoding: UTF-8 + +*** START OF THIS PROJECT GUTENBERG EBOOK ON THE ORIGIN OF CLOCKWORK *** + + + + +Produced by Chris Curnow, Turgut Dincer, Joseph Cooper and +the Online Distributed Proofreading Team at +https://www.pgdp.net. + + + + + + + +--------------------------------------------------------------+ + | This e-text includes characters that require UTF-8 | + | (Unicode) file encoding: | + | | + | ḍ, ā, ḥ, ȧ, ī | + | | + | If any of these characters do not display properly--in | + | particular, if the dots do not appear under the letters | + | make sure your text reader’s “character set” or “file | + | encoding” is set to Unicode (UTF-8). You may also need to | + | change the default font. Depending on available fonts, some | + | tables may not line up vertically. | + +--------------------------------------------------------------+ + + + + + CONTRIBUTIONS FROM + + THE MUSEUM OF HISTORY AND TECHNOLOGY: + + PAPER 6 + + + + + ON THE ORIGIN OF CLOCKWORK, + + PERPETUAL MOTION DEVICES AND THE COMPASS + + _Derek J. de Solla Price_ + + + + POWER AND MOTION GEARING 83 + + MECHANICAL CLOCKS 84 + + MECHANIZED ASTRONOMICAL MODELS 88 + + PERPETUAL MOTION AND THE CLOCK BEFORE DE DONDI 108 + + THE MAGNETIC COMPASS AS A FELLOW-TRAVELER FROM CHINA 110 + + + + + _ON THE ORIGIN OF CLOCKWORK,_ + + _PERPETUAL MOTION DEVICES_ + + _AND THE COMPASS_ + + _By Derek J. de Solla Price_ + + +_Ancestor of the mechanical clock has been thought by some to be the +sundial. Actually these devices represent two different approaches to +the problem of time-keeping. True ancestor of the clock is to be found +among the highly complex astronomical machines which man has been +building since Hellenic times to illustrate the relative motions of the +heavenly bodies._ + +_This study--its findings will be used in preparing the Museum's new +hall on the history of time-keeping--traces this ancestry back through +2,000 years of history on three continents._ + +THE AUTHOR: _Derek J. de Solla Price wrote this paper while serving as +consultant to the Museum of History and Technology of the Smithsonian +Institution's United States National Museum._ + + In each successive age this construction, having become + lost, is, by the Sun's favour, again revealed to some one + or other at his pleasure. (_Sūrya Siddhānta_, ed. + Burgess, xiii, 18-19.) + + +THE HISTORIES of the mechanical clock and the magnetic compass must be +accounted amongst the most tortured of all our efforts to understand the +origins of man's important inventions. Ignorance has too often been +replaced by conjecture, and conjecture by misquotation and the false +authority of "common knowledge" engendered by the repetition of +legendary histories from one generation of textbooks to the next. In +what follows, I can only hope that the adding of a strong new trail and +the eradication of several false and weaker ones will lead us nearer to +a balanced and integrated understanding of medieval invention and the +intercultural transmission of ideas. + +For the mechanical clock, perhaps the greatest hindrance has been its +treatment within a self-contained "history of time measurement" in which +sundials, water-clocks and similar devices assume the natural role of +ancestors to the weight-driven escapement clock in the early 14th +century.[1] This view must presume that a generally sophisticated +knowledge of gearing antedates the invention of the clock and extends +back to the Classical period of Hero and Vitruvius and such authors +well-known for their mechanical ingenuities. + +Furthermore, even if one admits the use of clocklike gearing before the +existence of the clock, it is still necessary to look for the +independent inventions of the weight-drive and of the mechanical +escapement. The first of these may seem comparatively trivial; anyone +familiar with the raising of heavy loads by means of ropes and pulley +could surely recognize the possibility of using such an arrangement in +reverse as a source of steady power. Nevertheless, the use of this +device is not recorded before its association with hydraulic and +perpetual motion machines in the manuscripts of Riḍwān, _ca._ 1200, +and its use in a clock using such a perpetual motion wheel (mercury +filled) as a clock escapement, in the astronomical codices of Alfonso +the Wise, King of Castile, _ca._ 1272. + +The second invention, that of the mechanical escapement, has presented +one of the most tantalizing of problems. Without doubt, the crown and +foliot type of escapement appears to be the first complicated mechanical +invention known to the European Middle Ages; it heralds our whole age of +machine-making. Yet no trace has been found either of a steady evolution +of such escapements or of their invention in Europe, though the +astronomical clock powered by a water wheel and governed by an +escapement-like device had been elaborated in China for several +centuries before the first appearance of our clocks. We must now +rehearse a revised story of the origin of the clock as it has been +suggested by recent researches on the history of gearing and on Chinese +and other astronomical machines. After this we shall for the first time +present evidence to show that this story is curiously related to that of +the _Perpetuum Mobile_, one of the great chimeras of science, that came +from its medieval origin to play an important part in more recent +developments of energetics and the foundations of thermodynamics.[2] It +is a curious mixture, all the more so because, tangled inextricably in +it, we shall find the most important and earliest references to the use +of the magnetic compass in the West. It seems that in revising the +histories of clockwork and the magnetic compass, these considerations +of perpetual motion devices may provide some much needed evidence. + +[Illustration: Figure 1.--FRAMEWORK STRUCTURE OF THE ASTRONOMICAL CLOCK +of Giovanni de Dondi of Padua, A.D. 1364.] + + + + +Power and Motion Gearing + +It may be readily accepted that the use of toothed wheels to transmit +power or turn it through an angle was widespread in all cultures several +centuries before the beginning of our era. Certainly, in classical times +they were already familiar to Archimedes (born 287 B.C.),[3] and in +China actual examples of wheels and moulds for wheels dating from the +4th century B.C. have been preserved.[4] It might be remarked that +these "machine" gear wheels are characterized by having a "round number" +of teeth (examples with 16, 24 and 40 teeth are known) and a shank with +a square hole which fits without turning on a squared shaft. Another +remarkable feature in these early gears is the use of ratchet-shaped +teeth, sometimes even twisted helically so that the gears resemble worms +intermeshing on parallel axles.[5] The existence of windmills and +watermills testifies to the general familiarity, from classical times +and through the middle ages, with the use of gears to turn power through +a right angle. + +[Illustration: Figure 2.--ASTRONOMICAL CLOCK of de Dondi, showing +gearing on the dial for Mercury and escapement crown wheel. Each of the +seven side walls of the structure shown in figure 1 was fitted with a +dial.] + +Granted, then, this use of gears, one must guard against any conclusion +that the fine-mechanical use of gears to provide special ratios of +angular movement was similarly general and widespread. It is customary +to adduce here the evidence of the hodometer (taximeter) described by +Vitruvius (1st century B.C.) and by Hero of Alexandria (1st century +A.D.) and the ingenious automata also described by this latter author +and his Islamic followers.[6] One may also cite the use of the reduction +gear chain in power machinery as used in the geared windlass of +Archimedes and Hero. + +Unfortunately, even the most complex automata described by Hero and by +such authors as Riḍwān contain gearing in no more extensive context +than as a means of transmitting action around a right angle. As for the +windlass and hodometer, they do, it is true, contain whole series of +gears used in steps as a reduction mechanism, usually for an +extraordinarily high ratio, but here the technical details are so +etherial that one must doubt whether such devices were actually realized +in practice. Thus Vitruvius writes of a wheel 4 feet in diameter and +having 400 teeth being turned by a 1-toothed pinion on a cart axle, but +it is very doubtful whether such small teeth, necessarily separated by +about 3/8 inch, would have the requisite ruggedness. Again, Hero +mentions a wheel of 30 teeth which, because of imperfections, might need +only 20 turns of a single helix worm to turn it! Such statements behove +caution and one must consider whether we have been misled by the +16th- and 17th-century editions of these authors, containing +reconstructions now often cited as authoritative but then serving as +working diagrams for practical use in that age when the clock was +already a familiar and complex mechanism. At all events, even if one +admits without substantial evidence that such gear reduction devices +were familiar from Hellenistic times onwards, they can hardly serve as +more than very distant ancestors of the earliest mechanical clocks. + + + + +Mechanical Clocks + +Before proceeding to a discussion of the controversial evidence which +may be used to bridge this gap between the first use of gears and the +fully-developed mechanical clock we must examine the other side of this +gap. Recent research on the history of early mechanical clocks has +demonstrated certain peculiarities most relevant to our present +argument. + + +THE EUROPEAN TRADITION + +If one is to establish a _terminus ante quem_ for the appearance of the +mechanical clock in Europe, it would appear that 1364 is a most +reasonable date. At that time we have the very full mechanical and +historical material concerning the horological masterpiece built by +Giovanni de Dondi of Padua,[7] and probably started as early as 1348. It +might well be possible to set a date a few decades earlier, but in +general as one proceeds backwards from this point, the evidence becomes +increasingly fragmentary and uncertain. The greatest source of doubt +arises from the confusion between sundials, water-clocks, hand-struck +time bells, and mechanical clocks, all of which are covered by the term +_horologium_ and its vernacular equivalents. + +Temporarily postponing the consideration of evidence prior to _ca._ +1350, we may take Giovanni de Dondi as a starting point and trace a +virtually unbroken lineage from his time to the present day. One may +follow the spread of clocks through Europe, from large towns to small +ones, from the richer cathedrals and abbeys to the less wealthy +churches.[8] There is the transition from the tower clocks--showpieces +of great institutions--to the simple chamber clock designed for domestic +use and to the smaller portable clocks and still smaller and more +portable pocket watches. In mechanical refinement a similar continuity +may be noted, so that one sees the cumulative effect of the introduction +of the spring drive (_ca._ 1475), pendulum control (_ca._ 1650), and the +anchor escapement (_ca._ 1680). The transition from de Dondi to the +modern chronometer is indeed basically continuous, and though much +research needs to be done on special topics, it has an historical unity +and seems to conform for the most part to the general pattern of steady +mechanical improvement found elsewhere in the history of technology. + +[Illustration: Figure 3.