suggests the use of bells because of its open structure, suitable for
letting out the sound. Moreover, he suggests that the delicacy of the
line indicates that it was not really a full-size steeple but rather a
small towerlike structure standing only a few feet high within the
church. There is, alas, nothing to tell us about the clock it was
intended to house; most probably it was a water clock similar to that of
the illustrated Bible of _ca._ 1285.
The drawing of the rope, wheel and axles, for turning an angel to point
towards the sun can have a simple explanation or a more complicated one.
If taken at its face value the wheel on its horizontal axis acts as a
windlass connected by the counterpoised rope to the vertical shaft which
it turns, thereby moving (by hand) the figure of an angel (not shown)
fixed to the top of this latter shaft. Such an explanation was in fact
suggested by M. Quicherat,[38] who first called attention to the Villard
album and pointed out that a leaden angel existed in Chartres before the
fire there in 1836. It is a view also supported from another drawing in
the album which describes an eagle whose head is made to turn towards
the deacon when he reads the Gospel. Slight pressure on the tail of the
bird causes a similar rope mechanism to operate.
A quite different interpretation has been suggested by Frémont;[39] he
believes that the wheel may have acted as a fly-wheel and the ropes and
counterpoises, turning first one way then the other acted as a sort of
mechanical escapement. Such an arrangement is however mechanically
impossible without some complicated free-wheeling device between the
drive and the escapement, and its only effect would be to oscillate the
angel rapidly rather than turn it steadily. I believe that Frémont,
over-anxious to provide a protoescapement, has done too much violence to
the facts and turned away without good reason from the more simple and
reasonable explanation. It is nevertheless still possible to adopt this
simple interpretation and yet to have the system as part of a clock. If
the left-hand counterpoise, conveniently raised higher than that on the
right, is considered as a float fitting into a clepsydra jar, instead of
as a simple weight, one would have a very suitable automatic system for
turning the angel. On this explanation, the purpose of the wheel would
be merely to provide the manual adjustment necessary to set the angel
from time to time, compensating for irremediable inaccuracies of the
clepsydra.
[Illustration: Figure 21.--VILLARD'S PERPETUAL MOTION WHEEL, from Lassus
(see footnote 37).]
Having discussed the Villard drawings which are already cited in
horological literature, we must draw attention to the fact that this
medieval architect also gives an illustration of a perpetual motion
wheel. In this case (fig. 21) it is of the type having weights at the
end of swinging arms, a type that occurs very frequently at later dates
in Europe and is also given in the Islamic texts. We cannot, in this
case, suggest that drawings of clocks and of perpetual motion devices
occur together by more than a coincidence, for Villard seems to have
been interested in most sorts of mechanical device. But even this type
of coincidence becomes somewhat striking when repeated often enough. It
seems that each early mention of "self-moving wheels" occurs in
connection with some sort of clock or mechanized astronomical device.
Having now completed a survey of the traditions of astronomical models,
we have seen that many types of device embodying features later found in
mechanical clocks evolved through various cultures and flowed into
Europe, coming together in a burst of multifarious activity during the
second half of the 13th century, notably in the region of France. We
must now attempt to fill the residual gap, and in so doing examine the
importance of perpetual motion devices, mechanical and magnetic, in the
crucial transition from protoclock to mechanical-escapement clock.
Perpetual Motion and the Clock before de Dondi
We have already noted, more or less briefly, several instances of the
use of wheels "moving by themselves" or the use of a fluid for purposes
other than as a motive power. Chronologically arranged, these are the
Indian devices of _ca._ 1150 or a little earlier, as those of Riḍwān
_ca._ 1200, that of the Alfonsine mercury clock, _ca._ 1272, and the
French Bible illumination of _ca._ 1285. This strongly suggests a steady
transmission from East to West, and on the basis of it, we now
tentatively propose an additional step, a transmission from China to
India and perhaps further West, _ca._ 1100, and possibly reinforced by
further transmissions at later dates.
One need only assume the existence of vague traveler's tales about the
existence of the 11th-century Chinese clocks with their astronomical
models and jackwork and with their great wheel, apparently moving by
itself but using water having no external inlet or outlet. Such a
stimulus, acting as it did on a later occasion when Galileo received
word of the invention of the telescope in the Low Countries, might
easily lead to the re-invention of just such perpetual-motion wheels as
we have already noted. In many ways, once the idea has been suggested it
is natural to associate such a perpetual motion with the incessant
diurnal rotation of the heavens. Without some such stimulus however it
is difficult to explain why this association did not occur earlier, and
why, once it comes there seems to be such a chronological procession
from culture to culture.
