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 astrolobes |
| 1000 Geared astrolabe of Buruni |
| 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.