--GERMAN WALL CLOCK, PROBABLY ABOUT 1450, +showing the degeneration in complexity from that of de Dondi's clock.] + +Most remarkable however is the earliest period of this seemingly steady +evolution. Side by side with the advances made in the earliest period +extending for less than two centuries from the time of de Dondi one may +see a spectacular process of degeneration or devolution. Not only is de +Dondi's the earliest clock of which we have a full and trustworthy +account, it is also far more complicated than any other (see figs. 1, 2) +until comparatively modern times! Moreover, it was not an exceptional +freak. There were others like it, and one cannot therefore reject as +accidental this process of degeneration that occurs at the very +beginning of the certain history of the mechanical clock in Europe. + +On the basis of such evidence I have suggested elsewhere[9] that the +clock is "nought but a fallen angel from the world of astronomy." The +first great clocks of medieval Europe were designed as astronomical +showpieces, full of complicated gearing and dials to show the motions of +the Sun, Moon and planets, to exhibit eclipses, and to carry through the +involved computations of the ecclesiastical calendar. As such they were +comparable to the orreries of the 18th century and to modern +planetariums; that they also showed the time and rang it on bells was +almost incidental to their main function. One must not neglect, too, +that it was in their glorification of the rationality of the cosmos that +they had their greatest effect. Through milleniums of civilization, +man's understanding of celestial phenomena had been the very pinnacle of +his intellect, and then as now popular exhibition of this sort was just +as necessary, as striking, and as impressive. One does not have to go +far to see how the paraphernalia of these early great astronomical +clocks had great influence on philosophers and theologians and on poets +such as Dante. + +It is the thesis of this part of my argument that the ordinary +time-telling clock is no affiliate of the other simple time-telling +devices such as sundials, sand glasses and the elementary water clocks. +Rather it should be considered as a degenerate branch from the main stem +of mechanized astronomical devices (I shall call them protoclocks), a +stem which can boast a continuous history filling the gap between the +appearance of simple gearing and the complications of de Dondi. We shall +return to the discussion of this main stem after analyzing the very +recently discovered parallel stem from medieval China, which reproduced +the same evolution of mechanized astronomical devices and incidental +time telling. Of the greatest significance, this stem reveals the +crucial independent invention of a mechanical escapement, a feature not +found in the European stem in spite of centuries of intensive historical +research and effort. + + +THE CHINESE TRADITION + +For this section I am privileged to draw upon a thrilling research +project carried out in 1956 at the University of Cambridge by a team +consisting of Dr. Joseph Needham, Dr. Wang Ling, and myself.[10] In the +course of this work we translated and commented on a series of texts +most of which had not hitherto been made available in a Western tongue +and, though well known in China, had not been recognized as important +for their horological content. The key text with which we started was +the "Hsin I Hsiang Fa Yao," or "New Design for a (mechanized) Armillary +(sphere) and (celestial) Globe," written by Su Sung in A.D. 1090. The +very full historical and technical description in this text enabled us +to establish a glossary and basic understanding of the mechanism that +later enabled us to interpret a whole series of similar, though less +extensive texts, giving a history of prior development of such devices +going back to the introduction of this type of escapement by I-Hsing and +Liang Ling-tsan, in A.D. 725, and to what seems to be the original of +all these Chinese astronomical machines, that built by Chang Hêng _ca._ +A.D. 130. Filling the gaps between these landmarks are several other +similar texts, giving ample evidence that the Chinese development is +continuous and, at least from Chang Hêng onwards, largely independent of +any transmissions from the West. + +So far as we can see, the beginning of the chain in China (as indeed in +the West) was the making of simple static models of the celestial +sphere. An armillary sphere was used to represent the chief imaginary +circles (_e.g._, equator, ecliptic, meridians, etc.), or a solid +celestial globe on which such circles could be drawn, together with the +constellations of the fixed stars. The whole apparatus was then mounted +so that it was free to revolve about its polar axis and another ring or +a casing was added, external and fixed, to represent the horizon that +provided a datum for the rising and setting of the Sun and the stars. + +In the next stage, reached very soon after this, the rotation of the +model was arranged to proceed automatically instead of by hand. This was +done, we believe, by using a slowly revolving wheel powered by dripping +water and turning the model through a reduction mechanism, probably +involving gears or, more reasonably, a single large gear turned by a +trip lever. It did not matter much that the time-keeping properties were +poor in the long run; the model moved "by itself" and the great wonder +was that it agreed with the observed heavens "like the two halves of a +tally." + +In the next, and essential, stage the turning of the water wheel was +regulated by an "escapement" mechanism consisting of a weighbridge and +trip levers so arranged that the wheel was held in check, scoop by +scoop, while each scoop was filled by the dripping water, then released +by the weighbridge and allowed to rotate until checked again by the +trip-lever arrangement. Its action was similar to that of the anchor +escapement, though its period of repose was much longer than its period +of motion and, of course, its time-keeping properties were controlled not +only by the mechanics of the device but also by the rate of flow of the +dripping water. + +The Chinese escapement may justifiably be regarded as a missing link, +just halfway between the elementary clepsydra with its steady flow of +water and the mechanical escapement in which time is counted by chopping +its flow into cycles of action, repeated indefinitely and counted by a +cumulating device. With its characteristic of saving up energy for a +considerable period (about 15 minutes) before letting it go in one +powerful action, the Chinese escapement was particularly suited to the +driving of jackwork and other demonstration devices requiring much +energy but only intermittent activity. + +In its final form, as built by Su Sung after many trials and +improvements, the Chinese "astronomical clock-tower" must have been a +most impressive object. It had the form of a tower about 30 feet high, +surmounted by an observation platform covered with a light roof (see +fig. 4). On the platform was an armillary sphere designed for observing +the heavens. It was turned by the clockwork so as to follow the diurnal +rotation and thus avoid the distressing computations caused by the +change of coordinates necessary when fixed alt-azimuth instruments were +used. Below the platform was an enclosed chamber containing the +automatically rotated celestial globe which so wonderfully agreed with +the heavens. Below this, on the front of the tower was a miniature +pagoda with five tiers; on each tier was a doorway through which, at due +moment, appeared jacks who rang bells, clanged gongs, beat drums, and +held tablets to announce the arrival of each hour, each quarter (they +used 100 of them to the day) and each watch of the night. Within the +tower was concealed the mechanism; it consisted mainly of a central +vertical shaft providing power for the sphere, globe, and jackwheels, +and a horizontal shaft geared to the vertical one and carrying the great +water wheel which seemed to set itself magically in motion at every +quarter. In addition to all this were the levers of the escapement +mechanism and a pair of norias by which, once each day, the water used +was pumped from a sump at the bottom to a reservoir at the top, whence +it descended to work the wheel by means of a constant level tank and +several channels. + +There were many offshoots and developments of this main stem of Chinese +horology. We are told, for example, that often mercury and occasionally +sand were used to replace the water, which frequently froze in winter in +spite of the application of lighted braziers to the interior of the +machines. Then again, the astronomical models and the jackwork were +themselves subject to gradual improvement: at the time of I-Hsing, for +example, special attention was paid to the demarcation of ecliptic as +well as the normal equatorial coordinates; this was clearly an influx +from Hellenistic-Islamic astronomy, in which the relatively +sophisticated planetary mathematics had forced this change not otherwise +noted in China. + +By the time of the Jesuits, this current of Chinese horology, long since +utterly destroyed by the perils of wars, storms, and governmental +reforms, had quite been forgotten. Matteo Ricci's clocks, those gifts +that aroused so much more interest than European theological teachings, +were obviously something quite new to the 16th-century Chinese scholars; +so much so that they were dubbed with a quite new name, "self-sounding +bells," a direct translation of the word "clock" (_glokke_). In view of +the fact that the medieval Chinese escapement may have been the basis of +European horology, it is a curious twist of fate that the high regard of +the Chinese for European clocks should have prompted them to open their +doors, previously so carefully and for so long kept closed against the +foreign barbarians. + +[Illustration: Figure 4.--ASTRONOMICAL CLOCK TOWER OF SU SUNG in +K'ai-feng, _ca._ A.D. 1090, from an original drawing by John +Christiansen. (_Courtesy of Cambridge University Press._)] + + + + +Mechanized Astronomical Models + +Now that we have seen the manner in which mechanized astronomical models +developed in China, we can detect a similar line running from +Hellenistic time, through India and Islam to the medieval Europe that +inherited their learning. There are many differences, notably because of +the especial development of that peculiar characteristic of the West, +mathematical astronomy, conditioned by the almost accidental conflux of +Babylonian arithmetical methods with those of Greek geometry. However, +the lines are surprisingly similar, with the exception only of the +crucial invention of the escapement, a feature which seems to be +replaced by the influx of ideas connected with perpetual motion wheels. + + +HELLENISTIC PERIOD + +Most interesting and frequently cited is the bronze planetarium said to +have been made by Archimedes and described in a tantalisingly +fragmentary fashion by Cicero and by later authors. Because of its +importance as a prototype, we give the most relevant passages in +full.[11] + +Cicero's descriptions of Archimedes' planetarium are (italics supplied): + + Gaius Sulpicius Gallus ... at a time when ... he happened + to be at the house of Marcus Marcellus, his colleague in + the consulship [166 B.C.], ordered the celestial globe to + be brought out which the grandfather of Marcellus had + carried off from Syracuse, when that very rich and + beautiful city was taken [212 B.C.].... Though I had heard + this globe (sphaerae) mentioned quite frequently on + account of the fame of Archimedes, when I saw it I did not + particularly admire it; for that other celestial globe, + also constructed by Archimedes, which the same Marcellus + placed in the temple of Virtue, is more beautiful as well + as more widely known among the people. But when Gallus + began to give a very learned explanation of the device, I + concluded that the famous Sicilian had been endowed with + greater genius than one would imagine possible for human + being to possess. For Gallus told us that the other kind + of celestial globe, which was solid and contained no + hollow space, was a very early invention, the first one of + that kind having been constructed by Thales of Miletus, + and later marked by Eudoxus of Cnidus--a disciple of + Plato, it was claimed--with constellations and stars which + are fixed in the sky. He also said that many years later + Aratus ... had described it in verse.... But this newer + kind of globe, he said, on which were delineated the + motions of the sun and moon and of those five stars which + are called wanderers, or, as we might say, rovers + [_i. e._, the five planets], contained more than could be + shown on the solid globe, and the invention of Archimedes + deserved special admiration because he had thought out a + way to represent accurately by a single device for turning + the globe, those various and divergent movements with + their different rates of speed. And when Gallus moved + [_i.e._, set in motion] the globe, it was actually true + that the moon was always as many revolutions behind the + sun on the _bronze_ contrivance as would agree with the + number of days it was behind in the sky. Thus the same + eclipse of the sun happened on the globe as would actually + happen, and the moon came to the point where the shadow of + the earth was at the very time when the sun (appeared?) + out of the region ... [several pages are missing in the + manuscript; there is only one]. + + _De republica_, I, xiv (21-22), Keyes' translation. + + When Archimedes put together in a globe the movements of + the moon, sun and five wandering [planets], he brought + about the same effect as that which the god of Plato did + in the Timaeus when he made the world, so that one + revolution produced dissimilar movements of delay and + acceleration. + + _Tusculanae disputationes_, I, 63. + +Later descriptions from Ovid, Lactantius, Claudian, Sextus Empiricus, +and Pappus, respectively, are (italics supplied): + + There stands a globe suspended by a Syracusan's skill in + an enclosed bronze [frame, or sphere--or perhaps, in + enclosed air], a small image of the immense vault [of + heaven]; and the earth is equally distant from the top and + bottom; that is brought about by its [_i. e._, the outer + bronze