diff options
Diffstat (limited to '30001-h/30001-h.htm')
| -rw-r--r-- | 30001-h/30001-h.htm | 2697 |
1 files changed, 2697 insertions, 0 deletions
diff --git a/30001-h/30001-h.htm b/30001-h/30001-h.htm new file mode 100644 index 0000000..cf3e159 --- /dev/null +++ b/30001-h/30001-h.htm @@ -0,0 +1,2697 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" +"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> +<html xmlns="http://www.w3.org/1999/xhtml"> +<head> +<meta name="generator" content="HTML Tidy, see www.w3.org" /> +<meta http-equiv="Content-Type" content= +"text/html;charset=UTF-8" /> +<title>The Project Gutenberg eBook of On the Origin of Clockwork, +Perpetual Motion Devices and the Compass by Derek J. de Solla Price</title> +<style type="text/css"> + + p { margin-top: .75em; + text-align: justify; + margin-bottom: .75em;} + + p.tb { margin-top: 1.5em; + text-align: justify; + margin-bottom: .75em;} + + p.indent { margin-top: 0em; margin-bottom: 0em; + text-align: justify; margin-left: 3.5em; text-indent: -3.5em;} + + p.title { margin-top: 1.25em; + text-align: justify; + margin-bottom: .75em;} + + + p.quotsig { margin-top: .75em; + text-align: right; + margin-bottom: .75em;} + + h1,h2,h3,h4,h5,h6 { + text-align: center; /* all headings centered */ + clear: both; font-weight: normal; + margin-top: 1.5em; + margin-bottom: .75em; } + + + + /* sup, + sub { + height: 0em; font-size: .7em; + vertical-align: baseline; + position: relative; }*/ + + sup { bottom: .2em; font-size: .7em; margin-left: 0em;; } + + sub { top: 0em; font-size: .6em; } + + hr { width: 33%; + margin-top: 0em; + margin-bottom: 0em; + margin-left: auto; + margin-right: auto; + clear: both; + } + + + table {margin-left: auto; margin-right: auto;} + + + td.td100 {padding-right: 1em; padding-left: 0em; padding-top: 0em; padding-bottom: 0em; font-size: .9em; text-align: justify; width: 100%; vertical-align: top; } + td.td100c {padding-right: 0em; padding-left: 2.4em; padding-top: 1em; padding-bottom: .5em; font-size: 1em; text-align: left; width: 100%; vertical-align: middle;} + td.right {padding-top: .2em; padding-bottom: .2em; font-size: .8em; text-align: right; width: 10%; vertical-align: bottom;} + td.left {padding-top: .2em; padding-bottom: .2em; font-size: .8em; text-align: right; width: 90%; vertical-align: top;} + td.center {padding-top: .2em; padding-bottom: .2em; font-size: 1em; text-align: center; width: 50%; vertical-align: top;} + td.left100 {padding-right: 2em; padding-left: 2em; padding-top: .2em; padding-bottom: .2em; font-size: 1em; text-align: left; width: 100%; vertical-align: top;} + + body {margin-left: 10%; margin-right: 10%; + } + + .pagenum { /* uncomment the next line for invisible page numbers */ + /* visibility: hidden; */ + position: absolute; + right: 3%; font-style: normal; + font-size: .8em; + text-align: right; + } /* page numbers */ + .tn {font-size: .8em; width: 80%; background-color: #EEE; padding: 0.5em 1em 0.5em 1em; text-align: justify;} + + + .blockquot {font-size: .85em; margin-top: 1.5em; margin-bottom: 1.5em; } + + .blockquot2 {font-size: .83em; margin-top: 1.5em; margin-bottom: 1.5em; + margin-left: 20%;} + + img {text-decoration: none; border: none; margin-bottom: 0em; margin-top: 0em;} + img.floatLeft {float: left; height: 2.2em; margin-right: 0em; border: none;} + + + .smcap {font-variant: small-caps;} + .u {text-decoration: underline;} + + .caption {font-size: .85em; text-align: justify; margin-top: 1em; + margin-bottom: 2em; margin-left: 5%; margin-right: 5%; } + .caption2 {font-size: .85em; text-align: justify; margin-top: 1em; + margin-bottom: 2em; margin-left: 5%; margin-right: 5%; } + + .figcenter {margin: auto; text-align: center;} + + + .footnotes {border: none;} + .footnote {margin-left: 10%; margin-right: 5%; font-size: 0.9em;} + .footnote .label {position: absolute; right: 84%; text-align: right; font-size: .9em;} + .fnanchor {vertical-align: super; font-size: .7em; text-decoration: none;} + + +</style> +</head> +<body> +<div>*** START OF THE PROJECT GUTENBERG EBOOK 30001 ***</div> + +<h6> </h6> + +<div class="tn"> +Transcriber's note:<br /><br /> +The original three column Chronological Table +has been replaced by a single column table +with the same chronological order to make its reading easier +at all browser settings. +</div> + +<h6> </h6> + +<div class="figcenter" style="width: 500px;"><img src="images/cover.jpg" width="500" height="647" alt= +"Cover" title="Cover page" /></div> + +<p><span class='pagenum'>81</span></p> + +<p class="quotsig"><span class="smcap">Contributions from<br /> +The Museum of History and Technology:<br /> +Paper 6</span><br /><br /></p> + +<p class="quotsig"><span class="smcap">On the Origin of Clockwork,<br /> +Perpetual Motion Devices, and the Compass</span><br /> +<i>Derek J. de Solla Price</i><br /><br /></p> + +<table width="100%" summary="TOC"> + +<tr> +<td class="left">POWER AND MOTION GEARING</td> +<td class="right"><a href="#Page_83a">83</a></td> +</tr> + +<tr> +<td class="left">MECHANICAL CLOCKS</td> +<td class="right"><a href="#Page_84a">84</a></td> +</tr> + +<tr> +<td class="left">PERPETUAL MOTION AND THE CLOCK BEFORE DE DONDI</td> +<td class="right"><a href="#Page_108a">108</a></td> +</tr> + +<tr> +<td class="left">THE MAGNETIC COMPASS AS A FELLOW-TRAVELER FROM CHINA</td> +<td class="right"><a href="#Page_110a">110</a></td> +</tr> +</table> + +<p><span class='pagenum'>82</span><br /><br /></p> + +<h2><i>ON THE ORIGIN OF CLOCKWORK,<br /> +PERPETUAL MOTION DEVICES<br /> +AND THE COMPASS</i></h2> + +<h3><i>By Derek J. de Solla Price</i></h3> + +<table width="80%" summary="intro"> + +<tr> +<td><p><i>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.</i></p> + +<p><i>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.</i></p> + +<p><span class="smcap">The Author</span>: <i>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.</i></p></td> +</tr> + +</table> + +<div class="blockquot2"><p>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. (<i>Sūrya Siddhānta</i>, ed. Burgess, xiii, +18-19.)</p></div> + +<p><img src="images/cap_t.png" class="floatLeft" alt="T" />HE 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.</p> + +<p>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.<a name="FNanchor_1" id="FNanchor_1"></a><a href="#Footnote_1" class="fnanchor">1</a> 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.</p> + +<p>Furthermore, even if one admits the use of clocklike +gearing before the existence of the clock, it is still +<span class='pagenum'>83</span>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, <i>ca.</i> 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, <i>ca.</i> 1272.</p> + +<p>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 +<i>Perpetuum Mobile</i>, 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.<a name="FNanchor_2" id="FNanchor_2"></a><a href="#Footnote_2" class="fnanchor">2</a> 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.</p> + +<div class="figcenter" style="width: 500px;"><a name="fig_1" id="fig_1" /><img src="images/fig_1.jpg" width="500" height="666" alt= +"Framework Structure of the Astronomical +Clock of Giovanni de Dondi of Padua, +A.D. 1364." title="" /> + +<div class="caption">Figure 1.—<span class="smcap">Framework Structure of the Astronomical +Clock</span> of Giovanni de Dondi of Padua, +A.D. 1364.</div></div> + + +<h3><a name="Page_83a" id="Page_83a">Power and Motion Gearing</a></h3> + +<p>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.),<a name="FNanchor_3" id="FNanchor_3"></a><a href="#Footnote_3" class="fnanchor">3</a> and in China actual examples of wheels +and moulds for wheels dating from the 4th century +<span class='pagenum'>84</span>B.C. have been preserved.<a name="FNanchor_4" id="FNanchor_4"></a><a href="#Footnote_4" class="fnanchor">4</a> 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.