We now turn to what is undoubtedly the most curious part of this story,
in which automatically moving astronomical models and perpetual motion
wheels are linked with the earliest texts on magnetism and the magnetic
compass, another subject with a singularly troubled historical origin.
The key text in this is the famous _Epistle on the magnet_, written by
Peter Peregrinus, a Picard, in an army camp at the Siege of Lucera and
dated August 8, 1269.[40] In spite of the precise dating it is certain
that the work was done long before, for it is quoted unmistakably by
Roger Bacon in at least three places, one of which must have been
written before _ca._ 1250.[41]
The _Epistle_ contains two parts; in the first there is a general
account of magnetism and the properties of the loadstone, closing with a
discussion "of the inquiry whence the magnet receives the natural virtue
which it has." Peter attributed this virtue to a sympathy with the
heavens, proposing to prove his point by the construction of a
"terrella," a uniform sphere of loadstone which is to be carefully
balanced and mounted in the manner of an armillary sphere, with its axis
directed along the polar axis of the diurnal rotation. He then
continues:
Now if the stone then move according to the motion of the
heavens, rejoice that you have arrived at a secret marvel.
But if not, let it be ascribed rather to your own want of
skill than to a defect of Nature. But in this position, or
mode of placing, I deem the virtues of this stone to be
properly conserved, and I believe that in other positions
or parts of the sky its virtue is dulled, rather than
preserved. By means of this instrument at all events you
will be relieved from every kind of clock (horologium),
for by it you will be able to know the Ascendant at
whatever hour you will, and all other dispositions of the
heavens which Astrologers seek after.
It should be noted that the device is to be mounted like an astronomical
instrument and used like one, rather than as a time teller, or as a
simple demonstration of magnetism. In the second part of the _Epistle_
Peter turns to practical instruments, describing for the first time, the
construction of a magnetic compass consisting of a loadstone or iron
needle pivoted with a casing marked with a scale of degrees. The third
chapter of this section, concluding the _Epistle_, then continues with
the description of a perpetual motion wheel, "elaboured with marvellous
ingenuity, in the pursuit of which invention I have seen many people
wandering about, and wearied with manifold toil. For they did not
observe that they could arrive at the mastery of this by means of the
virtue, or power of this stone."
This tells us incidentally, that the perpetual motion device was a
subject of considerable interest at this time.[42] Oddly enough, Peter
does not now develop his idea of the terrella, but proceeds to something
quite new, a device (see fig. 22) in which a bar-magnet loadstone is to
be set towards the end of a pivoted radial arm with a circle fitted on
the inside with iron "gear teeth," the teeth being there not to mesh
with others but to draw the magnet from one to the next, a little bead
providing a counterweight to help the inertia of rotation carry the
magnet from one point of attraction to the next. It is by no means the
sort of device that one would naturally evolve as a means of making
magnetism work perpetually, and I suggest that the toothed wheel is
another instance of some vague idea of protoclocks, perhaps that of Su
Sung, being transmitted from the East.
[Illustration: Figure 22.--MAGNETIC PERPETUAL MOTION WHEEL illustrated
by Peter Peregrinus; from the edition of S. P. Thompson (see footnote
40).]
The work of Peter Peregrinus is cited by Roger Bacon in his _De
secretis_ as well as in the _Opus majus_ and _Opus minus_. In the first
and earliest of these occurs a description, taken from Ptolemy, of the
construction of the (observing) armillary sphere. He says that this
cannot be made to move naturally by any mathematical device, but "a
faithful and magnificent experimentor is straining to make one out of
such material, and by such a device, that it will revolve naturally with
the diurnal heavenly rotation." He continues with the statement that
this possibility is also suggested by the fact that the motions of
comets, of tides, and of certain planets also follow that of the Sun and
of the heavens. Only in the _Opus minus_, where he repeats reference to
this device, does he finally reveal that it is to be made to work by
means of the loadstone.
The form of Bacon's reference to Peregrinus is strongly reminiscent of
the statement by Robertus Anglicus, already mentioned as an indication
of preoccupation with diurnally rotating wheels, at a date (1271)
remarkably close to that of the _Epistle_ (1269)--so much so that it
could well be thought that the friend to which Peter was writing was
either Robert himself or somebody associated with him, perhaps at the
University of Paris--a natural place to which the itinerant Peter might
communicate his findings.