globe's] round form. The form of the temple [of + Vesta] is similar.... + + Ovid, _Fasti_ (1st century, A.D.), VI, 277-280, + Frazer's translation. + + The Sicilian Archimedes, was able to make a reproduction + and model of the world in concave _brass_ (concavo aere + similitudinem mundi ac figuram); in it he so arranged the + _sun_ and _moon_ and resembling the celestial revolutions + (caelestibus similes conversionibus); and while it + revolved it exhibited not only the accession and recession + of the sun and the waxing and waning of the moon + (incrementa deminutionesque lunae), but also the unequal + _courses of the stars_, whether fixed or wandering. + + Lactantius, _Institutiones divinae_ (4th century, A.D.), + II, 5, 18. + + Archimedes' sphere. When Jove looked down and saw the + heavens figured in a sphere of _glass_, he laughed and + said to the other gods: "Has the power of mortal effort + gone so far? Is my handiwork now mimicked in a fragile + globe?" An old man of Syracuse had imitated on earth the + laws of the heavens, the order of nature, and the + ordinances of the gods. Some hidden influence within the + sphere directs the various courses of the _stars_ and + actuates the lifelike mass with definite motions. A false + _zodiac_ runs through a year of its own and a toy _moon_ + waxes and wanes month by month. Now bold invention + rejoices to make its own heaven revolve and sets the + _stars_ [planets?] in motion by human wit.... + + Claudian, _Carmina minora_ (_ca._ A.D. 400), LI (LXVIII), + Platnaure's translation. + + The things that move by themselves are more wonderful than + those which do not. At any rate, when we behold an + Archimedean sphere in which the sun and the rest of the + stars move, we are immensely impressed by it, not by Zeus + because we are amazed at the _wood_, or at the movements + of these [bodies], but by the devices and causes of the + movements. + + Sextus Empiricus, _Adversus mathematicos_ (3rd century, + A.D.), IX, 115, Epps' translation. + + Mechanics understand the making of spheres and know how to + produce a model of the heavens (with the courses of the + stars moving in circles?) by mean of equal and circular + motions of _water_, and Archimedes the Syracusan, + according to some, knows the cause and reasons for all of + these. + + Pappus (3rd century, A.D.), _Works_ (Hultsch edition), + VIII, 2, Epps' translation. + +A similar arrangement seems to be indicated in another mechanized globe, +also mentioned by Cicero and said to have been made by Posidonius: + + But if anyone brought to Scythia or Britain the globe + (sphaeram) which our friend Posidonius [of Apameia, the + Stoic philosopher] recently made, in which each revolution + produced the same (movements) of the _sun_ and _moon_ and + _five_ wandering stars as is produced in the sky each day + and night, who would doubt that it was by exertion of + reason?... Yet doubters ... think that Archimedes showed + more knowledge in producing movements by revolutions of a + globe than nature (does) in effecting them though the copy + is so infinitely inferior to the original.... + + _De natura deorum_, II, xxxiv-xxxv (88), + Yonge's translation. + +In spite of the lack of sufficient technical details in any case, these +mechanized globe models, with or without geared planetary indicators +(which would make them highly complex machines), bear a striking +resemblance to the earliest Chinese device described by Chang Hêng. One +must not reject the possibility that transmission from Greece or Rome +could have reached the East by the beginning of the 2nd century, A.D., +when he was working. It is an interesting question, but even if such +contact actually occurred, very soon afterwards, as we shall see, the +western and eastern lines of evolution parted company and evolved so far +as can be seen, quite independently until at least the 12th century. + +The next Hellenistic source of which we must take note is a fragmentary +and almost unintelligible chapter in the works of Hero of Alexandria. +Alone and unconnected with his other chapters this describes a model +which seems to be static, in direct contrast to all other devices which +move by pneumatic and hydrostatic pressures; it may well be conjectured +that in its original form this chapter described a mechanized rather +than a static globe: + + The World represented in the Centre of the Universe: The + construction of a transparent globe containing air and + liquid, and also of a smaller globe, in the centre, in + imitation of the World. Two hemispheres of glass are made; + one of them is covered with a plate of bronze, in the + middle of which is a round hole. To fit this hole a light + ball, of small size, is constructed, and thrown into the + water contained in the other hemisphere: the covered + hemisphere is next applied to this, and, a certain + quantity of the liquid having been removed from the water, + the intermediate space will contain the ball; thus by the + application of the second hemisphere what was proposed is + accomplished. + + _Pneumatics_, XLVI, Woodcroft's translation. + +It will be noted that these earliest literary references are concerned +with pictorial, 3-dimensional models of the universe, moved perhaps by +hand, perhaps by waterpower; there is no evidence that they contained +complicated trains of gears, and in the absence of this we may incline +to the view that in at least the earliest such models, gearing was not +used. + +The next developments were concerned on the one hand with increasing the +mathematical sophistication of the model, on the other hand with its +mechanical complexity. In both cases we are most fortunate in having +archaeological evidence which far exceeds any literary sources. + +The mathematical process of mapping a sphere onto a plane surface by +stereographic projection was introduced by Hipparchus and had much +influence on astronomical techniques and instruments thereafter. In +particular, by the time of Ptolemy (_ca._ A.D. 120) it had led to the +successive inventions of the anaphoric clock and of the planispheric +astrolabe.[12] Both these devices consist of a pair of stereographic +projections, one of the celestial sphere with its stars and ecliptic and +tropics, the other of the lines of altitude and azimuth as set for an +observer in a place at some particular latitude. + +In the astrolabe, an openwork metal rete containing markings for the +stars, etc., may be rotated by hand over a disc on which the lines of +altitude and azimuth are inscribed. In the anaphoric clock a disc +engraved with the stars is rotated automatically behind a fixed grille +of wires marking lines of altitude and azimuth. Power for rotating the +disc is provided by a float rising in a clepsydra jar and connected, by +a rope or chain passing over a pulley to a counterweight or by a rack +and pinion, to an axle which supported the rotating disc and +communicated this motion to it.[13] + +[Illustration: Figure 5. PLATE OF SALZBURG ANAPHORIC CLOCK, a +reconstruction (see footnote 14) based on a photograph of the remaining +fragment. (_Courtesy of Oxford University Press._)] + +Parts of two such discs from anaphoric clocks have been found, one at +Salzburg[14] and one at Grand in the Vosges,[15] both of them dating +from the 2nd century A.D. Fortunately there is sufficient evidence to +reconstruct the Salzburg disc and show that it must have been originally +about 170 cm. in diameter, a heavy sheet of bronze to be turned by the +small power provided by a float, and a large and impressive device when +working (see fig. 5). Literary accounts of the anaphoric clock have been +analyzed by Drachmann; there is no evidence of the representation of +planets moved either by hand or by automatic gearing, only in the +important case of the sun was such a feature included of necessity. A +model "sun" on a pin could be plugged in to any one of 360 holes drilled +in at equal intervals along the band of the ecliptic. This pin could be +moved each day so that the anaphoric clock kept step with the seasonal +variation of the times of sunrise and sunset and the lengths of day and +night. + +The anaphoric clock is not only the origin of the astrolabe and of all +later planetary models, it is also the first clock dial, setting a +standard for "clockwise" rotation, and leaving its mark in the rotating +dial and stationary pointer found on the earliest time-keeping clocks +before the change was made to a fixed dial and moving hand. + +We come finally to a piece of archaeological evidence that surpasses all +else. Though badly preserved and little studied it might well be the +most important classical object ever found; entailing a complete +re-estimation of the technical prowess of the Hellenistic Greeks. In +1901 a sunken treasure ship was discovered lying off the island of +Antikythera, between Greece and Crete.[16] Many beautiful classical +works of statuary were recovered from it, and these are now amongst the +greatest treasures of the National Museum at Athens, Greece. Besides +these obviously desirable art relics, there came to the surface some +curious pieces of metal, accompanied by traces of what may have been a +wooden casing. Two thousand years under the sea had reduced the metal to +a mess of corroded fragments of plates, powdered verdigris, and still +recognizable pieces of gear wheels. + +If it were not for the established dates for other treasure from this +ship, especially the minor objects found, and for traces of inscriptions +on this metal device written in letters agreeing epigraphically with the +other objects, one would have little doubt in supposing that such a +complicated piece of machinery dated from the 18th century, at the +earliest. As it is, estimates agree on _ca._ 65 B.C. ±10 years, and we +can be sure that the machine is of Hellenistic origin, possibly from +Rhodes or Cos. + +[Illustration: Figure 6.--ANTIKYTHERA MACHINE, LARGEST FRAGMENT. (_Photo +courtesy of National Museum, Athens._)] + +The inscriptions, only partly legible, lead one to believe that we are +dealing with an astronomical calculating mechanism of some sort. This is +born out by the mechanical construction evident on the fragments. The +largest one (fig. 6) contains a multiplicity of gearing involving an +annular gear working epicyclic gearing on a turntable, a crown wheel, +and at least four separate trains of smaller gears, as well as a +4-spoked driving wheel. One of the smaller fragments (fig. 7, bottom) +contains a series of movable rings which may have served to carry +movable scales on one of the three dials. The third fragment (fig. 7, +top) has a pair of rings carefully engraved and graduated in degrees of +the zodiac (this is, incidentally, the oldest engraved scale known, and +micrometric measurements on photographs have indicated a maximum +inaccuracy of about 1/2° in the 45° present). + +[Illustration: Figure 7.--ANTIKYTHERA MACHINE, TWO SMALLER FRAGMENTS. +(_Photo courtesy of National Museum, Athens._)] + +Unfortunately, the very difficult task of cleaning the fragments is +slow, and no publication has yet given sufficient detail for an adequate +explanation of this object. One can only say that although the problems +of restoration and mechanical analysis are peculiarly great, this must +stand as the most important scientific artifact preserved from +antiquity. + +Some technical details can be gleaned however. The shape of the gear +teeth appears to be almost exactly equilateral triangles in all cases +(fig. 8), and square shanks may be seen at the centers of some of the +wheels. No wheel is quite complete enough for a count of gear teeth, but +a provisional reconstruction by Theophanidis (fig. 9) has shown that the +appearances are consistent with the theory that the purpose of the +gears was to provide the correct angular ratios to move the sun and +planets at their appropriate relative speeds. + +[Illustration: Figure 8.