<a name="FNanchor_5" id="FNanchor_5"></a><a href="#Footnote_5" class="fnanchor">5</a> 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.<br /><br /></p> + +<div class="figcenter" style="width: 500px;"><a name="fig_2" id="fig_2" /><img src="images/fig_2.jpg" width="500" height="497" alt= +"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." title="" /> + +<div class="caption">Figure 2.—<span class="smcap">Astronomical Clock</span> 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.</div></div> + + +<p>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.<a name="FNanchor_6" id="FNanchor_6"></a><a href="#Footnote_6" class="fnanchor">6</a> One may also cite +the use of the reduction gear chain in power machinery +as used in the geared windlass of Archimedes and +Hero.</p> + +<p>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.</p> + + +<h3><a name="Page_84a" id="Page_84a">Mechanical Clocks</a></h3> + +<p>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 me<span class='pagenum'>85</span>chanical clocks has demonstrated certain peculiarities +most relevant to our present argument.</p> + + +<p class="title"><span class="smcap">the european tradition</span></p> + +<p>If one is to establish a <i>terminus ante quem</i> 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,<a name="FNanchor_7" id="FNanchor_7"></a><a href="#Footnote_7" class="fnanchor">7</a> 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 <i>horologium</i> and its vernacular equivalents.</p> + +<p>Temporarily postponing the consideration of evidence +prior to <i>ca.</i> 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.<a name="FNanchor_8" id="FNanchor_8"></a><a href="#Footnote_8" class="fnanchor">8</a> 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 (<i>ca.</i> 1475), +pendulum control (<i>ca.</i> 1650), and the anchor escapement +(<i>ca.</i> 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.<br /><br /></p> + +<div class="figcenter" style="width: 500px;"><img src="images/fig_3.jpg" width="500" height="916" alt= +"Figure 3.—German Wall Clock, Probably About +1450, showing the degeneration in complexity from +that of de Dondi's clock." title="" /> + +<div class="caption">Figure 3.—<span class="smcap">German Wall Clock, Probably About +1450</span>, showing the degeneration in complexity from +that of de Dondi's clock.</div></div> + +<p><span class='pagenum'>86</span></p> + +<p>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. <a href="#fig_1">1,</a> <a href="#fig_2">2</a>) +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.</p> + +<p>On the basis of such evidence I have suggested elsewhere<a name="FNanchor_9" id="FNanchor_9"></a><a href="#Footnote_9" class="fnanchor">9</a> +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.</p> + +<p>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 +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.</p> + + +<p class="title"><span class="smcap">the chinese tradition</span></p> + +<p>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.<a name="FNanchor_10" id="FNanchor_10"></a><a href="#Footnote_10" class="fnanchor">10</a> 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 H&ecirc;ng <i>ca.</i> 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 H&ecirc;ng +onwards, largely independent of any transmissions +from the West.</p> + +<p>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 (<i>e.g.</i>, equator, ecliptic, meridians, etc.), or a +solid celestial globe on which such circles could be +drawn, together with the constellations of the fixed +<span class='pagenum'>87</span>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.</p> + +<p>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."</p> + +<p>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.</p> + +<p>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.</p> + +<p>In its final form, as built by Su Sung after many +trials and improvements, the Chinese "astronomical +clocktower" 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. <a href="#fig_4">4</a>). 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.</p> + +<p>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.</p> + +<p>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" (<i>glokke</i>). 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<span class='pagenum'>88</span> +European clocks should have prompted them to +open their doors, previously so carefully and for +so long kept closed against the foreign barbarians.</p> + + +<div class="figcenter" style="width: 500px;"><a name="fig_4" id="fig_4" /><a href="images/fig_4_zoom.jpg"><img src="images/fig_4.jpg" width="500" height="516" alt= +"Astronomical Clock Tower of Su +Sung in K'ai-feng, ca. A.D. 1090." title="Click for detailed image" /></a> + +<div class="caption">Figure 4.—<span class="smcap">Astronomical Clock Tower of Su +Sung</span> in K'ai-feng, <i>ca.</i> A.D. 1090, from an original +drawing by John Christiansen. (<i>Courtesy of Cambridge +University Press.</i>)</div></div> + +<h3>Mechanized Astronomical Models</h3> + +<p>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.</p> + +<p><span class='pagenum'>89</span></p> + +<p class="title"><span class="smcap">hellenistic period</span></p> + +<p>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.<a name="FNanchor_11" id="FNanchor_11"></a><a href="#Footnote_11" class="fnanchor">11</a></p> + +<p>Cicero's descriptions of Archimedes' planetarium +are (italics supplied):</p> + +<div class="blockquot"><p>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>i. e.</i>, 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>i.e.</i>, set in motion] the globe, it was actually true +that the moon was always as many revolutions behind the +sun on the <i>bronze</i> 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].</p> + +<p class="quotsig"> +<i>De republica</i>, I, xiv (21-22), Keyes' translation. +</p> + +<p class="tb">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.</p> + +<p class="quotsig"> +<i>Tusculanae disputationes</i>, I, 63. +</p> +</div> + +<p class="tb">Later descriptions from Ovid, Lactantius, Claudian, +Sextus Empiricus, and Pappus, respectively, are +(italics supplied):</p> + +<div class="blockquot"><p>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>i. e.</i>, the outer bronze +globe's] round form. The form of the temple [of Vesta] +is similar....</p> + +<p class="quotsig"> +Ovid, <i>Fasti</i> (1st century, A.D.), VI, 277-280, +Frazer's translation. +</p> + +<p class="tb">The Sicilian Archimedes, was able to make a reproduction +and model of the world in concave <i>brass</i> (concavo aere +similitudinem mundi ac figuram); in it he so arranged +the <i>sun</i> and <i>moon</i> 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 <i>courses of +the stars</i>, whether fixed or wandering.</p> + +<p class="quotsig"> +Lactantius, <i>Institutiones divinae</i> (4th century, A.D.), II, 5, 18. +</p> + +<p class="tb">Archimedes' sphere. When Jove looked down and saw +the heavens figured in a sphere of <i>glass</i>, 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 <i>stars</i> and actuates the lifelike mass with +definite motions. A false <i>zodiac</i> runs through a year of its +own and a toy <i>moon</i> waxes and wanes month by month. +Now bold invention rejoices to make its own heaven revolve +and sets the <i>stars</i> [planets?] in motion by human wit....</p> + +<p class="quotsig"> +Claudian, <i>Carmina minora</i> (<i>ca.</i> A.D. 400), LI (LXVIII), +Platnaure's translation.<br /> +</p> + +<p class="tb">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 <i>wood</i>, or at the movements +of these [bodies], but by the devices and causes of the +movements.