[42] I have wondered whether the medieval interest in perpetual motion could be connected with the use of the "Wheel of Fortune" in churches as a substitute for bell-ringing on Good Friday. Unfortunately I can find no evidence for or against the conjecture. [43] W. E. May, "Alexander Neckham and the pivoted compass needle," _Journal of the Institute of Navigation_, 1955, vol. 8, no. 3, pp. 283-284. [44] W. E. May, "Hugues de Berze and the mariner's compass," _The Mariner's Mirror_, 1953, vol. 39, no. 2, pp. 103-106. [45] H. Balmer, _Beiträge zur Geschichte der Erkenntnis des Erdmagnetismus_, Aarau, 1956, p. 52. [46] The collection is the _Gami 'al Hikajat_; the relevant passage being given in German translation in Balmer. _op. cit._ (footnote 45), p. 54. [47] Balmer, op. _cit._ (footnote 45), p. 53. U.S. GOVERNMENT PRINTING OFFICE: 1959 End of the Project Gutenberg EBook of On the Origin of Clockwork, Perpetual Motion Devices, and the Compass, by Derek J. de Solla Price