--ANTIKYTHERA MACHINE, DETAIL FROM FIGURE 6, +showing gearing. (_Photo courtesy of National Museum, Athens._)] + +Thus, if the evidence of the Antikythera machine is to be taken at its +face value, we have, already in classical times, the use of astronomical +devices as complicated as any clock. In any case, the material supplied +by the works ascribed to Archimedes, Hero, and Vitruvius, and the more +certain evidence of the anaphoric clocks is sufficient to show that +there was a strong classical tradition of such machines, a tradition +that inspired, even if it did not directly influence, later developments +in Islam and Europe on the one side, and, just possibly, China on the +other. + + _Note added in proof_: + + Since the above lines were written, I have been privileged + to make a full examination of the fragments in the + National Museum in Athens. As a result we can read much + more inscription and make out many more details of the + mechanism. The cleaning and disentangling of the fragments + by the museum staff has proceeded to the stage where one + can assert much more positively that the device was an + astronomical computer for sidereal, solar, lunar, and + possibly also planetary phenomena. (See my article in the + _Scientific American_, June 1959, vol. 200, No. 6, pp. + 60-67.) Relevant to the present study, it must also be + noted at this point that the machine is now shown to be + strongly related to the geared astrolabe of al-Biruni and + thereby the Hellenistic, Islamic, and European + developments are drawn together even more tightly. + +Let us now turn our attention to those civilizations which were +intermediaries, geographically and culturally, between Greece and +medieval Europe, and between both of these and China. From India there +are only two references, very closely related and appearing in the best +known astronomical texts in connection with descriptions of the +armillary sphere and celestial globe. These texts are both quite +garbled, but so far as one may understand them, it seems that the types +of spheres and globes mentioned are more akin to those current in China +than in the West. The relevant portions of text are as follows (italics +supplied): + + The circle of the horizon is midway of the sphere. As + covered with a casing and as left uncovered, it is the + sphere surrounded by Lokāloka [the mountain range which + formed the boundary of the universe in puranic geography]. + By the application of water is made ascertainment of the + revolution of time. One may construct a sphere-instrument + combined with quicksilver: this is a mystery; if plainly + described, it would be generally intelligible in the + world. Therefore let the supreme sphere be constructed + according to the instruction of the preceptor [guru]. In + each successive age this construction, having become lost, + is, by the Sun's favour, again revealed to some one or + other, at his pleasure. So also, one should construct + instruments in order to ascertain time. When quite alone, + one should apply quicksilver to the wonder-causing + instrument. By the gnomon, staff, arc, wheel, instruments + for taking the shadow of various kinds.... By + water-instruments, the vessel, by the peacock, man, + monkey, and by stringed sand-receptacles one may determine + time accurately. Quicksilver-holes, water, and cords, and + oil and water, mercury and sand are used in these: these + applications, too, are difficult. + + Sūrya Siddhānta_, xiii, 15-22, + E. Burgess' translation, New Haven, 1860. + +[Illustration: Figure 9.--ANTIKYTHERA MACHINE, PARTIAL RECONSTRUCTION +BY THEOPHANIDIS (see footnote 16).] + + A self-revolving instrument [or swayanvaha yantra]: Make a + wheel of light wood and in its circumference put hollow + spokes all having bores of the same diameter, and let them + be placed at equal distances from each other; and let + them also be placed at an angle verging somewhat from the + perpendicular: then half fill these hollow spokes with + mercury; the wheel thus filled will, when placed on an + axis supported by two posts, revolve of itself. + + Or scoop out a canal in the tire of the wheel and then + plastering leaves of the Tȧla tree over this canal with + wax, fill one half of this canal with water and the other + half with mercury, till the water begins to come out, and + then cork up the orifice left open for filling the wheel. + The wheel will then revolve of itself, drawn around by the + water. + + Description of a syphon: Make up a tube of copper or other + metal, and bend it in the form of an Ankus'a or elephant + hook, fill it with water and stop up both ends. And then + putting one end into a reservoir of water let the other + end remain suspended outside. Now uncork both ends. The + water of the reservoir will be wholly sucked up and fall + outside. + + Now attach to the rim of the before described + self-revolving wheel a number of water-pots, and place the + wheel and these pots like the water wheel so that the + water from the lower end of the tube flowing into them on + one side shall set the wheel in motion, impelled by the + additional weight of the pots thus filled. The water + discharge from the pots as they reach the bottom of the + revolving wheel, should be drawn off into the reservoir + before alluded to by means of a water-course or pipe. + + The self-revolving machine [mentioned by _Lalla_, etc.] + which has a tube with its lower end open is a vulgar + machine on account of its being dependant, because that + which manifests an ingenious and not a rustic contrivance + is said to be a machine. + + And moreover many self-revolving machines are to be met + with, but their motion is procured by a trick. They are + not connected with the subject under discussion. I have + been induced to mention the construction of these, merely + because they have been mentioned by former astronomers. + + _Siddhānta Siromaṇi_, xi, 50-57, L. Wilkinson's + translation, revised by Bȧpu̇ deva S(h)ȧstri, + Calcutta, 1861. + +Before proceeding to an investigation of the content of these texts it +is of considerable importance to establish dates for them, though there +are many difficulties in establishing any chronology for Hindu +astronomy. The _Sūrya Siddhānta_ is known to date, in its original +form, from the early Middle Ages, _ca._ 500. The section in question is +however quite evidently an interpolation from a later recension, most +probably that which established the complete text as it now stands; it +has been variously dated as _ca._ 1000 to _ca._ 1150 A.D. The date of +the _Siddhānta Siromaṇi_ is more certain for we know it was +written in about 1150 by Bhāskara (born 1114). Thus both these +passages must have been written within a century of the great clock-tower +made by Su Sung. The technical details will lead us to suppose there is +more than a temporal connection. + +We have already noted that the armillary spheres and celestial globes +described just before these extracts are more similar in design to +Chinese than to Ptolemaic practice. The mention of mercury and of sand +as alternatives to water for the clock's fluid is another feature very +prevalent in Chinese but absent in the Greek texts. Both texts seem +conscious of the complexity of these devices and there is a hint (it is +lost and revealed) that the story has been transmitted, only half +understood, from another age or culture. It should also be noted that +the mentions of cords and strings rather than gears, and the use of +spheres rather than planispheres would suggest we are dealing with +devices similar to the earliest Greek models rather than the later +devices, or with the Chinese practice. + +A quite new and important note is injected by the passage from the +Bhāskara text. Obviously intrusive in this astronomical text we have +the description of two "perpetual motion wheels" together with a third, +castigated by the author, which helps its perpetuity by letting water +flow from a reservoir by means of a syphon and drop into pots around the +circumference of the wheel. These seem to be the basis also, in the +extract from the _Sūrya Siddhānta_, of the "wonder-causing +instrument" to which mercury must be applied. + +In the next sections we shall show that this idea of a perpetual motion +device occurs again in conjunction with astronomical models in Islam and +shortly afterwards in medieval Europe. At each occurrence, as here, +there are echoes of other cultures. In addition to those already +mentioned we find the otherwise mysterious "peacock, man and monkey," +cited as parts of the jackwork of astronomical clocks of Islam, +associated with the weight drive so essential to the later horology in +Europe. + +We have already seen that in classical times there were already two +different types of protoclocks; one, which may be termed +"nonmathematical," designed only to give a visual aid in the conception +of the cosmos, the other, which may be termed "mathematical" in which +stereographic projection or gearing was employed to make the device a +quantitative rather than qualitative representation. These two lines +occur again in the Islamic culture area. + +Nonmathematical protoclocks which are scarcely removed from the +classical forms appear continuously through the Byzantine era and in +Islam as soon as it recovered from the first shocks of its formation. +Procopius (died _ca._ 535) describes a monumental water clock which was +erected in Gaza _ca._ 500.[17] It contained impressive jackwork, such as +a Medusa head which rolled its eyes every hour on the hour, exhibiting +the time through lighted apertures and showing mythological +interpretations of the cosmos. All these effects were produced by +Heronic techniques, using hydraulic power and puppets moved by strings, +rather than with gearing. + +Again in 807 a similarly marvelous exhibition clock made of bronze was +sent by Harun-al-Rashid to the Emperor Charlemagne; it seems to have +been of the same type, with automata and hydraulic works. For the +succeeding few centuries, Islam was in its Golden Age of development of +technical astronomy (_ca._ 950-1150) and attention may have been +concentrated on the more mathematical protoclocks. Towards the end of +the 12th century, however, there was a revival of the old tradition, +mainly at the court of the Emperor Saladin (1146-1173) when a great +automaton water clock, more magnificent than any hitherto, was erected +in Damascus. It was rebuilt, after 1168, by Muḥammad b. 'Alī b. +Rustum, and repaired and improved by his son, Fakhr ad-dīn +Riḍwān b. Muḥammad,[18] who is most important as the author of +a book which describes in considerable technical detail the construction +of this and other protoclocks. Closely associated with his book one also +finds texts dealing with perpetual-motion devices, which we shall +consider later. + +During the century following this horological exuberance in Damascus, +the center of gravity of Islamic astronomy shifted from the East to the +Hispano-Moorish West. At the same time there comes more evidence that +the line of mathematical protoclocks had not been left unattended. This +is suggested by a description given by Trithemius of another royal gift +from East to West which seems to have been different from the automata +and hydraulic devices of the tradition from Procopius to +Riḍwān:[19] + + In the same year [1232] the Saladin of Egypt sent by his + ambassadors as a gift to the emperor Frederic a valuable + machine of wonderful construction worth more than five + thousand ducats. For it appeared to resemble internally a + celestial globe in which figures of the sun, moon, and + other planets formed with the greatest skill moved, being + impelled by weights and wheels, so that performing their + course in certain and fixed intervals they pointed out the + hour night and day with infallible certainty; also the + twelve signs of the zodiac with certain appropriate + characters, moved with the firmament, contained within + themselves the course of the planets. + +[Illustration: Figure 10.--CALENDRICAL GEARING DESIGNED BY AL-BIRUNI, +_ca._ A.D. 1000. The gear train count is 40-10+7-59+19-59+24-48. The +gear of 48 therefore makes 19 (annual) rotations while that of 19-59 +shows 118 double lunations of 29+30=59 days. The gear of 40 shows a +(lunar) rotation in exactly 28 days, and the center pinions 7+10 rotate +in exactly one week. After Wiedemann (see footnote 20).] + +The phrase "resembled internally" is of especial interest in this +passage; it may perhaps arise as a mistranslation of the technical term +for stereographic projection of the sphere, and if so the device might +have been an anaphoric clock or some other astrolabic device. + +This is made more probable by the existence of a specifically Islamic +concentration on the astrolabe, and on its planetary companion +instrument, the equatorium, as devices for mechanizing computation by +use of geometrical analogues. The ordinary planispheric astrolabe, of +course, was known in Islam from its first days until almost the present +time. From the time of al-Biruni (_ca._ 1000)--significantly, perhaps, +he is well known for his travel account of India--there is remarkable +innovation. + +Most cogent to our purpose is a text, described for the first time by +Wiedemann,[20] in which al-Biruni explains how a special train of +gearing may be used to show the revolutions of the sun and moon at their +relative rates and to demonstrate the changing phase of the moon, +features of fundamental importance in the Islamic (lunar) calendrical +system. This device necessarily uses gear wheels with an odd number of +teeth (_e.g._, 7, 19, 59) as dictated by the astronomical constants +involved (see fig. 10). The teeth are shaped like equilateral triangles +and square shanks are used, exactly as with the Antikythera machine. +Horse-headed wedges are used for fixing; a tradition borrowed from the +horse-shaped _Farās_ used to fasten the traditional astrolabe. Of +special interest for us is the lunar phase diagram, which is just the +same in form and structure as the lunar volvelle that occurs later in +horology and is still so commonly found today, especially as a +decoration for the dial of grandfather clocks. + +[Illustration: Figure 11.