</p> + +<p class="quotsig"> +Sextus Empiricus, <i>Adversus mathematicos</i> (3rd century, A.D.), +IX, 115, Epps' translation. +</p></div> + +<p><span class='pagenum'>90</span></p> + +<div class="blockquot"><p> +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 <i>water</i>, and Archimedes the Syracusan, according +to some, knows the cause and reasons for all of these.</p> + +<p class="quotsig"> +Pappus (3rd century, A.D.), <i>Works</i> (Hultsch edition), +VIII, 2, Epps' translation. +</p></div> + +<p>A similar arrangement seems to be indicated in +another mechanized globe, also mentioned by Cicero +and said to have been made by Posidonius:</p> + +<div class="blockquot"><p>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 <i>sun</i> and <i>moon</i> and +<i>five</i> 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....</p> + +<p class="quotsig"> +<i>De natura deorum</i>, II, xxxiv-xxxv (88), +Yonge's translation. +</p></div> + +<p>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 H&ecirc;ng. 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.</p> + +<p class="tb">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:</p> + +<div class="blockquot"><p>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.</p> + +<p class="quotsig"> +<i>Pneumatics</i>, XLVI, Woodcroft's translation. +</p></div> + +<p>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.</p> + +<p>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.</p> + +<p>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 (<i>ca.</i> A.D. 120) +it had led to the successive inventions of the anaphoric +clock and of the planispheric astrolabe.<a name="FNanchor_12" id="FNanchor_12"></a><a href="#Footnote_12" class="fnanchor">12</a> 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.</p> + +<p>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.<a name="FNanchor_13" id="FNanchor_13"></a><a href="#Footnote_13" class="fnanchor">13</a><br /><br /></p> + +<p><span class='pagenum'>91</span></p> + +<div class="figcenter" style="width: 500px;"><a name="fig_5" id="fig_5" /><img src="images/fig_5.jpg" width="500" height="596" alt= +"Plate of Salzburg +Anaphoric Clock," title="" /> + +<div class="caption">Figure 5. <span class="smcap">Plate of Salzburg +Anaphoric Clock</span>, a reconstruction +(see footnote <a href="#Footnote_14">14</a>) based on +a photograph of the remaining +fragment. (<i>Courtesy of Oxford +University Press.</i>)</div></div> + + +<p>Parts of two such discs from anaphoric clocks +have been found, one at Salzburg<a name="FNanchor_14" id="FNanchor_14"></a><a href="#Footnote_14" class="fnanchor">14</a> and one at +Grand in the Vosges,<a name="FNanchor_15" id="FNanchor_15"></a><a href="#Footnote_15" class="fnanchor">15</a> 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. <a href="#fig_5">5</a>). +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.</p> + +<p>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-<span class='pagenum'>92</span>keeping clocks before the change was made to a +fixed dial and moving hand.</p> + +<p>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.<a name="FNanchor_16" id="FNanchor_16"></a><a href="#Footnote_16" class="fnanchor">16</a> 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.</p> + +<p>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 <i>ca.</i> 65 B.C. &plusmn;10 years, and we can be sure +that the machine is of Hellenistic origin, possibly from +Rhodes or Cos.</p> + +<div class="figcenter" style="width: 500px;"><a name="fig_6" id="fig_6" /><img src="images/fig_6.jpg" width="500" height="301" alt= +"Antikythera Machine, Largest Fragment." title="" /> + +<div class="caption">Figure 6.—<span class="smcap">Antikythera Machine, Largest Fragment.</span> +(<i>Photo courtesy of National Museum, Athens.</i>)</div></div> + +<p>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. <a href="#fig_6">6</a>) 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. <a href="#fig_7">7</a>, 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. <a href="#fig_7">7</a>, +top) has a pair of rings carefully engraved and graduated<span class='pagenum'>93</span> +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&deg; in the 45&deg; present).</p> + +<div class="figcenter" style="width: 500px;"><a name="fig_7" id="fig_7" /><img src="images/fig_7.jpg" width="500" height="459" alt= +"Antikythera Machine, Two Smaller +Fragments." title="" /> + +<div class="caption">Figure 7.—<span class="smcap">Antikythera Machine, Two Smaller +Fragments.</span> (<i>Photo courtesy of National Museum, +Athens.</i>)</div></div> + +<p>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.</p> + +<p>Some technical details can be gleaned however. +The shape of the gear teeth appears to be almost +exactly equilateral triangles in all cases (fig. <a href="#fig_8">8</a>), 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. <a href="#fig_9">9</a>) has shown that the appearances +are consistent with the theory that the<span class='pagenum'>94</span> +purpose of the gears was to provide the correct angular +ratios to move the sun and planets at their appropriate +relative speeds.</p> + +<div class="figcenter" style="width: 500px;"><a name="fig_8" id="fig_8" /><img src="images/fig_8.jpg" width="500" height="490" alt= +"Antikythera Machine, +Detail From Figure 6 +showing gearing." title="" /> + +<div class="caption">Figure 8.—<span class="smcap">Antikythera Machine, +Detail From Figure 6</span>, +showing gearing. (<i>Photo courtesy +of National Museum, Athens.</i>)</div></div> + +<p>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.<br /><br /></p> + +<table width="100%" summary="note" border="1"> +<tr><td class="left100"> +<div class="blockquot"><p><i>Note added in proof</i>:</p> + +<p>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 <i>Scientific American</i>, 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.</p></div> +</td></tr> +</table> + +<p class="tb">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<span class='pagenum'>95</span> +are more akin to those current in China than in the +West. The relevant portions of text are as follows +(italics supplied):</p> + +<div class="blockquot"><p>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.</p> + +<p class="quotsig"> +<i>Sūrya Siddhānta</i>, xiii, 15-22,<br /> +E. Burgess' translation, New Haven, 1860. +</p> + +<div class="figcenter" style="width: 500px;"><a name="fig_9" id="fig_9" /><img src="images/fig_9.jpg" width="500" height="563" alt= +"Antikythera Machine, Partial Reconstruction +by Theophanidis." title="" /> + +<div class="caption">Figure 9.—<span class="smcap">Antikythera Machine, Partial Reconstruction +by Theophanidis</span> (see footnote <a href="#Footnote_16">16</a>).</div></div> + +<p>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.</p> + +<p>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 + +<span class='pagenum'>96</span> + +the orifice left open for filling the wheel. The wheel will +then revolve of itself, drawn around by the water.</p> + +<p>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.</p> + +<p>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.</p> + +<p>The self-revolving machine [mentioned by <i>Lalla</i>, 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.</p> + +<p>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.</p> + +<p class="quotsig"> +<i>Siddhānta Siromaṇi</i>, xi, 50-57, L. Wilkinson's translation,<br /> +revised by Bȧpu̇ deva S(h)ȧstri, Calcutta, 1861. +</p></div> + +<p>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 <i>Sūrya Siddhānta</i> is known to date, in +its original form, from the early Middle Ages, <i>ca.</i> 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 <i>ca.</i> 1000 to <i>ca.</i> +1150 A.D. The date of the <i>Siddhānta Siromaṇi</i> 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 +clocktower made by Su Sung. The technical details +will lead us to suppose there is more than a temporal +connection.