The fundamental question here, of course, is whether the idea of an
automatic astronomical device was transmitted from Arabic, Indian, or
Chinese sources, or whether it arose quite independently in this case as
a natural concomitant of identifying the poles of the magnet with the
poles of the heavens. We shall now attempt to show that the history of
the magnetic compass might provide a quite independent argument in
favour of the hypothesis that there was a 'stimulus' transmission.
The Magnetic Compass as a Fellow-traveler from China
The elusive history of the magnetic compass has many points in common
with that of the mechanical clock. Just as we have astronomical models
from the earliest times, so we find knowledge of the loadstone and some
of its properties. Then, parallel to the development of protoclocks in
China throughout the middle ages, we have the evidence analyzed by
Needham, showing the use of the magnet as a divinatory device and of the
(nonmagnetic) south-pointing chariot, which has been confusedly allied
to the story. Curiously, and perhaps significantly the Chinese history
comes to a head at just the same time for compasses and clocks, and a
prime authority for the Chinese compass is Shen Kua (1030-1093) who also
appears in connection with the clock of Su Sung, and who wrote about the
mechanized armillary spheres and other models _ca._ 1086.
Another similarity occurs in connection with the history of the compass
in medieval Europe. The treatise of Peter Peregrinus, already discussed,
provides the first complete account of the magnetic compass with a
pivoted needle and a circular scale, and this, as we have seen, may be
connected with protoclocks and perpetual-motion devices. There are
several earlier references, however, to the use of the directive
properties of loadstone, mainly for use in navigation, but these
earliest texts have a long history of erroneous interpretation which is
only recently being cleared away. We know now that the famous passages
in the _De naturis rerum_ and _De utensilibus_ of Alexander Neckham[43]
(_ca._ 1187) and a text by Hugues de Berze[44] (after _ca._ 1204) refer
to nothing more than a floating magnet without pivot or scale, but using
a pointer at right angles to the magnet, so that it pointed to the east,
rather than the north or south. A similar method is described (_ca._
1200) in a poem by Guyot de Provins, and in a history of Jerusalem by
Jacques de Vitry (1215).[45] It is of the greatest interest that, once
more, all the evidence seems to be concentrated in France (Neckham was
teaching in Paris) though at an earlier period than that for the
protoclocks.
The date might suggest the time of the first great wave of transmissal
of learning from Islam, but it is clear that in this instance, peculiar
for that reason, that Islam learned of the magnetic compass only after
it was already known in the West. In the earliest Persian record, some
anecdotes compiled by al-'Awfiī _ca._ 1230,[46] the instrument used
by the captain during a storm at sea has the form of a piece of hollow
iron, shaped like a fish and made to float on the water after
magnetization by rubbing with a loadstone; the fishlike form is very
significant, for this is distinctly Chinese practice. In a second Muslim
reference, that of Bailak al-Qabājaqī (_ca._ 1282), the ordinary
wet-compass is termed "al-konbas," another indication that it was
foreign to that language and culture.[47]
Chronological Chart
------------------------------------------------------------------------
CHINA
4th C., B.C. Power gearing
CLASSICAL EUROPE
3rd C., B.C. Archimedes planetarium
2nd C., B.C. Hipparchus Stereographic Projection
1st C., B.C. Vitruvius hodometer and water clocks
65, B.C. (_ca._) Antikythera machine
1st C., A.D. Hero hodometer and water clocks
2nd C., A.D. Salzburg and Vosges anaphoric clocks
CHINA
2nd C., A.D. Chang Hêng animated globe hodometer
Continuing tradition of animated astronomical models
725 Invention of Chinese escapement by I-Hsing and Liang Ling-tsan
ISLAM
807 Harun-al-Rashid
850 (_ca._) Earliest extant astrolabes
1000 Geared astrolabe of al-Biruni
EUROPE
1000 Gerbert astronomical model
ISLAM
1025 Equatorium text
CHINA
1074 Shen Kua, clocks and magnetic compass
1080 Su Sung clock built
1101 Su Sung clock destroyed
INDIA
1100 (_ca._) Sūrya Siddhānta animated astronomical models
and perpetual motion
1150 (_ca._) Siddhānta Siromaṇi animated models and perpetual
motion
ISLAM
1150 Saladin clock
EUROPE
1187 Neckham on compass
1198 Jocelin on water clock
ISLAM
1200 (_ca._) Riḍwān water-clocks, perpetual motion
and weight drive
1206 al-Jazarī clocks, etc.