--GEARED ASTROLABE BY MUḤAMMAD B. ABĪ BAKR +OF ISFAHAN, A.D. 1221-1222. (_Photo courtesy of Science Museum, +London._)] + +Biruni's calendrical machine is the earliest complicated geared device +on record and it is therefore all the more significant that it carries a +feature found in later clocks. From the manuscript description alone one +could not tell whether it was designed for automatic action or merely to +be turned by hand. Fortunately this point is made clear by the most +happy survival of an intact specimen of this very device, without doubt +the oldest geared machine in existence in a complete state. + +[Illustration: Figure 12.--GEARING FROM ASTROLABE SHOWN IN FIGURE 11. +The gear train count is as follows: 48-13+8-64+64-64+10-60. The pinion +of 8 has been incorrectly replaced by a more modern pinion of 10. The +gear of 48 should make 13 (lunar) rotations while the double gear of +64+64 makes 6 revolutions of double months (of 29-30 days) and the gear +of 60 makes a single turn in the hegiral year of 354 days. (_Photo +courtesy of Science Museum, London._)] + +This landmark in the history of science and technology is now preserved +at the Museum of the History of Science, Oxford, England.[21] It is an +astrolabe, dated 1221-22 and signed by the maker, Muḥammad b. Abī +Bakr (died 1231-32) of Isfahan, Persia (see figs. 11 and 12). The very +close resemblance to the design of Biruni is quite apparent, though the +gearing has been simplified very cleverly so that only one wheel has an +odd number of teeth (13), the rest being much easier to mark out +geometrically (_e.g._, 10, 48, 60, and 64 teeth). The lunar phase +volvelle can be seen through the circular opening at the back of the +astrolabe. It is quite certain that no automatic action is intended; +when the central pivot is turned, by hand, probably by using the +astrolabe rete as a "handle," the calendrical circles and the lunar +phase are moved accordingly. Using one turn for a day would be too slow +for useful re-setting of the instrument, in practice a turn corresponds +more nearly to an interval of one week. + +[Illustration: Figure 13.--ASTROLABE CLOCK, REGULATED BY A MERCURY DRUM, +from the Alfonsine _Libros del saber_ (see footnote 22).] + +In addition to this geared development of the astrolabe, the same period +in Islam brought forth a new device, the equatorium, a mechanical model +designed to simulate the geometrical constructions used for finding the +positions of the planets in Ptolemaic astronomy. The method may have +originated already in classical times, a simple device being described +by Proclus Diadochus (_ca._ 450), but the first general, though crude, +planetary equatorium seems to have been described by Abulcacim Abnacahm +(_ca._ 1025) in Granada; it has been handed down to us in the archaic +Castilian of the Alfonsine _Libros del saber_.[22] The sections of this +book, dealing with the _Laminas de las VII Planetas_, describe not only +this instrument but also the improved modification introduced by +Azarchiel (born _ca._ 1029, died _ca._ 1087). + +No Islamic examples of the equatorium have survived, but from this +period onward, there appears to have been a long and active tradition of +them, and ultimately they were transmitted to the West, along with the +rest of the Alfonsine corpus. More important for our argument is that +they were the basis for the mechanized astronomical models of Richard of +Wallingford (_ca._ 1320) and probably others, and for the already +mentioned great astronomical clock of de Dondi. In fact, the complicated +gearwork and dials of de Dondi's clock constitute a series of equatoria, +mechanized in just the same way as the calendrical device described by +Biruni. + +It is evident that we are coming nearer now to the beginning of the true +mechanical clock, and our last step, also from the Alfonsine corpus of +western Islam, provides us with an important link between the anaphoric +clock, the weight drive, and a most curious perpetual-motion device, the +mercury wheel, used as an escapement or regulator. The Alfonsine book on +clocks contains descriptions of five devices in all, four of them being +due to Isaac b. Sid (two sundials, an automaton water-clock and the +present mercury clock) and one to Samuel ha-Levi Adulafia (a candle +clock)--they were probably composed just before _ca._ 1276-77. + +[Illustration: Figure 14.--ISLAMIC PERPETUAL MOTION WHEEL, after +manuscript cited by Schmeller (see footnote 26).] + +The mercury clock of Isaac b. Sid consists of an astrolabe dial, rotated +as in the anaphoric clock, and fitted with 30 leaf-shaped gear teeth +(see fig. 13). These are driven by a pinion of 6 leaves mounted on a +horizontal axle (shown very diagrammatically in the illustration) and at +the other end of this axle is a wheel on which is mounted the special +mercury drum which is powered by a normal weight drive. + +It is the mercury drum which forms the most novel feature of this +device; the fluid, constrained in 12 chambers so as to just fill 6 of +them, must slowly filter through small holes in the constraining walls. +In practice, of course, the top mercury surfaces will not be level, but +higher on the right so as to balance dynamically the moment of the +applied weight on its driven rope. This curious arrangement shows point +of resemblance to the Indian "mercury-holes," to the perpetual-motion +devices found in the medieval European tradition and also in the texts +associated with Riḍwān, which we shall next examine. + +[Illustration: Figure 15.--ANOTHER PERPETUAL MOTION WHEEL, after the +text cited in figure 14.] + +It is of the greatest interest to our theme that the Islamic +contributions to horology and perpetual motion seem to form a closely +knit corpus. A most important series of horological texts, including +those of Riḍwān and al-Jazarī, have been edited by Wiedemann +and Hauser.[23] Other Islamic texts give versions of the water clocks +and automata of Archimedes and of Hero and Philo of Alexandria.[24] In +at least three cases[25] these texts are found also associated with +texts describing perpetual-motion wheels and other hydraulic devices. +Three manuscripts of this type have been published in German translation +by Schmeller.[26] The devices include a many chambered wheel (see fig. +14) similar to the Alfonsine mercury "escapement," a wheel of slanting +tubes constructed like the noria (see fig. 15), wheels of weights +swinging on arms as described by Villard of Honnecourt, and a remarkable +device which seems to be the earliest known example of a weight drive. +This latter machine is a pump, in which a chain of buckets is used to +raise water by passing over a pulley which is geared to a drum powered +by a falling weight (see fig. 16); perhaps for balance, the whole +arrangement is made in duplicate with common axles for the corresponding +parts. + +[Illustration: Figure 16.--ISLAMIC PUMP POWERED BY A WEIGHT DRIVE, +after the text cited in figure 14.] + +The Islamic tradition of water clocks did not involve the use of gears, +though very occasionally a pair is used to turn power through an angle +when this is dictated by the use of a water wheel in the automata. In +the main, everything is worked by floats and strings or by hydraulic or +pneumatic forces, as in Heros devices. The automata are very elaborate, +with figures of men, monkeys, peacocks, etc., symbolizing the passage of +hours. + + +MEDIEVAL EUROPE + +Echoes from nearly all the developments already noted from other parts +of the world are found to occur in medieval Europe, often coming +through channels of communication more precisely determinable than +those hitherto mentioned. Before the influx of Islamic learning at the +time of transmission of the Toledo Tables (12th century) and the +Alfonsine Tables (which reached Paris _ca._ 1292), there are occasional +references to the most primitive mechanized "visual aids" in astronomy. + +The most famous of these occurs in an historical account by Richer of +Rheims about his teacher Gerbert (born 946, later Pope Sylvester II, +990-1003). Several instruments made by Gerbert are described in detail; +he includes a fine celestial globe made of wood covered with horsehide +and having the stars and lines painted in color, and an armillary sphere +having sighting tubes similar to those always found on Chinese +instruments but never on the Ptolemaic variety. Lastly, he cites "the +construction of a sphere, most suitable for recognizing the planets," +but unfortunately it is not clear from the description whether or not +the model planets were actually to be animated mechanically. The text +runs:[27] + + Within this oblique circle (the zodiac on the ecliptic of + the globe) he hung the circles of the wandering stars (the + planets) with marvellous ingenuity, whose orbits, heights + and even the distance from each other he demonstrated to + his pupils most effectually. Just how he accomplished this + it is unsuitable to enter into here because of its extent + lest we should appear to be wandering from our main theme. + +Thus, although there is a hint of mechanical complexity, there is really +no justification for such an assumption; the description might well +imply only a zodiac band on which the orbits of the planets were +painted. On the other hand it is not inconceivable that Gerbert could +have learned something of Islamic and other extra-European traditions +during his period of study with the Bishop of Barcelona--a traveling +scholarship that seems to have had many repercussions on the whole field +of European scholarship. + +Once the floodgates of Arabic learning were opened, a stream of +mechanized astronomical models poured into Europe. Astrolabes and +equatoria rapidly became very popular, mainly through the reason for +which they had been first devised, the avoidance of tedious written +computation. Many medieval astrolabes have survived, and at least three +medieval equatoria are known. Chaucer is well known for his treatise on +the astrolabe; a manuscript in Cambridge, containing a companion +treatise on the equatorium, has been tentatively suggested by the +present author as also being the work of Chaucer and the only piece +written in his own hand. + +The geared astrolabe of al-Biruni is another type of protoclock to have +been transmitted. A specimen in the Science Museum, London,[28] though +unfortunately now incomplete, has a very sophistocated arrangement of +gears for moving pointers to indicate the correct relative positions and +movements of the sun and moon (see figs. 17 and 18). Like the earlier +Muslim example it contains wheels with odd numbers of gear teeth (14, +27, 39); however, the teeth are no longer equilateral in shape, but +approximate a more modern slightly rounded form. This example is French +and appears to date from _ca._ 1300. Another Gothic astrolabe with a +similar gear ring on the rete, said to date from _ca._ 1400 (it could +well be much earlier) is now in the Billmeier collection (London).[29] + +Turning from the mechanized astrolabe to the mechanized equatorium, we +find the work of Richard of Wallingford (1292?-1336) of the greatest +interest as providing an immediate precursor to that of de Dondi. He +was the son of an ingenious blacksmith, making his way to Merton +College, Oxford, then the most active and original school of astronomy +in Europe, and winning later distinction as Abbot of St. Albans. A text +by him, dated 1326-27, described in detail the construction of a great +equatorium, more exact and much more elaborate than any that had gone +before.[30] Nevertheless it is evidently a normal manually operated +device like all the others. In addition to this instrument, Richard is +said to have constructed _ca._ 1320, a fine planetary clock for his +Abbey.[31] Bale, who seems to have seen it, regarded it as without rival +in Europe, and the greatest curiosity of his time. Unfortunately, the +issue was confused by Leland, who identified it as the Albion (_i.e._, +all-by one), the name Richard gives to his manual equatorium. This clock +was indeed so complex that Edward III censured the Abbot for spending so +much money on it, but Richard replied that after his death nobody would +be able to make such a thing again. He is said to have left a text +describing the construction of this clock, but the absence of such a +work has led many modern writers to support Leland's identification and +suppose that the device was not a mechanical clock. + +[Illustration: Figure 17.--FRENCH GEARED ASTROLABE OF TREFOIL GOTHIC +DESIGN, _ca._ A.D. 1300. The gearing on the pointer is, from the +center: (32)/14-45+27-39, the last meshing with a concave annular gear +of 180 teeth around the rim of the rete of the astrolabe. A second +pointer, geared to this so as to follow the Moon, seems to be lacking. +(_Photo courtesy of Science Museum. London._)] + +[Illustration: Figure 18.