</p> + +<p>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.</p> + +<p>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 <i>Sūrya Siddhānta</i>, of the "wonder-causing +instrument" to which mercury must be +applied.</p> + +<p>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.</p> + +<p>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.</p> + +<p>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 <i>ca.</i> 535) describes a monumental +water clock which was erected in Gaza <i>ca.</i> 500.<a name="FNanchor_17" id="FNanchor_17"></a><a href="#Footnote_17" class="fnanchor">17</a> It +contained impressive jackwork, such as a Medusa +<span class='pagenum'>97</span> +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.</p> + +<p>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 (<i>ca.</i> 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,<a name="FNanchor_18" id="FNanchor_18"></a><a href="#Footnote_18" class="fnanchor">18</a> 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.</p> + +<p>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:<a name="FNanchor_19" id="FNanchor_19"></a><a href="#Footnote_19" class="fnanchor">19</a></p> + +<div class="blockquot"><p>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. +</p></div> + +<p>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.</p> + +<div class="figcenter" style="width: 500px;"><a name="fig_10" id="fig_10" /><img src="images/fig_10.jpg" width="500" height="518" alt= +"Calendrical Gearing Designed by +al-Biruni." title="" /> + +<div class="caption">Figure 10.—<span class="smcap">Calendrical Gearing Designed by +al-Biruni</span>, <i>ca.</i> 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 <a href="#Footnote_20">20</a>).</div></div> + +<p>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 (<i>ca.</i> 1000)—significantly, +perhaps, he is well known for his travel +account of India—there is remarkable innovation.</p> + +<p>Most cogent to our purpose is a text, described for +the first time by Wiedemann,<a name="FNanchor_20" id="FNanchor_20"></a><a href="#Footnote_20" class="fnanchor">20</a> in which al-Biruni +<span class='pagenum'>98</span>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 (<i>e.g.</i>, 7, 19, 59) as dictated by the astronomical +constants involved (see fig. <a href="#fig_10">10</a>). 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 <i>Farās</i> 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.</p> + +<div class="figcenter" style="width: 500px;"><img src="images/fig_11.jpg" width="500" height="440" alt= +"Geared Astrolabe by Muḥammad b. Abī Bakr of Isfahan, A.D. 1221-1222." title="" /> + +<div class="caption">Figure 11.—<span class="smcap">Geared Astrolabe by Muḥammad b. Abī Bakr of Isfahan</span>, A.D. 1221-1222. +(<i>Photo courtesy of Science Museum, London.</i>)</div></div> + +<p>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.</p> + +<p><span class='pagenum'>99</span></p> + +<div class="figcenter" style="width: 500px;"><img src="images/fig_12.jpg" width="500" height="517" alt= +"Gearing from Astrolabe Shown in Figure 11." title="" /> + +<div class="caption">Figure 12.—<span class="smcap">Gearing from Astrolabe Shown in Figure 11.</span> 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. (<i>Photo courtesy of Science Museum, London.</i>)</div></div> + +<p>This landmark in the history of science and technology +is now preserved at the Museum of the +History of Science, Oxford, England.<a name="FNanchor_21" id="FNanchor_21"></a><a href="#Footnote_21" class="fnanchor">21</a> 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 +<span class='pagenum'>100</span>much easier to mark out geometrically (<i>e.g.</i>, 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.<br /><br /></p> + +<div class="figcenter" style="width: 500px;"><a name="fig_13" id="fig_13" /><img src="images/fig_13.jpg" width="500" height="351" alt= +"Astrolabe Clock, Regulated by a +Mercury Drum." title="" /> + +<div class="caption">Figure 13.—<span class="smcap">Astrolabe Clock, Regulated by a +Mercury Drum</span>, from the Alfonsine <i>Libros del saber</i> +(see footnote <a href="#Footnote_22">22</a>).</div></div> + +<p>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 (<i>ca.</i> 450), but the +first general, though crude, planetary equatorium +seems to have been described by Abulcacim Abnacahm +(<i>ca.</i> 1025) in Granada; it has been handed down +to us in the archaic Castilian of the Alfonsine <i>Libros +del saber</i>.<a name="FNanchor_22" id="FNanchor_22"></a><a href="#Footnote_22" class="fnanchor">22</a> The sections of this book, dealing with the +<i>Laminas de las VII Planetas</i>, describe not only this +instrument but also the improved modification introduced +by Azarchiel (born <i>ca.</i> 1029, died <i>ca.</i> 1087).</p> + +<p>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 (<i>ca.</i> 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.</p> + +<p>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<span class='pagenum'>101</span> 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 +<i>ca.</i> 1276-77.</p> + +<table width="100%" summary="perpetual wheels" border="0"> +<tr><td class="center"> +<div class="figcenter" style="width: 200px;"><a name="fig_14" id="fig_14" /><img src="images/fig_14.jpg" width="200" height="195" alt= +"Islamic Perpetual Motion Wheel." title="" /></div> + +<div class="caption2">Figure 14.—<span class="smcap">Islamic Perpetual Motion Wheel</span>, +after manuscript cited by Schmeller (see footnote <a href="#Footnote_26">26</a>).</div> +</td> +<td class="center"> +<div class="figcenter" style="width: 204px;"><img src="images/fig_15.jpg" width="204" height="195" alt= +"Another Perpetual Motion Wheel." title="" /></div> + +<div class="caption2">Figure 15.—<span class="smcap">Another Perpetual Motion Wheel</span>, +after the text cited in figure 14.</div> +</td></tr> +</table> + +<p>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. <a href="#fig_13">13</a>). +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.</p> + +<p>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.</p> + + +<p>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.<a name="FNanchor_23" id="FNanchor_23"></a><a href="#Footnote_23" class="fnanchor">23</a> Other Islamic texts give versions +of the water clocks and automata of Archimedes and +of Hero and Philo of Alexandria.<a name="FNanchor_24" id="FNanchor_24"></a><a href="#Footnote_24" class="fnanchor">24</a> In at least three +cases<a name="FNanchor_25" id="FNanchor_25"></a><a href="#Footnote_25" class="fnanchor">25</a> 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.<a name="FNanchor_26" id="FNanchor_26"></a><a href="#Footnote_26" class="fnanchor">26</a> + +<span class='pagenum'>102</span> + +The devices include a many chambered wheel (see fig. <a href="#fig_14">14</a>) 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. <a href="#fig_16">16</a>); +perhaps for balance, the whole arrangement is made +in duplicate with common axles for the corresponding +parts.</p> + +<div class="figcenter" style="width: 500px;"><a name="fig_16" id="fig_16" /><img src="images/fig_16.jpg" width="500" height="273" alt= +"Islamic Pump Powered by a Weight Drive." title="" /> + +<div class="caption">Figure 16.—<span class="smcap">Islamic Pump Powered by a Weight Drive</span>, after the text cited in figure 14.</div></div> + +<p>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.</p> + + +<p class="title"><span class="smcap">medieval europe</span></p> + +<p>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 <i>ca.</i> 1292), +there are occasional references to the most primitive +mechanized "visual aids" in astronomy.