1221 Geared astrolabe
1232 Charlemagne clock
1243 al-Konbas (compass)
EUROPE
1245 Villard clocktower, "escapement," perpetual motion
1267 Villers Abbey clock
1269 Peregrinus, compass and perpetual motion
1271 Robertus Anglicus, animated models and "perpetual motion" clock
ISLAM
1272 Alfonsine corpus clock with mercury drum, equatoria
EUROPE
1285 Drover's water clock with wheel and weight drive
1300 (_ca._) French geared astrolabe
1320 Richard of Wallingford astronomical clock and equatorium
1364 de Dondi's astronomical clock with mechanical escapement
later 14th C. Tradition of escapement clocks continues
and degenerates into simple time-keepers
------------------------------------------------------------------------
There is therefore reasonable grounds for supporting the medieval
European tradition that the magnetic compass had first come from China,
though one cannot well admit that the first news of it was brought, as
the legend states, by Marco Polo, when he returned home in 1260. There
might well have been another wave of interest, giving the impetus to
Peter Peregrinus at this time, but an earlier transmission, perhaps
along the silk road or by travelers in crusades, must be postulated to
account for the evidence in Europe, _ca._ 1200. The earlier influx does
not play any great part in our main story; it arrived in Europe before
the transmission of astronomy from Islam had got under way sufficiently
to make protoclocks a subject of interest. For a second transmission, we
have already seen how the relevant texts seem to cluster, in France
_ca._ 1270, around a complex in which the protoclocks seem combined with
the ideas of perpetual motion wheels and with new information about the
magnetic compass.
The point of this paper is that such a complex exists, cutting across
the histories of the clock, the various types of astronomical machines,
and the magnetic compass, and including the origin of "self-moving
wheels." It seems to trace a path extending from China, through India
and through Eastern and Western Islam, ending in Europe in the Middle
Ages. This path is not a simple one, for the various elements make their
appearances in different combinations from place to place, sometimes one
may be dominant, sometimes another may be absent. Only by treating it as
a whole has it been possible to produce the threads of continuity which
will, I hope, make further research possible, circumventing the blind
alleys found in the past and leading eventually to a complete
understanding of the first complicated scientific machines.
FOOTNOTES:
[1] This traditional view is expressed by almost every history
of horology. An ultimate source for many of these has been the
following two classic treatments: J. Beckmann, _A history of
inventions and discoveries_, 4th ed., London, 1846, vol. 1, pp.
340 ff. A. P. Usher, _A history of mechanical inventions_, 2nd
ed., Harvard University Press. 1954, pp. 191 ff., 304 ff.
[2] There is a considerable literature dealing with the later
evolution of perpetual motion devices. The most comprehensive
treatment is H. Dircks, _Perpetuum mobile_, London, 1861; 2nd
ser., London, 1870. So far as I know there has not previously
been much discussion of the history of such devices before the
renaissance.
[3] For the early history of gearing in the West see C.
Matschoss, _Geschichte des Zahnrades_, Berlin, 1940. Also F. M.
Feldhaus, _Die geschichtliche Entwicklung des Zahnrades in
Theorie und Praxis_, Berlin, 1911.
[4] A general account of these important archaeological objects
will be published by J. Needham, _Science and civilisation in
China_, Cambridge, 1959(?), vol. 4. The original publications
(in Chinese) are as follows: Wang Chen-to, "Investigations and
reproduction in model form of the south-pointing carriage and
hodometer," _National Peiping Academy Historical Journal_,
1937, vol. 3, p. 1. Liu Hsien-chou, "Chinese inventions in
horological engineering," _Ch'ing-Hua University Engineering
Journal_, 1956, vol. 4, p. 1.
[5] For illustrations of intermeshing worms in Indian cotton
mills, see Matschoss, _op. cit._ (footnote 3), figs. 5, 6, 7,
p. 7.
[6] It is interesting to note that the Chinese hodometer was
contemporary with that of Hero and Vitruvius and very similar
in design. There is no evidence whatsoever upon which to decide
whether there may have been a specific transmission of this
invention or even a "stimulus diffusion."
