and Ofms minus. In iho first and earliest of these 

 occurs a description, taiccn from Ptolemy, of the 

 construction of llie (observing) annillary S]3heri'. He 

 says that this cannot be made to move naturally by 

 any mathematical device, but "a faithful and mag- 

 nificent 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 po.ssibility 

 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, docs 

 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 Rolierlus 

 Anglicus, already mentioned as an indication of 

 preoccupation with diiunally 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 cjuestion 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 compa.ss 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 load- 

 stone and some of its properties. Then, parallel to 

 the development of protoclocks in China throughout 

 the middle ages, we have the evidence analyzed by 

 Necdham, showing the use of the magnet as a clivina- 

 tory device and of the (nonmagnetic) south-jjointing 

 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 (lO.^O-lO'JS) who 

 also appears in connection with the clock of Su Sung, 

 and who wrote about the mechanized annillary 

 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, pro- 

 vides 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 aw-ay. We know now that 

 tlie famous passages in the Dc naluris rerum and De 

 utensil ibiis of Alexander Neckham *^ {ca. 1187) and 

 a text by Hugues de Berze ''^ (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).^^ 

 It is of the greatest interest that, once more, all the 

 evidence seems to be concentrated in France (Neck- 

 ham 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-'.'\wfi ca. IZ.'^O,^" the instrument used by the cap- 

 tain 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 



'^ VV. E. May, "AlcNandcr Xcckham and the pivoird com- 

 pass needle," Journal of the Institute of Navigation, 1955, vol. 8, 

 no. 3, pp. 283-284. 



** W. E. May, "Hugues dc Berze and the mariner's com- 

 pass," The Mariner'' s Mirror, 1953, vol. 39, no. 2, pp. 103-106. 



'^ H. Balmcr, Beitrage zur Geschichte der Erkenntnis des Erdmag- 

 netismus, Aarau, 1956, p. 52. 



"> The collection i^ the Garni 'a! Hikajat; the relevant passage 

 beinp; given in German translation in Balmcr, op. cit. (foot- 

 note 45), p. 54. 



110 



BULLETIN 218: CONTRIBUTIONS FROM THE MUSEUM OF HISTORY AND TECHNOLOGY 