</p> + +<p>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:<a name="FNanchor_27" id="FNanchor_27"></a><a href="#Footnote_27" class="fnanchor">27</a></p> + +<div class="blockquot"><p>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 +<span class='pagenum'>103</span> +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.</p></div> + +<p>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.</p> + +<p>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.</p> + +<p>The geared astrolabe of al-Biruni is another type of +protoclock to have been transmitted. A specimen in +the Science Museum, London,<a name="FNanchor_28" id="FNanchor_28"></a><a href="#Footnote_28" class="fnanchor">28</a> 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. <a href="#fig_17">17</a> and <a href="#fig_18">18</a>). 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 <i>ca.</i> 1300. Another +Gothic astrolabe with a similar gear ring on the rete, +said to date from <i>ca.</i> 1400 (it could well be much +earlier) is now in the Billmeier collection (London).<a name="FNanchor_29" id="FNanchor_29"></a><a href="#Footnote_29" class="fnanchor">29</a></p> + +<p>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.<a name="FNanchor_30" id="FNanchor_30"></a><a href="#Footnote_30" class="fnanchor">30</a> Nevertheless it is evidently a normal +manually operated device like all the others. In +addition to this instrument, Richard is said to have +constructed <i>ca.</i> 1320, a fine planetary clock for his +Abbey.<a name="FNanchor_31" id="FNanchor_31"></a><a href="#Footnote_31" class="fnanchor">31</a> 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>i.e.</i>, 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.<br /><br /></p> + +<p><span class='pagenum'>104</span></p> + +<div class="figcenter" style="width: 500px;"><a name="fig_17" id="fig_17" /><img src="images/fig_17.jpg" width="500" height="668" alt= +"French Geared Astrolabe of Trefoil Gothic Design." title="" /> + +<div class="caption">Figure 17.—<span class="smcap">French Geared Astrolabe of Trefoil Gothic Design</span>, <i>ca.</i> 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. (<i>Photo courtesy of Science Museum. +London.</i>)</div></div> + +<div class="figcenter" style="width: 500px;"><a name="fig_18" id="fig_18" /><img src="images/fig_18.jpg" width="500" height="221" alt= +"Gear Train Of Pointer in figure 17." title="" /> + +<div class="caption">Figure 18.—<span class="smcap">Gear Train Of +Pointer</span> in figure 17. (<i>Photo +courtesy of Science Museum, London.</i>)</div></div> + + +<p>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 <i>ca.</i> 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.<a name="FNanchor_32" id="FNanchor_32"></a><a href="#Footnote_32" class="fnanchor">32</a> Now a geared version of the + +<span class='pagenum'>105</span> + +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, <i>ca.</i> 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 +<i>ca.</i> 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.</p> + +<p>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.<a name="FNanchor_33" id="FNanchor_33"></a><a href="#Footnote_33" class="fnanchor">33</a> 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.</p> + +<p>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 <i>ca,</i> 1285, had become more complex +and were rather similar in appearance to the Alfonsine +mercury drum.<a name="FNanchor_34" id="FNanchor_34"></a><a href="#Footnote_34" class="fnanchor">34</a> The illustration (fig. <a href="#fig_19">19</a>) 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.</p> + +<p><span class='pagenum'>106</span></p> + +<p>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;<a name="FNanchor_35" id="FNanchor_35"></a><a href="#Footnote_35" class="fnanchor">35</a> 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.</p> + +<div class="blockquot"><p>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.</p></div> + +<p>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:<a name="FNanchor_36" id="FNanchor_36"></a><a href="#Footnote_36" class="fnanchor">36</a></p> + +<div class="blockquot"><p>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.</p></div> + +<div class="figcenter" style="width: 500px;"><a name="fig_19" id="fig_19" /><img src="images/fig_19.jpg" width="500" height="559" alt= +"Manuscript Illumination of a Medieval +Waterclock." title="" /> + +<div class="caption">Figure 19.—<span class="smcap">Manuscript Illumination of a Medieval +Waterclock</span>, showing a partitioned wheel, a +weight drive, and a carillion for striking. From +Drover (see footnote <a href="#Footnote_34">34</a>).</div></div> + +<p>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 <i>terminus post quem</i> +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.</p> + +<p><span class='pagenum'>107</span></p> + +<div class="figcenter" style="width: 400px;"><a name="fig_20" id="fig_20" /><img src="images/fig_20.jpg" width="400" height="418" alt= +"Arrangement for Turning a Figure +Of an Angel." title="" /> + +<div class="caption">Figure 20.—<span class="smcap">Arrangement for Turning a Figure +Of an Angel.</span> It has been alleged that this drawing +by Villard represents an escapement. After Lassus +(see footnote <a href="#Footnote_37">37</a>).</div></div> + +<p>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.<a name="FNanchor_37" id="FNanchor_37"></a><a href="#Footnote_37" class="fnanchor">37</a> +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. <a href="#fig_20">20</a>), 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.</p> + +<p>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 <i>ca.</i> 1285.</p> + +<p>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,<a name="FNanchor_38" id="FNanchor_38"></a><a href="#Footnote_38" class="fnanchor">38</a> 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.</p> + +<p>A quite different interpretation has been suggested +by Fr&eacute;mont;<a name="FNanchor_39" id="FNanchor_39"></a><a href="#Footnote_39" class="fnanchor">39</a> he believes that the wheel may have +acted as a fly-wheel and the ropes and counterpoises, +<span class='pagenum'>108</span>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 Fr&eacute;mont, 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.</p> + +<div class="figcenter" style="width: 400px;"><a name="fig_21" id="fig_21" /><img src="images/fig_21.jpg" width="400" height="434" alt= +"Villard's Perpetual Motion Wheel." title="" /> + +<div class="caption">Figure 21.—<span class="smcap">Villard's Perpetual Motion Wheel</span>, +from Lassus (see footnote <a href="#Footnote_37">37</a>).</div></div> + +<p>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. <a href="#fig_21">21</a>) 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.</p> + +<p>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.</p> + +<h3><a name="Page_108a" id="Page_108a">Perpetual Motion and the Clock before +de Dondi</a></h3> + +<p>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 <i>ca.</i> 1150 or a little +earlier, as those of Riḍwān <i>ca.</i> 1200, that of the +Alfonsine mercury clock, <i>ca.</i> 1272, and the French +Bible illumination of <i>ca.</i> 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, <i>ca.</i> 1100, and possibly reinforced +by further transmissions at later dates.</p> + +<p>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.</p> + +<p>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 <i>Epistle on the magnet</i>, written by +Peter Peregrinus, a Picard, in an army camp at the +Siege of Lucera and dated August 8, 1269.<a name="FNanchor_40" id="FNanchor_40"></a><a href="#Footnote_40" class="fnanchor">40</a> 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 <i>ca.</i> 1250.