[7] A summary of the content of the manuscript sources,
illustrated by the original drawings, has been published by H.
Alan Lloyd, _Giovanni de Dondi's horological masterpiece,
1364_, without date or imprint (?Lausanne, 1955), 23 pp. It
should be remarked that de Dondi declines to describe the
workings of his crown and foliot escapement (though it is well
illustrated) saying that this is of the "common" variety and if
the reader does not understand such simple things he need not
hope to comprehend the complexities of this mighty clock. But
this may be bravado to quite a large degree.
[8] See, for example, the chronological tables of the 14th
century and the later mentions of clocks in E. Zinner, _Aus der
Frühzeit der Räderuhr_, Munich, 1954, p. 29 ff. Unfortunately
this very complete treatment tends to confuse the factual and
legendary sources prior to the clock of de Dondi; it also
accepts the very doubtful evidence of the "escapement" drawn by
Villard of Honnecourt (see p. 107). An excellent and fully
illustrated account of monumental astronomical clocks
throughout the world is given by Alfred Ungerer, _Les horloges
astronomiques_, Strasbourg, 1931, 514 pp. Available accounts of
the development of the planetarium since the middle ages are
very brief and especially weak on the early history: Helmut
Werner, _From the Aratus globe to the Zeiss planetarium_,
Stuttgart, 1957; C. A. Crommelin, "Planetaria, a historical
survey," _Antiquarian Horology_, 1955, vol. 1, pp. 70-75.
[9] Derek J. Price, "Clockwork before the clock," _Horological
Journal_, 1955, vol. 97, p. 810, and 1956, vol. 98, p. 31.
[10] For the use of this material I am indebted to my
co-authors. I must also acknowledge thanks to the Cambridge
University Press, which in the near future will be publishing
our monograph, "Heavenly Clockwork." Some of the findings of
this paper are included in shorter form as background material
for that monograph. A brief account of the discovery of this
material has been published by J. Needham, Wang Ling, and Derek
J. Price, "Chinese astronomical clockwork," _Nature_, 1956,
vol. 177, pp. 600-602.
[11] For these translations from classical authors I am
indebted to Professor Loren MacKinney and Miss Harriet Lattin,
who had collected them for a history, now abandoned, of
planetariums. I am grateful for the opportunity of giving them
here the mention they deserve.
[12] A. G. Drachmann, "The plane astrolabe and the anaphoric
clock," _Centaurus_, 1954, vol. 3, pp. 183-189.
[13] A fuller description of the anaphoric clock and cognate
water-clocks is given by A. G. Drachmann, "Ktesibios, Philon
and Heron," _Acta Historica Scientiarum Naturalium et
Medicinalium_, Copenhagen, 1948, vol. 4.
[14] First published by O. Benndorf, E. Weiss, and A. Rehm,
_Jahreshefte des österreichischen archäologischen Institut in
Wien_, 1903, vol. 6, pp. 32-49. I have given further details of
its construction in _A history of technology_, ed. Singer,
Holmyard, and Hall, 1957, vol. 3, pp. 604-605.
[15] L. Maxe-Werly, _Mémoires de la Société Nationale des
Antiquaires de France_, 1887, vol. 48, pp. 170-178.
[16] The first definitive account of the Antikythera machine
was given by Perikles Rediadis in J. Svoronos, _Das Athener
Nationalmuseum_, Athens, 1908, Textband I, pp. 43-51. Since
then, other photographs (mostly very poor) have appeared, and
an attempt at a reconstruction has been made by Rear Admiral
Jean Theophanidis, _Praktika tes Akademias Athenon_, Athens,
1934, vol. 9, pp. 140-149 (in French). I am deeply grateful to
the Director of the Athens National Museum, M. Karouzos, for
providing me with an excellent new set of photos, from which
figures 6-8 are now taken.
[17] H. Diels Über die von Prokop beschriebene Kunstuhr von
Gaza, _Abhandlungen, Akademie der Wissenschaften_, Berlin,
Philos.-Hist. Klasse, 1917, No. 7.
[18] L. A. Mayer, _Islamic astrolabists and their works_,
Geneva, 1956, p. 62.
[19] The translation which follows is quoted from J. Beckmann,
_op. cit._ (footnote 1), p. 349.
[20] E. Wiedemann, "Ein Instrument das die Bewegung von Sonne
und Mond darstellt, nach al Biruni," _Der Islam_, 1913, vol. 4,
p. 5.