--GEAR TRAIN OF POINTER in figure 17. (_Photo +courtesy of Science Museum, London._)] + +A corrective for this view is to be had from a St. Albans manuscript +(now at Gonville and Caius College, Cambridge) that described the +methods for setting out toothed wheels for an astronomical horologium +designed to show the motions of the planets. Although the manuscript +copy is to be dated _ca._ 1340, it clearly indicates that a geared +planetary device was known in St. Albans at an early date, and it is +reasonable to suppose that this was in fact the machine made by Richard +of Wallingford. Unfortunately the text does not appear to give any +relevant information about the presence of an escapement or any other +regulatory device, nor does it mention the source of power.[32] Now a +geared version of the Albion would appear to correspond very closely +indeed to the dial-work which forms the greater part of the de Dondi +clock, and for this reason we suggest now that the two clocks were very +closely related in other ways too. This, circumstantial though it be, is +evidence for thinking that the weight drive and some form of escapement +were known to Richard of Wallingford, _ca._ 1320. It would narrow the +gap between the clock and the protoclocks to less than half a century, +perhaps a single generation, in the interval _ca._ 1285-1320. In this +connection it may be of interest that Richard of Wallingford knew only +the Toledo tables corpus, that of the Alfonsine school did not arrive in +England until after his death. + +There are, of course, many literary references to the water-clocks in +medieval literature. In fact most of these are from quotations which +have often been produced erroneously in the history of the mechanical +clock, thereby providing many misleading starts for that history, as +noted previously in the discussion of the horologium. There are however +enough mentions to make it certain that water clocks of some sort were +in use, especially for ecclesiastic purposes, from the end of the 12th +century onwards. Thus, Jocelin of Brakelond tells of a fire in the Abbey +Church of Bury St. Edmunds in the year 1198.[33] The relics would have +been destroyed during the night, but just at the crucial moment the +clock bell sounded for matins and the master of the vestry sounded the +alarm. On this "the young men amongst us ran to get water, some to the +well and others to the clock"--probably the sole occasion on which a +clock served as a fire hydrant. + +It seems probable that some of these water clocks could have been simple +drip clepsydras, with perhaps a striking arrangement added. A most +fortunate discovery by Drover has now brought to light a manuscript +illumination that shows that these water clocks, at least by _ca,_ 1285, +had become more complex and were rather similar in appearance to the +Alfonsine mercury drum.[34] The illustration (fig. 19) is from a +moralized Bible written in northern France, and accompanies the passage +where King Hezekiah is given a sign by the Lord, the sun being moved +back ten steps of the clock. The picture clearly shows the central water +wheel and below it a dog's head spout gushing water into a bucket +supported by chains, with a (weight?) cord running behind. Above the +wheel is a carillon of bells, and to one side a rosette which might be a +fly or a model sun. The wheel appears to have 15 compartments, each with +a central hole (perhaps similar to that in the Alfonsine clock) and it +is supported on a square axle by a bracket, the axle being wedged in the +traditional fashion. The projections at the edge of the wheel might be +gear teeth, but more likely they are used only for tripping the striking +mechanism. If it were not for the running water spout it would be very +close to the Alfonsine model; but with this evidence it seems impossible +to arrive at a clear mechanical interpretation. + +From the adjacent region there is another account of a striking water +clock, the evidence being inscriptions on slates, discovered in Villers +Abbey near Brussels;[35] these may be closely dated as 1267 or 1268 and +provide the remains of a memorandum for the sacrist and his assistants +in charge of the clock. + + Always set the clock, however long you may delay on [the + letter "A"] afterwards you shall pour water from the + little pot (pottulo) that is there, into the reservoir + (cacabum) until it reaches the prescribed level, and you + must do the same when you set [the clock] after compline + so that you may sleep soundly. + +A quite different sort of evidence is to be had from the writings of +Robertus Anglicus in 1271 where one gets the impression that just at +this time there was active interest in the attempt to make a +weight-driven anaphoric clock and to regulate its motion by some +unstated method so that it would keep time with the diurnal rotation of +the heavens:[36] + + Nor it is possible for any clock to follow the judgment of + astronomy with complete accuracy. Yet clockmakers + (artifices horologiorum) are trying to make a wheel + (circulum) which will make one complete revolution for + every one of the equinoctial circle, but they cannot quite + perfect their work. But if they could, it would be a + really accurate clock (horologium verax valde) and worth + more than an astrolabe or other astronomical instrument + for reckoning the hours, if one knew how to do this + according to the method aforesaid. The method of making + such a clock would be this, that a man make a disc + (circulum) of uniform weight in every part so far as could + possibly be done. Then a lead weight should be hung from + the axis of that wheel (axi ipsius rote) and this weight + would move that wheel so that it would complete one + revolution from sunrise to sunrise, minus as much time as + about one degree rises according to an approximately + correct estimate. For from sunrise to sunrise, the whole + equinoctial rises, and about one degree more, through + which degree the sun moves against the motion of the + firmament in the course of a natural day. Moreover, this + could be done more accurately if an astrolabe were + constructed with a network on which the entire equinoctial + circle was divided up. + +[Illustration: Figure 19.--MANUSCRIPT ILLUMINATION OF A MEDIEVAL +WATERCLOCK, showing a partitioned wheel, a weight drive, and a carillion +for striking. From Drover (see footnote 34).] + +The text then continues with technical astronomical details of the +slight difference between the rate of rotation of the sun and of the +fixed stars (because of the annual rotation of the sun amongst the +stars) but it gives no indication of any regulatory device. Again it +should be noted, this source comes from France; Robertus, though of +English origin, apparently being then a lecturer either at the +University of Paris or at that of Montpellier. The date of this passage, +1271, has been taken as a _terminus post quem_ for the invention of the +mechanical clock. In the next section we shall describe the text of +Peter Peregrinus, very close to this in place and date, which describes +just such a machine, conflating it with accounts of an armillary sphere, +perpetual motion, and the magnetic compass--so bringing all these +threads together for the first time in Europe. + +[Illustration: Figure 20.--ARRANGEMENT FOR TURNING A FIGURE OF AN ANGEL. +It has been alleged that this drawing by Villard represents an +escapement. After Lassus (see footnote 37).] + +We have reserved to the last one section of evidence which may or may +not be misleading, the famous notebook of Villard (Wilars) of +Honnecourt, near Cambrai. The album, attributed to the period 1240-1251, +contains many drawings with short annotations, three of which are of +special interest to our investigations.[37] These comprise a steeplelike +structure labeled "cest li masons don orologe" (this is the house of a +clock), a device including a rope, wheel and axle (fig. 20), marked "par +chu fait om un angle tenir son doit ades vers le solel" (by this means +an angel is made to keep his finger directed towards the sun), and a +perpetual motion wheel which we shall reserve for later discussion. + +The clock tower, according to Drover, shows no place for a dial but +suggests the use of bells because of its open structure, suitable for +letting out the sound. Moreover, he suggests that the delicacy of the +line indicates that it was not really a full-size steeple but rather a +small towerlike structure standing only a few feet high within the +church. There is, alas, nothing to tell us about the clock it was +intended to house; most probably it was a water clock similar to that of +the illustrated Bible of _ca._ 1285. + +The drawing of the rope, wheel and axles, for turning an angel to point +towards the sun can have a simple explanation or a more complicated one. +If taken at its face value the wheel on its horizontal axis acts as a +windlass connected by the counterpoised rope to the vertical shaft which +it turns, thereby moving (by hand) the figure of an angel (not shown) +fixed to the top of this latter shaft. Such an explanation was in fact +suggested by M. Quicherat,[38] who first called attention to the Villard +album and pointed out that a leaden angel existed in Chartres before the +fire there in 1836. It is a view also supported from another drawing in +the album which describes an eagle whose head is made to turn towards +the deacon when he reads the Gospel. Slight pressure on the tail of the +bird causes a similar rope mechanism to operate. + +A quite different interpretation has been suggested by Frémont;[39] he +believes that the wheel may have acted as a fly-wheel and the ropes and +counterpoises, turning first one way then the other acted as a sort of +mechanical escapement. Such an arrangement is however mechanically +impossible without some complicated free-wheeling device between the +drive and the escapement, and its only effect would be to oscillate the +angel rapidly rather than turn it steadily. I believe that Frémont, +over-anxious to provide a protoescapement, has done too much violence to +the facts and turned away without good reason from the more simple and +reasonable explanation. It is nevertheless still possible to adopt this +simple interpretation and yet to have the system as part of a clock. If +the left-hand counterpoise, conveniently raised higher than that on the +right, is considered as a float fitting into a clepsydra jar, instead of +as a simple weight, one would have a very suitable automatic system for +turning the angel. On this explanation, the purpose of the wheel would +be merely to provide the manual adjustment necessary to set the angel +from time to time, compensating for irremediable inaccuracies of the +clepsydra. + +[Illustration: Figure 21.--VILLARD'S PERPETUAL MOTION WHEEL, from Lassus +(see footnote 37).] + +Having discussed the Villard drawings which are already cited in +horological literature, we must draw attention to the fact that this +medieval architect also gives an illustration of a perpetual motion +wheel. In this case (fig. 21) it is of the type having weights at the +end of swinging arms, a type that occurs very frequently at later dates +in Europe and is also given in the Islamic texts. We cannot, in this +case, suggest that drawings of clocks and of perpetual motion devices +occur together by more than a coincidence, for Villard seems to have +been interested in most sorts of mechanical device. But even this type +of coincidence becomes somewhat striking when repeated often enough. It +seems that each early mention of "self-moving wheels" occurs in +connection with some sort of clock or mechanized astronomical device. + +Having now completed a survey of the traditions of astronomical models, +we have seen that many types of device embodying features later found in +mechanical clocks evolved through various cultures and flowed into +Europe, coming together in a burst of multifarious activity during the +second half of the 13th century, notably in the region of France. We +must now attempt to fill the residual gap, and in so doing examine the +importance of perpetual motion devices, mechanical and magnetic, in the +crucial transition from protoclock to mechanical-escapement clock. + + + + +Perpetual Motion and the Clock before de Dondi + +We have already noted, more or less briefly, several instances of the +use of wheels "moving by themselves" or the use of a fluid for purposes +other than as a motive power. Chronologically arranged, these are the +Indian devices of _ca._ 1150 or a little earlier, as those of Riḍwān +_ca._ 1200, that of the Alfonsine mercury clock, _ca._ 1272, and the +French Bible illumination of _ca._ 1285. This strongly suggests a steady +transmission from East to West, and on the basis of it, we now +tentatively propose an additional step, a transmission from China to +India and perhaps further West, _ca._ 1100, and possibly reinforced by +further transmissions at later dates. + +One need only assume the existence of vague traveler's tales about the +existence of the 11th-century Chinese clocks with their astronomical +models and jackwork and with their great wheel, apparently moving by +itself but using water having no external inlet or outlet. Such a +stimulus, acting as it did on a later occasion when Galileo received +word of the invention of the telescope in the Low Countries, might +easily lead to the re-invention of just such perpetual-motion wheels as +we have already noted. In many ways, once the idea has been suggested it +is natural to associate such a perpetual motion with the incessant +diurnal rotation of the heavens. Without some such stimulus however it +is difficult to explain why this association did not occur earlier, and +why, once it comes there seems to be such a chronological procession +from culture to culture. + +We now turn to what is undoubtedly the most curious part of this story, +in which automatically moving astronomical models and perpetual motion +wheels are linked with the earliest texts on magnetism and the magnetic +compass, another subject with a singularly troubled historical origin. +The key text in this is the famous _Epistle on the magnet_, written by +Peter Peregrinus, a Picard, in an army camp at the Siege of Lucera and +dated August 8, 1269.