<a name="FNanchor_41" id="FNanchor_41"></a><a href="#Footnote_41" class="fnanchor">41</a></p> + +<p><span class='pagenum'>109</span></p><p>The <i>Epistle</i> 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:</p> + +<div class="blockquot"><p>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.</p></div> + +<p>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 +<i>Epistle</i> 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 <i>Epistle</i>, +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."</p> + + +<p class="tb">This tells us incidentally, that the perpetual motion +device was a subject of considerable interest at this +time.<a name="FNanchor_42" id="FNanchor_42"></a><a href="#Footnote_42" class="fnanchor">42</a> Oddly enough, Peter does not now develop +his idea of the terrella, but proceeds to something +quite new, a device (see fig. <a href="#fig_22">22</a>) 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.</p> + +<div class="figcenter" style="width: 400px;"><a name="fig_22" id="fig_22" /><img src="images/fig_22.jpg" width="400" height="395" alt= +"Magnetic Perpetual Motion Wheel." title="" /> + +<div class="caption">Figure 22.—<span class="smcap">Magnetic Perpetual Motion Wheel</span> +illustrated by Peter Peregrinus; from the edition of +S. P. Thompson (see footnote <a href="#Footnote_40">40</a>).</div></div> + +<p>The work of Peter Peregrinus is cited by Roger +Bacon in his <i>De secretis</i> as well as in the <i>Opus majus</i> +<span class='pagenum'>110</span>and <i>Opus minus</i>. 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 <i>Opus +minus</i>, where he repeats reference to this device, does +he finally reveal that it is to be made to work by +means of the loadstone.</p> + +<p>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 <i>Epistle</i> +(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.</p> + +<p>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.</p> + + +<h3><a name="Page_110a" id="Page_110a">The Magnetic Compass as a Fellow-traveler +from China</a></h3> + +<p>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 <i>ca.</i> 1086.</p> + +<p>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 <i>De naturis rerum</i> and <i>De +utensilibus</i> of Alexander Neckham<a name="FNanchor_43" id="FNanchor_43"></a><a href="#Footnote_43" class="fnanchor">43</a> (<i>ca.</i> 1187) and +a text by Hugues de Berze<a name="FNanchor_44" id="FNanchor_44"></a><a href="#Footnote_44" class="fnanchor">44</a> (after <i>ca.</i> 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 +(<i>ca.</i> 1200) in a poem by Guyot de Provins, and in a +history of Jerusalem by Jacques de Vitry (1215).<a name="FNanchor_45" id="FNanchor_45"></a><a href="#Footnote_45" class="fnanchor">45</a> +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.</p> + +<p>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 <i>ca.</i> 1230,<a name="FNanchor_46" id="FNanchor_46"></a><a href="#Footnote_46" class="fnanchor">46</a> 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 (<i>ca.</i> +1282), the ordinary wet-compass is termed "al-konbas," +another indication that it was foreign to +that language and culture.<a name="FNanchor_47" id="FNanchor_47"></a><a href="#Footnote_47" class="fnanchor">47</a></p> + + +<p><span class='pagenum'>111</span></p> + +<h2>Chronological Chart</h2> + +<hr style="width: 100%; margin-top: 0em; + margin-bottom: 0em;" /> + +<table width="100%" summary="Chronological_Chart" border="0"> + +<tr> +<td class="td100c"><span class="smcap">China</span></td> +</tr> + +<tr> +<td class="td100"><p class="indent">4th C., B.C. Power gearing</p></td> +</tr> + +<tr> +<td class="td100c"><span class="smcap">Classical Europe</span></td> +</tr> + +<tr> +<td class="td100"><p class="indent">3rd C., B.C. Archimedes planetarium</p></td> +</tr> + +<tr> +<td class="td100"><p class="indent">2nd C., B.C. Hipparchus Stereographic Projection</p></td> +</tr> + +<tr> +<td class="td100"><p class="indent">1st C., B.C. Vitruvius hodometer and water clocks</p></td> +</tr> + +<tr> +<td class="td100"><p class="indent">65, B.C. (<i>ca.</i>) Antikythera machine</p></td> +</tr> + +<tr> +<td class="td100"><p class="indent">1st C., A.D. Hero hodometer and water clocks</p></td> +</tr> + +<tr> +<td class="td100"><p class="indent">2nd C., A.D. Salzburg and Vosges anaphoric clocks</p></td> +</tr> + +<tr> +<td class="td100c"><span class="smcap">China</span></td> +</tr> + +<tr> +<td class="td100"><p class="indent">2nd C., A.D. Chang H&ecirc;ng animated globe hodometer</p></td> +</tr> + +<tr> +<td class="td100"><p class="indent"> Continuing tradition of animated astronomical models</p></td> +</tr> + +<tr> +<td class="td100"><p class="indent"> 725 Invention of Chinese escapement by I-Hsing and Liang Ling-tsan</p></td> +</tr> + +<tr> +<td class="td100c"><span class="smcap">Islam</span></td> +</tr> + +<tr> +<td class="td100"><p class="indent"> 807 Harun-al-Rashid</p></td> +</tr> + + +<tr> +<td class="td100"><p class="indent"> 850 (<i>ca.</i>) Earliest extant astrolobes</p></td> +</tr> + +<tr> +<td class="td100"><p class="indent">1000 Geared astrolabe of Buruni</p></td> +</tr> + +<tr> +<td class="td100c"><span class="smcap">Europe</span></td> +</tr> + +<tr> +<td class="td100"><p class="indent">1000 Gerbert astronomical model</p></td> +</tr> + +<tr> +<td class="td100c"><span class="smcap">Islam</span></td> +</tr> + +<tr> +<td class="td100"><p class="indent">1025 Equatorium text</p></td> +</tr> + +<tr> +<td class="td100c"><span class="smcap">China</span></td> +</tr> + +<tr> +<td class="td100"><p class="indent">1074 Shen Kua, clocks and magnetic compass</p></td> +</tr> + +<tr> +<td class="td100"><p class="indent">1080 Su Sung clock built</p></td> +</tr> + +<tr> +<td class="td100"><p class="indent">1101 Su Sung clock destroyed</p></td> +</tr> + +<tr> +<td class="td100c"><span class="smcap">India</span></td> +</tr> + +<tr> +<td class="td100"><p class="indent">1100 (<i>ca.</i>) Sūrya Siddhānta animated astronomical models and perpetual motion</p></td> +</tr> + +<tr> +<td class="td100"><p class="indent">1150 (<i>ca.</i>) Siddhānta Siromaṇi animated models and perpetual motion</p></td> +</tr> + +<tr> +<td class="td100c"><span class="smcap">Islam</span></td> +</tr> + +<tr> +<td class="td100"><p class="indent">1150 Saladin clock</p></td> +</tr> + +<tr> +<td class="td100c"><span class="smcap">Europe</span></td> +</tr> + +<tr> +<td class="td100"><p class="indent">1187 Neckham on compass</p></td> +</tr> + +<tr> +<td class="td100"><p class="indent">1198 Jocelin on water clock</p></td> +</tr> + +<tr> +<td class="td100c"><span class="smcap">Islam</span></td> +</tr> + +<tr> +<td class="td100"><p class="indent">1200 (<i>ca.</i>) Riḍwān water-clocks, perpetual motion and weight drive</p></td> +</tr> + +<tr> +<td class="td100"><p class="indent">1206 al-Jazarī clocks, etc.</p></td> +</tr> + +<tr> +<td class="td100"><p class="indent">1221 Geared astrolabe</p></td> +</tr> + +<tr> +<td class="td100"><p class="indent">1232 Charlemagne clock</p></td> +</tr> + +<tr> +<td class="td100"><p class="indent">1243 al-Konbas (compass)</p></td> +</tr> + +<tr> +<td class="td100c"><span class="smcap">Europe</span></td> +</tr> + +<tr> +<td class="td100"><p class="indent">1245 Villard clocktower, "escapement," perpetual motion</p></td> +</tr> + +<tr> +<td class="td100"><p class="indent">1267 Villers Abbey clock</p></td> +</tr> + +<tr> +<td class="td100"><p class="indent">1269 Peregrinus, compass and perpetual motion</p></td> +</tr> + +<tr> +<td class="td100"><p class="indent">1271 Robertus Anglicus, animated models and "perpetual motion" clock</p></td> +</tr> + +<tr> +<td class="td100c"><span class="smcap">Islam</span></td> +</tr> + +<tr> +<td class="td100"><p class="indent">1272 Alfonsine corpus clock with mercury drum, equatoria</p></td> +</tr> + +<tr> +<td class="td100c"><span class="smcap">Europe</span></td> +</tr> + +<tr> +<td class="td100"><p class="indent">1285 Drover's water clock with wheel and weight drive</p></td> +</tr> + +<tr> +<td class="td100"><p class="indent">1300 (<i>ca.