[34] C. B. Drover, "A medieval monastic water-clock," Antiquarian Horology, 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.
[35] Annales de la Société Royale d'Archéologie de Bruxelles, 1896, vol. 1/8, pp. 203-215, 404-451. The translation here is cited from Drover, op. cit., (footnote [34]), p. 56.
[36] L. Thorndike, The sphere of Sacrobosco and its commentators, Chicago, 1949, pp. 180, 230.
[37] 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, The evolution of clockwork, London, 1931, pp. 11-15.
[38] M. Jules Quicherat, Revue Archèologique, 1849, vol. 6.
[39] M. C. Frémont. Origine de l'horloge à poids, Paris, 1915.
[40] For this, I have used and quoted from the very beautiful edition in English, prepared by Silvanus P. Thompson, London, Chiswick Press, 1902.
[41] See E. G. R. Taylor, "The South-pointing needle," Imago Mundi, Leiden, 1951, vol. 8, pp. 1-7 (especially pp. 1, 2).
[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.