[40] In spite of the precise dating it is certain +that the work was done long before, for it is quoted unmistakably by +Roger Bacon in at least three places, one of which must have been +written before _ca._ 1250.[41] + +The _Epistle_ contains two parts; in the first there is a general +account of magnetism and the properties of the loadstone, closing with a +discussion "of the inquiry whence the magnet receives the natural virtue +which it has." Peter attributed this virtue to a sympathy with the +heavens, proposing to prove his point by the construction of a +"terrella," a uniform sphere of loadstone which is to be carefully +balanced and mounted in the manner of an armillary sphere, with its axis +directed along the polar axis of the diurnal rotation. He then +continues: + + Now if the stone then move according to the motion of the + heavens, rejoice that you have arrived at a secret marvel. + But if not, let it be ascribed rather to your own want of + skill than to a defect of Nature. But in this position, or + mode of placing, I deem the virtues of this stone to be + properly conserved, and I believe that in other positions + or parts of the sky its virtue is dulled, rather than + preserved. By means of this instrument at all events you + will be relieved from every kind of clock (horologium), + for by it you will be able to know the Ascendant at + whatever hour you will, and all other dispositions of the + heavens which Astrologers seek after. + +It should be noted that the device is to be mounted like an astronomical +instrument and used like one, rather than as a time teller, or as a +simple demonstration of magnetism. In the second part of the _Epistle_ +Peter turns to practical instruments, describing for the first time, the +construction of a magnetic compass consisting of a loadstone or iron +needle pivoted with a casing marked with a scale of degrees. The third +chapter of this section, concluding the _Epistle_, then continues with +the description of a perpetual motion wheel, "elaboured with marvellous +ingenuity, in the pursuit of which invention I have seen many people +wandering about, and wearied with manifold toil. For they did not +observe that they could arrive at the mastery of this by means of the +virtue, or power of this stone." + +This tells us incidentally, that the perpetual motion device was a +subject of considerable interest at this time.[42] Oddly enough, Peter +does not now develop his idea of the terrella, but proceeds to something +quite new, a device (see fig. 22) in which a bar-magnet loadstone is to +be set towards the end of a pivoted radial arm with a circle fitted on +the inside with iron "gear teeth," the teeth being there not to mesh +with others but to draw the magnet from one to the next, a little bead +providing a counterweight to help the inertia of rotation carry the +magnet from one point of attraction to the next. It is by no means the +sort of device that one would naturally evolve as a means of making +magnetism work perpetually, and I suggest that the toothed wheel is +another instance of some vague idea of protoclocks, perhaps that of Su +Sung, being transmitted from the East. + +[Illustration: Figure 22.--MAGNETIC PERPETUAL MOTION WHEEL illustrated +by Peter Peregrinus; from the edition of S. P. Thompson (see footnote +40).] + +The work of Peter Peregrinus is cited by Roger Bacon in his _De +secretis_ as well as in the _Opus majus_ and _Opus minus_. In the first +and earliest of these occurs a description, taken from Ptolemy, of the +construction of the (observing) armillary sphere. He says that this +cannot be made to move naturally by any mathematical device, but "a +faithful and magnificent experimentor is straining to make one out of +such material, and by such a device, that it will revolve naturally with +the diurnal heavenly rotation." He continues with the statement that +this possibility is also suggested by the fact that the motions of +comets, of tides, and of certain planets also follow that of the Sun and +of the heavens. Only in the _Opus minus_, where he repeats reference to +this device, does he finally reveal that it is to be made to work by +means of the loadstone. + +The form of Bacon's reference to Peregrinus is strongly reminiscent of +the statement by Robertus Anglicus, already mentioned as an indication +of preoccupation with diurnally rotating wheels, at a date (1271) +remarkably close to that of the _Epistle_ (1269)--so much so that it +could well be thought that the friend to which Peter was writing was +either Robert himself or somebody associated with him, perhaps at the +University of Paris--a natural place to which the itinerant Peter might +communicate his findings. + +The fundamental question here, of course, is whether the idea of an +automatic astronomical device was transmitted from Arabic, Indian, or +Chinese sources, or whether it arose quite independently in this case as +a natural concomitant of identifying the poles of the magnet with the +poles of the heavens. We shall now attempt to show that the history of +the magnetic compass might provide a quite independent argument in +favour of the hypothesis that there was a 'stimulus' transmission. + + + + +The Magnetic Compass as a Fellow-traveler from China + +The elusive history of the magnetic compass has many points in common +with that of the mechanical clock. Just as we have astronomical models +from the earliest times, so we find knowledge of the loadstone and some +of its properties. Then, parallel to the development of protoclocks in +China throughout the middle ages, we have the evidence analyzed by +Needham, showing the use of the magnet as a divinatory device and of the +(nonmagnetic) south-pointing chariot, which has been confusedly allied +to the story. Curiously, and perhaps significantly the Chinese history +comes to a head at just the same time for compasses and clocks, and a +prime authority for the Chinese compass is Shen Kua (1030-1093) who also +appears in connection with the clock of Su Sung, and who wrote about the +mechanized armillary spheres and other models _ca._ 1086. + +Another similarity occurs in connection with the history of the compass +in medieval Europe. The treatise of Peter Peregrinus, already discussed, +provides the first complete account of the magnetic compass with a +pivoted needle and a circular scale, and this, as we have seen, may be +connected with protoclocks and perpetual-motion devices. There are +several earlier references, however, to the use of the directive +properties of loadstone, mainly for use in navigation, but these +earliest texts have a long history of erroneous interpretation which is +only recently being cleared away. We know now that the famous passages +in the _De naturis rerum_ and _De utensilibus_ of Alexander Neckham[43] +(_ca._ 1187) and a text by Hugues de Berze[44] (after _ca._ 1204) refer +to nothing more than a floating magnet without pivot or scale, but using +a pointer at right angles to the magnet, so that it pointed to the east, +rather than the north or south. A similar method is described (_ca._ +1200) in a poem by Guyot de Provins, and in a history of Jerusalem by +Jacques de Vitry (1215).[45] It is of the greatest interest that, once +more, all the evidence seems to be concentrated in France (Neckham was +teaching in Paris) though at an earlier period than that for the +protoclocks. + +The date might suggest the time of the first great wave of transmissal +of learning from Islam, but it is clear that in this instance, peculiar +for that reason, that Islam learned of the magnetic compass only after +it was already known in the West. In the earliest Persian record, some +anecdotes compiled by al-'Awfiī _ca._ 1230,[46] the instrument used +by the captain during a storm at sea has the form of a piece of hollow +iron, shaped like a fish and made to float on the water after +magnetization by rubbing with a loadstone; the fishlike form is very +significant, for this is distinctly Chinese practice. In a second Muslim +reference, that of Bailak al-Qabājaqī (_ca._ 1282), the ordinary +wet-compass is termed "al-konbas," another indication that it was +foreign to that language and culture.[47] + + +Chronological Chart + +------------------------------------------------------------------------ + + CHINA + + 4th C., B.C. Power gearing + + CLASSICAL EUROPE + + 3rd C., B.C. Archimedes planetarium + 2nd C., B.C. Hipparchus Stereographic Projection + 1st C., B.C. Vitruvius hodometer and water clocks + 65, B.C. (_ca._) Antikythera machine + 1st C., A.D. Hero hodometer and water clocks + 2nd C., A.D. Salzburg and Vosges anaphoric clocks + + CHINA + + 2nd C., A.D. Chang Hêng animated globe hodometer + Continuing tradition of animated astronomical models + 725 Invention of Chinese escapement by I-Hsing and Liang Ling-tsan + + ISLAM + + 807 Harun-al-Rashid + 850 (_ca._) Earliest extant astrolabes + 1000 Geared astrolabe of al-Biruni + + EUROPE + + 1000 Gerbert astronomical model + + ISLAM + + 1025 Equatorium text + + CHINA + + 1074 Shen Kua, clocks and magnetic compass + 1080 Su Sung clock built + 1101 Su Sung clock destroyed + + INDIA + + 1100 (_ca._) Sūrya Siddhānta animated astronomical models + and perpetual motion + 1150 (_ca._) Siddhānta Siromaṇi animated models and perpetual + motion + + ISLAM + + 1150 Saladin clock + + EUROPE + + 1187 Neckham on compass + 1198 Jocelin on water clock + + ISLAM + + 1200 (_ca._) Riḍwān water-clocks, perpetual motion + and weight drive + 1206 al-Jazarī clocks, etc. + 1221 Geared astrolabe + 1232 Charlemagne clock + 1243 al-Konbas (compass) + + EUROPE + + 1245 Villard clocktower, "escapement," perpetual motion + 1267 Villers Abbey clock + 1269 Peregrinus, compass and perpetual motion + 1271 Robertus Anglicus, animated models and "perpetual motion" clock + + ISLAM + + 1272 Alfonsine corpus clock with mercury drum, equatoria + + EUROPE + + 1285 Drover's water clock with wheel and weight drive + 1300 (_ca._) French geared astrolabe + 1320 Richard of Wallingford astronomical clock and equatorium + 1364 de Dondi's astronomical clock with mechanical escapement + later 14th C. Tradition of escapement clocks continues + and degenerates into simple time-keepers +------------------------------------------------------------------------ + +There is therefore reasonable grounds for supporting the medieval +European tradition that the magnetic compass had first come from China, +though one cannot well admit that the first news of it was brought, as +the legend states, by Marco Polo, when he returned home in 1260. There +might well have been another wave of interest, giving the impetus to +Peter Peregrinus at this time, but an earlier transmission, perhaps +along the silk road or by travelers in crusades, must be postulated to +account for the evidence in Europe, _ca._ 1200. The earlier influx does +not play any great part in our main story; it arrived in Europe before +the transmission of astronomy from Islam had got under way sufficiently +to make protoclocks a subject of interest. For a second transmission, we +have already seen how the relevant texts seem to cluster, in France +_ca._ 1270, around a complex in which the protoclocks seem combined with +the ideas of perpetual motion wheels and with new information about the +magnetic compass. + +The point of this paper is that such a complex exists, cutting across +the histories of the clock, the various types of astronomical machines, +and the magnetic compass, and including the origin of "self-moving +wheels." It seems to trace a path extending from China, through India +and through Eastern and Western Islam, ending in Europe in the Middle +Ages. This path is not a simple one, for the various elements make their +appearances in different combinations from place to place, sometimes one +may be dominant, sometimes another may be absent. Only by treating it as +a whole has it been possible to produce the threads of continuity which +will, I hope, make further research possible, circumventing the blind +alleys found in the past and leading eventually to a complete +understanding of the first complicated scientific machines. + + + FOOTNOTES: + + [1] This traditional view is expressed by almost every history + of horology. An ultimate source for many of these has been the + following two classic treatments: J. Beckmann, _A history of + inventions and discoveries_, 4th ed., London, 1846, vol. 1, pp. + 340 ff. A. P. Usher, _A history of mechanical inventions_, 2nd + ed., Harvard University Press. 