</i>) French geared astrolabe</p></td> +</tr> + +<tr> +<td class="td100"><p class="indent">1320 Richard of Wallingford astronomical clock and equatorium</p></td> +</tr> + +<tr> +<td class="td100"><p class="indent">1364 de Dondi's astronomical clock with mechanical escapement</p></td> +</tr> + +<tr> +<td class="td100"><p class="indent">later 14th C. Tradition of escapement clocks continues and degenerates into simple time-keepers</p></td> +</tr> + +</table> +<hr style="width: 100%; margin-top: 1em;" /> +<p><span class='pagenum'>112</span></p> + + +<p class="tb">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, <i>ca.</i> 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 <i>ca.</i> 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.</p> + +<p>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.</p> + +<h3>FOOTNOTES:</h3> + +<div class="footnote"><p><a name="Footnote_1" id="Footnote_1"></a><a href="#FNanchor_1"><span class="label">1</span></a> 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, <i>A history +of inventions and discoveries</i>, 4th ed., London, 1846, vol. 1, pp. +340 ff. A. P. Usher, <i>A history of mechanical inventions</i>, 2nd ed., +Harvard University Press. 1954, pp. 191 ff., 304 ff.</p></div> + +<div class="footnote"><p><a name="Footnote_2" id="Footnote_2"></a><a href="#FNanchor_2"><span class="label">2</span></a> There is a considerable literature dealing with the later +evolution of perpetual motion devices. The most comprehensive +treatment is H. Dircks, <i>Perpetuum mobile</i>, 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.</p></div> + +<div class="footnote"><p><a name="Footnote_3" id="Footnote_3"></a><a href="#FNanchor_3"><span class="label">3</span></a> For the early history of gearing in the West see C. Matschoss, +<i>Geschichte des Zahnrades</i>, Berlin, 1940. Also F. M. +Feldhaus, <i>Die geschichtliche Entwicklung des Zahnrades in Theorie +und Praxis</i>, Berlin, 1911.</p></div> + +<div class="footnote"><p><a name="Footnote_4" id="Footnote_4"></a><a href="#FNanchor_4"><span class="label">4</span></a> A general account of these important archaeological objects +will be published by J. Needham, <i>Science and civilisation in China</i>, +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," <i>National Peiping Academy Historical Journal</i>, 1937, +vol. 3, p. 1. Liu Hsien-chou, "Chinese inventions in horological +engineering," <i>Ch'ing-Hua University Engineering Journal</i>, +1956, vol. 4, p. 1.</p></div> + +<div class="footnote"><p><a name="Footnote_5" id="Footnote_5"></a><a href="#FNanchor_5"><span class="label">5</span></a> For illustrations of intermeshing worms in Indian cotton +mills, see Matschoss, <i>op. cit.</i> (footnote <a href="#Footnote_3">3</a>), figs. 5, 6, 7, p. 7.</p></div> + +<div class="footnote"><p><a name="Footnote_6" id="Footnote_6"></a><a href="#FNanchor_6"><span class="label">6</span></a> 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."</p></div> + +<div class="footnote"><p><a name="Footnote_7" id="Footnote_7"></a><a href="#FNanchor_7"><span class="label">7</span></a> A summary of the content of the manuscript sources, illustrated +by the original drawings, has been published by H. Alan +Lloyd, <i>Giovanni de Dondi's horological masterpiece, 1364</i>, 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.</p></div> + +<div class="footnote"><p><a name="Footnote_8" id="Footnote_8"></a><a href="#FNanchor_8"><span class="label">8</span></a> See, for example, the chronological tables of the 14th +century and the later mentions of clocks in E. Zinner, <i>Aus der +Fr&uuml;hzeit der R&auml;deruhr</i>, 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. <a href="#fig_20">107</a>). An excellent and fully +illustrated account of monumental astronomical clocks throughout +the world is given by Alfred Ungerer, <i>Les horloges astronomiques</i>, +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, +<i>From the Aratus globe to the Zeiss planetarium</i>, Stuttgart, 1957; +C. A. Crommelin, "Planetaria, a historical survey," <i>Antiquarian +Horology</i>, 1955, vol. 1, pp. 70-75.</p></div> + +<div class="footnote"><p><a name="Footnote_9" id="Footnote_9"></a><a href="#FNanchor_9"><span class="label">9</span></a> Derek J. Price, "Clockwork before the clock," <i>Horological +Journal</i>, 1955, vol. 97, p. 810, and 1956, vol. 98, p. 31.</p></div> + +<div class="footnote"><p><a name="Footnote_10" id="Footnote_10"></a><a href="#FNanchor_10"><span class="label">10</span></a> 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," <i>Nature</i>, +1956, vol. 177, pp. 600-602.</p></div> + +<div class="footnote"><p><a name="Footnote_11" id="Footnote_11"></a><a href="#FNanchor_11"><span class="label">11</span></a> 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.</p></div> + +<div class="footnote"><p><a name="Footnote_12" id="Footnote_12"></a><a href="#FNanchor_12"><span class="label">12</span></a> A. G. Drachmann, "The plane astrolabe and the anaphoric +clock," <i>Centaurus</i>, 1954, vol. 3, pp. 183-189.</p></div> + +<div class="footnote"><p><a name="Footnote_13" id="Footnote_13"></a><a href="#FNanchor_13"><span class="label">13</span></a> A fuller description of the anaphoric clock and cognate +water-clocks is given by A. G. Drachmann, "Ktesibios, Philon +and Heron," <i>Acta Historica Scientiarum Naturalium et Medicinalium</i>, +Copenhagen, 1948, vol. 4.</p></div> + +<div class="footnote"><p><a name="Footnote_14" id="Footnote_14"></a><a href="#FNanchor_14"><span class="label">14</span></a> First published by O. Benndorf, E. Weiss, and A. Rehm, +<i>Jahreshefte des &ouml;sterreichischen arch&auml;ologischen Institut in Wien</i>, +1903, vol. 6, pp. 32-49. I have given further details of its +construction in <i>A history of technology</i>, ed. Singer, Holmyard, +and Hall, 1957, vol. 3, pp. 604-605.</p></div> + +<div class="footnote"><p><a name="Footnote_15" id="Footnote_15"></a><a href="#FNanchor_15"><span class="label">15</span></a> L. Maxe-Werly, <i>M&eacute;moires de la Soci&eacute;t&eacute; Nationale des Antiquaires +de France</i>, 1887, vol. 48, pp. 170-178.</p></div> + +<div class="footnote"><p><a name="Footnote_16" id="Footnote_16"></a><a href="#FNanchor_16"><span class="label">16</span></a> The first definitive account of the Antikythera machine +was given by Perikles Rediadis in J. Svoronos, <i>Das Athener +Nationalmuseum</i>, 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, <i>Praktika tes Akademias +Athenon</i>, 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.</p></div> + +<div class="footnote"><p><a name="Footnote_17" id="Footnote_17"></a><a href="#FNanchor_17"><span class="label">17</span></a> H. Diels &Uuml;ber die von Prokop beschriebene Kunstuhr von +Gaza, <i>Abhandlungen, Akademie der Wissenschaften</i>, Berlin, Philos.-Hist. +Klasse, 1917, No. 7.</p></div> + +<div class="footnote"><p><a name="Footnote_18" id="Footnote_18"></a><a href="#FNanchor_18"><span class="label">18</span></a> L. A. Mayer, <i>Islamic astrolabists and their works</i>, Geneva, +1956, p. 62.</p></div> + +<div class="footnote"><p><a name="Footnote_19" id="Footnote_19"></a><a href="#FNanchor_19"><span class="label">19</span></a> The translation which follows is quoted from J. Beckmann, +<i>op. cit.</i> (footnote <a href="#Footnote_1">1</a>), p. 349.</p></div> + +<div class="footnote"><p><a name="Footnote_20" id="Footnote_20"></a><a href="#FNanchor_20"><span class="label">20</span></a> E. Wiedemann, "Ein Instrument das die Bewegung von +Sonne und Mond darstellt, nach al Biruni," <i>Der Islam</i>, 1913, +vol. 4, p. 5.</p></div> + +<div class="footnote"><p><a name="Footnote_21" id="Footnote_21"></a><a href="#FNanchor_21"><span class="label">21</span></a> 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, <i>Astrolabes of the world</i>, Oxford, 1932.</p></div> + +<div class="footnote"><p><a name="Footnote_22" id="Footnote_22"></a><a href="#FNanchor_22"><span class="label">22</span></a> Abulcacim Abnacahm, <i>Libros del saber</i>, 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," <i>Bibliotheca Mathematica</i>, +1905, pp. 129-189. A more complete discussion of the +historical evolution of the equatorium is given in Derek J. Price, +<i>The equatorie of the planetis</i>, Cambridge (Eng.), 1955, pp. 119-133.</p></div> + +<div class="footnote"><p><a name="Footnote_23" id="Footnote_23"></a><a href="#FNanchor_23"><span class="label">23</span></a> E. Wiedemann, and F. Hauser, "Uber die Uhren im +Bereich d. islamischen Kultur," <i>Nova Acta; Abhandlungen der +k&ouml;nigliche Leopoldinisch-Carolinische Deutsche Akademie der Naturforscher +zu Halle</i>, 1915, vol. 100, no. 5.</p></div> + +<div class="footnote"><p><a name="Footnote_24" id="Footnote_24"></a><a href="#FNanchor_24"><span class="label">24</span></a> E. Wiedemann, and F. Hauser, <i>Die Uhr des Archimedes und +zwei andere Vorrichtungen</i>, Halle, 1918.</p></div> + +<div class="footnote"><p><a name="Footnote_25" id="Footnote_25"></a><a href="#FNanchor_25"><span class="label">25</span></a> 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.</p></div> + +<div class="footnote"><p><a name="Footnote_26" id="Footnote_26"></a><a href="#FNanchor_26"><span class="label">26</span></a> H. Schmeller, Beitr&auml;ge zur Geschichte der Technik in der +Antike und bei den Arabern, Erlangen, 1922 (<i>Abhandlungen zur +Geschichte der Naturwissenschaften und der Medizin</i> no. 6).</p></div> + +<div class="footnote"><p><a name="Footnote_27" id="Footnote_27"></a><a href="#FNanchor_27"><span class="label">27</span></a> Once more I am indebted to Professor Loren MacKinney +and Miss Harriet Lattin (see footnote <a href="#Footnote_11">11</a>) for making their +collections on Gerbert available to me.</p></div> + +<div class="footnote"><p><a name="Footnote_28" id="Footnote_28"></a><a href="#FNanchor_28"><span class="label">28</span></a> Item 198 in Gunther, <i>op. cit.</i> (footnote <a href="#Footnote_21">21</a>). I am grateful to +the authorities of that museum for permission to reproduce +photographs of this instrument.</p></div> + +<div class="footnote"><p><a name="Footnote_29" id="Footnote_29"></a><a href="#FNanchor_29"><span class="label">29</span></a> Sotheby and Co., London, sale of March 14, 1957, lot 154. +The outer rim of the rete has 120 teeth.</p></div> + +<div class="footnote"><p><a name="Footnote_30" id="Footnote_30"></a><a href="#FNanchor_30"><span class="label">30</span></a> The Latin text of the treatise on the Albion, has been +transcribed by Rev. H. Salter and published in R. T. Gunther, +<i>Early science in Oxford</i>, Oxford, 1923, vol. 2, pp. 349-370. An +analysis of its design is given in Price, <i>op. cit.</i> (footnote <a href="#Footnote_22">22</a>), pp. +127-130.</p></div> + +<div class="footnote"><p><a name="Footnote_31" id="Footnote_31"></a><a href="#FNanchor_31"><span class="label">31</span></a> Such evidence as there is for the existence and form of the +clock is collected by Gunther, <i>op. cit.</i> (footnote <a href="#Footnote_30">30</a>), p. 49.</p></div> + +<div class="footnote"><p><a name="Footnote_32" id="Footnote_32"></a><a href="#FNanchor_32"><span class="label">32</span></a> I have discussed this new manuscript source in "Two +medieval texts on astronomical clocks," <i>Antiquarian Horology</i>, +1956, vol. 1, no. 10, p. 156. The manuscript in question is +ms. 230/116, Gonville and Caius College, Cambridge, folios +11<sup>v</sup>-14<sup>v</sup> = pp. 31-36.</p></div> + +<div class="footnote"><p><a name="Footnote_33" id="Footnote_33"></a><a href="#FNanchor_33"><span class="label">33</span></a> <i>The Chronicle of Jocelin of Brakelond</i> ..., H. E. Butler (ed.), +London, 1949, p. 106.</p></div> + +<div class="footnote"><p><a name="Footnote_34" id="Footnote_34"></a><a href="#FNanchor_34"><span class="label">34</span></a> C. B. Drover, "A medieval monastic water-clock," <i>Antiquarian +Horology</i>, 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.</p></div> + +<div class="footnote"><p><a name="Footnote_35" id="Footnote_35"></a><a href="#FNanchor_35"><span class="label">35</span></a> <i>Annales de la Soci&eacute;t&eacute; Royale d'Arch&eacute;ologie de Bruxelles</i>, 1896, +vol. 1/8, pp. 203-215, 404-451. The translation here is cited +from Drover, <i>op. cit.</i>, (footnote <a href="#Footnote_34">34</a>), p. 56.</p></div> + +<div class="footnote"><p><a name="Footnote_36" id="Footnote_36"></a><a href="#FNanchor_36"><span class="label">36</span></a> L. Thorndike, <i>The sphere of Sacrobosco and its commentators</i>, +Chicago, 1949, pp. 180, 230.</p></div> + +<div class="footnote"><p><a name="Footnote_37" id="Footnote_37"></a><a href="#FNanchor_37"><span class="label">37</span></a> 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, <i>The evolution of clockwork</i>, London, +1931, pp. 11-15.</p></div> + +<div class="footnote"><p><a name="Footnote_38" id="Footnote_38"></a><a href="#FNanchor_38"><span class="label">38</span></a> M. Jules Quicherat, <i>Revue Arch&egrave;ologique</i>, 1849, vol. 6.</p></div> + +<div class="footnote"><p><a name="Footnote_39" id="Footnote_39"></a><a href="#FNanchor_39"><span class="label">39</span></a> M. C. Fr&eacute;mont. <i>Origine de l'horloge &agrave; poids</i>, Paris, 1915.</p></div> + +<div class="footnote"><p><a name="Footnote_40" id="Footnote_40"></a><a href="#FNanchor_40"><span class="label">40</span></a> For this, I have used and quoted from the very beautiful +edition in English, prepared by Silvanus P. Thompson, London, +Chiswick Press, 1902.</p></div> + +<div class="footnote"><p><a name="Footnote_41" id="Footnote_41"></a><a href="#FNanchor_41"><span class="label">41</span></a> See E. G. R. Taylor, "The South-pointing needle," +<i>Imago Mundi</i>, Leiden, 1951, vol. 8, pp. 1-7 (especially pp. 1, 2).</p></div> + +<div class="footnote"><p><a name="Footnote_42" id="Footnote_42"></a><a href="#FNanchor_42"><span class="label">42</span></a> 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.</p></div> + +<div class="footnote"><p><a name="Footnote_43" id="Footnote_43"></a><a href="#FNanchor_43"><span class="label">43</span></a> W. E. May, "Alexander Neckham and the pivoted compass +needle," <i>Journal of the Institute of Navigation</i>, 1955, vol. 8, +no. 3, pp. 283-284.</p></div> + +<div class="footnote"><p><a name="Footnote_44" id="Footnote_44"></a><a href="#FNanchor_44"><span class="label">44</span></a> W. E. May, "Hugues de Berze and the mariner's compass," +<i>The Mariner's Mirror</i>, 1953, vol. 39, no. 2, pp. 103-106.</p></div> + +<div class="footnote"><p><a name="Footnote_45" id="Footnote_45"></a><a href="#FNanchor_45"><span class="label">45</span></a> H. Balmer, <i>Beitr&auml;ge zur Geschichte der Erkenntnis des Erdmagnetismus</i>, +Aarau, 1956, p. 52.</p></div> + +<div class="footnote"><p><a name="Footnote_46" id="Footnote_46"></a><a href="#FNanchor_46"><span class="label">46</span></a> The collection is the <i>Gami 'al Hikajat</i>; the relevant passage +being given in German translation in Balmer. <i>op. cit.</i> (footnote +<a href="#Footnote_45">45</a>), p. 54.</p></div> + +<div class="footnote"><p><a name="Footnote_47" id="Footnote_47"></a><a href="#FNanchor_47"><span class="label">47</span></a> Balmer, op. <i>cit.</i> (footnote <a href="#Footnote_45">45</a>), p. 53.</p></div> + + +<h4>U.S. GOVERNMENT PRINTING OFFICE: 1959</h4> + +<div>*** END OF THE PROJECT GUTENBERG EBOOK 30001 ***</div> +</body> +</html> |