1954, pp. 191 ff., 304 ff. + + [2] There is a considerable literature dealing with the later + evolution of perpetual motion devices. The most comprehensive + treatment is H. Dircks, _Perpetuum mobile_, London, 1861; 2nd + ser., London, 1870. So far as I know there has not previously + been much discussion of the history of such devices before the + renaissance. + + [3] For the early history of gearing in the West see C. + Matschoss, _Geschichte des Zahnrades_, Berlin, 1940. Also F. M. + Feldhaus, _Die geschichtliche Entwicklung des Zahnrades in + Theorie und Praxis_, Berlin, 1911. + + [4] A general account of these important archaeological objects + will be published by J. Needham, _Science and civilisation in + China_, Cambridge, 1959(?), vol. 4. The original publications + (in Chinese) are as follows: Wang Chen-to, "Investigations and + reproduction in model form of the south-pointing carriage and + hodometer," _National Peiping Academy Historical Journal_, + 1937, vol. 3, p. 1. Liu Hsien-chou, "Chinese inventions in + horological engineering," _Ch'ing-Hua University Engineering + Journal_, 1956, vol. 4, p. 1. + + [5] For illustrations of intermeshing worms in Indian cotton + mills, see Matschoss, _op. cit._ (footnote 3), figs. 5, 6, 7, + p. 7. + + [6] It is interesting to note that the Chinese hodometer was + contemporary with that of Hero and Vitruvius and very similar + in design. There is no evidence whatsoever upon which to decide + whether there may have been a specific transmission of this + invention or even a "stimulus diffusion." + + [7] A summary of the content of the manuscript sources, + illustrated by the original drawings, has been published by H. + Alan Lloyd, _Giovanni de Dondi's horological masterpiece, + 1364_, without date or imprint (?Lausanne, 1955), 23 pp. It + should be remarked that de Dondi declines to describe the + workings of his crown and foliot escapement (though it is well + illustrated) saying that this is of the "common" variety and if + the reader does not understand such simple things he need not + hope to comprehend the complexities of this mighty clock. But + this may be bravado to quite a large degree. + + [8] See, for example, the chronological tables of the 14th + century and the later mentions of clocks in E. Zinner, _Aus der + Frühzeit der Räderuhr_, Munich, 1954, p. 29 ff. Unfortunately + this very complete treatment tends to confuse the factual and + legendary sources prior to the clock of de Dondi; it also + accepts the very doubtful evidence of the "escapement" drawn by + Villard of Honnecourt (see p. 107). An excellent and fully + illustrated account of monumental astronomical clocks + throughout the world is given by Alfred Ungerer, _Les horloges + astronomiques_, Strasbourg, 1931, 514 pp. Available accounts of + the development of the planetarium since the middle ages are + very brief and especially weak on the early history: Helmut + Werner, _From the Aratus globe to the Zeiss planetarium_, + Stuttgart, 1957; C. A. Crommelin, "Planetaria, a historical + survey," _Antiquarian Horology_, 1955, vol. 1, pp. 70-75. + + [9] Derek J. Price, "Clockwork before the clock," _Horological + Journal_, 1955, vol. 97, p. 810, and 1956, vol. 98, p. 31. + + [10] For the use of this material I am indebted to my + co-authors. I must also acknowledge thanks to the Cambridge + University Press, which in the near future will be publishing + our monograph, "Heavenly Clockwork." Some of the findings of + this paper are included in shorter form as background material + for that monograph. A brief account of the discovery of this + material has been published by J. Needham, Wang Ling, and Derek + J. Price, "Chinese astronomical clockwork," _Nature_, 1956, + vol. 177, pp. 600-602. + + [11] For these translations from classical authors I am + indebted to Professor Loren MacKinney and Miss Harriet Lattin, + who had collected them for a history, now abandoned, of + planetariums. I am grateful for the opportunity of giving them + here the mention they deserve. + + [12] A. G. Drachmann, "The plane astrolabe and the anaphoric + clock," _Centaurus_, 1954, vol. 3, pp. 183-189. + + [13] A fuller description of the anaphoric clock and cognate + water-clocks is given by A. G. Drachmann, "Ktesibios, Philon + and Heron," _Acta Historica Scientiarum Naturalium et + Medicinalium_, Copenhagen, 1948, vol. 4. + + [14] First published by O. Benndorf, E. Weiss, and A. Rehm, + _Jahreshefte des österreichischen archäologischen Institut in + Wien_, 1903, vol. 6, pp. 32-49. I have given further details of + its construction in _A history of technology_, ed. Singer, + Holmyard, and Hall, 1957, vol. 3, pp. 604-605. + + [15] L. Maxe-Werly, _Mémoires de la Société Nationale des + Antiquaires de France_, 1887, vol. 48, pp. 170-178. + + [16] The first definitive account of the Antikythera machine + was given by Perikles Rediadis in J. Svoronos, _Das Athener + Nationalmuseum_, Athens, 1908, Textband I, pp. 43-51. Since + then, other photographs (mostly very poor) have appeared, and + an attempt at a reconstruction has been made by Rear Admiral + Jean Theophanidis, _Praktika tes Akademias Athenon_, Athens, + 1934, vol. 9, pp. 140-149 (in French). I am deeply grateful to + the Director of the Athens National Museum, M. Karouzos, for + providing me with an excellent new set of photos, from which + figures 6-8 are now taken. + + [17] H. Diels Über die von Prokop beschriebene Kunstuhr von + Gaza, _Abhandlungen, Akademie der Wissenschaften_, Berlin, + Philos.-Hist. Klasse, 1917, No. 7. + + [18] L. A. Mayer, _Islamic astrolabists and their works_, + Geneva, 1956, p. 62. + + [19] The translation which follows is quoted from J. Beckmann, + _op. cit._ (footnote 1), p. 349. + + [20] E. Wiedemann, "Ein Instrument das die Bewegung von Sonne + und Mond darstellt, nach al Biruni," _Der Islam_, 1913, vol. 4, + p. 5. + + [21] I acknowledge with thanks to the Curator of that museum + the permission to reproduce photographs of this instrument. It + is item 5 in R. T. Gunther, _Astrolabes of the world_, Oxford, + 1932. + + [22] Abulcacim Abnacahm, _Libros del saber_, edition by Rico y + Sinobas, Madrid, 1866, vol. 3, pp. 241-271. The design of the + instrument has been very fully discussed by A. Wegener, "Die + astronomischen Werke Alfons X," _Bibliotheca Mathematica_, + 1905, pp. 129-189. A more complete discussion of the historical + evolution of the equatorium is given in Derek J. Price, _The + equatorie of the planetis_, Cambridge (Eng.), 1955, pp. + 119-133. + + [23] E. Wiedemann, and F. Hauser, "Über die Uhren im Bereich d. + islamischen Kultur," _Nova Acta; Abhandlungen der königliche + Leopoldinisch-Carolinische Deutsche Akademie der Naturforscher + zu Halle_, 1915, vol. 100, no. 5. + + [24] E. Wiedemann, and F. Hauser, _Die Uhr des Archimedes und + zwei andere Vorrichtungen_, Halle, 1918. + + [25] The manuscripts in question are as follows: Gotha, Kat. v. + Pertsch. 3, 18, no. 1348; Oxford, Cod. 954; Leiden, Kat. 3, + 288, no. 1414, Cod. 499 Warn; and another similar, Kat. 3, 291, + no. 1415, Cod. 93 Gol. + + [26] H. Schmeller, Beiträge zur Geschichte der Technik in der + Antike und bei den Arabern, Erlangen, 1922 (_Abhandlungen zur + Geschichte der Naturwissenschaften und der Medizin_ no. 6). + + [27] Once more I am indebted to Professor Loren MacKinney and + Miss Harriet Lattin (see footnote 11) for making their + collections on Gerbert available to me. + + [28] Item 198 in Gunther, _op. cit._ (footnote 21). I am + grateful to the authorities of that museum for permission to + reproduce photographs of this instrument. + + [29] Sotheby and Co., London, sale of March 14, 1957, lot 154. + The outer rim of the rete has 120 teeth. + + [30] The Latin text of the treatise on the Albion, has been + transcribed by Rev. H. Salter and published in R. T. Gunther, + _Early science in Oxford_, Oxford, 1923, vol. 2, pp. 349-370. + An analysis of its design is given in Price, _op. cit._ + (footnote 22), pp. 127-130. + + [31] Such evidence as there is for the existence and form of + the clock is collected by Gunther, _op. cit._ (footnote 30), p. + 49. + + [32] I have discussed this new manuscript source in "Two + medieval texts on astronomical clocks," _Antiquarian Horology_, + 1956, vol. 1, no. 10, p. 156. The manuscript in question is ms. + 230/116, Gonville and Caius College, Cambridge, folios + 11ᵛ-14ᵛ = pp. 31-36. + + [33] _The Chronicle of Jocelin of Brakelond_ ..., H. E. Butler + (ed.), London, 1949, p. 106. + + [34] C. B. Drover, "A medieval monastic water-clock," + _Antiquarian Horology_, 1954, vol. 1, no. 5, pp. 54-58, 63. + Because this water clock uses wheels and strikes bells one must + reject the evidence of literary reference, such as by Dante, + from which the mention of wheels and bells have been taken as + positive proof of the existence of mechanical clocks with + mechanical escapements. The to-and-fro motion of the mechanical + clock escapement is quite an impressive feature, but there + seems to be no literary reference to it before the time of de + Dondi. + + [35] _Annales de la Société Royale d'Archéologie de Bruxelles_, + 1896, vol. 1/8, pp. 203-215, 404-451. The translation here is + cited from Drover, _op. cit._, (footnote 34), p. 56. + + [36] L. Thorndike, _The sphere of Sacrobosco and its + commentators_, Chicago, 1949, pp. 180, 230. + + [37] The album was published with facsimiles by J. B. A. + Lassus, 1858. An English edition with facsimiles of 33 of the + 41 folios was published by Rev. Robert Willis, Oxford, 1859. An + extensive summary of this section is given, with illustrations, + by J. Drummond Robertson, _The evolution of clockwork_, London, + 1931, pp. 11-15. + + [38] M. Jules Quicherat, _Revue Archèologique_, 1849, vol. 6. + + [39] M. C. Frémont. _Origine de l'horloge à poids_, Paris, + 1915. + + [40] For this, I have used and quoted from the very beautiful + edition in English, prepared by Silvanus P. Thompson, London, + Chiswick Press, 1902. + + [41] See E. G. R. Taylor, "The South-pointing needle," _Imago + Mundi_, Leiden, 1951, vol. 8, pp. 1-7 (especially pp. 1, 2). + + [42] I have wondered whether the medieval interest in perpetual + motion could be connected with the use of the "Wheel of + Fortune" in churches as a substitute for bell-ringing on Good + Friday. Unfortunately I can find no evidence for or against the + conjecture. + + [43] W. E. May, "Alexander Neckham and the pivoted compass + needle," _Journal of the Institute of Navigation_, 1955, vol. + 8, no. 3, pp. 283-284. + + [44] W. E. May, "Hugues de Berze and the mariner's compass," + _The Mariner's Mirror_, 1953, vol. 39, no. 2, pp. 103-106. + + [45] H. Balmer, _Beiträge zur Geschichte der Erkenntnis des + Erdmagnetismus_, Aarau, 1956, p. 52. + + [46] The collection is the _Gami 'al Hikajat_; the relevant + passage being given in German translation in Balmer. _op. cit._ + (footnote 45), p. 54. + + [47] Balmer, op. _cit._ (footnote 45), p. 53. + + + +U.S. GOVERNMENT PRINTING OFFICE: 1959 + + + + + + +End of the Project Gutenberg EBook of On the Origin of Clockwork, Perpetual +Motion Devices, and the Compass, by Derek J. de Solla Price + +*** END OF THIS PROJECT GUTENBERG EBOOK ON THE ORIGIN OF CLOCKWORK *** + +***** This file should be named 30001-0.txt or 30001-0.zip ***** +This and all associated files of various formats will be found in: + https://www.gutenberg.org/3/0/0/0/30001/ + +Produced by Chris Curnow, Turgut Dincer, Joseph Cooper and +the Online Distributed Proofreading Team at +https://www.pgdp.net. + + +Updated editions will replace the previous one--the old editions +will be renamed. + +Creating the works from public domain print editions means that no +one owns a United States copyright in these works, so the Foundation +(and you!) can copy and distribute it in the United States without +permission and without paying copyright royalties. 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