the permission to reproduce photographs of this instrument. It
is item 5 in R. T. Gunther, _Astrolabes of the world_, Oxford,
1932.
[22] Abulcacim Abnacahm, _Libros del saber_, edition by Rico y
Sinobas, Madrid, 1866, vol. 3, pp. 241-271. The design of the
instrument has been very fully discussed by A. Wegener, "Die
astronomischen Werke Alfons X," _Bibliotheca Mathematica_,
1905, pp. 129-189. A more complete discussion of the historical
evolution of the equatorium is given in Derek J. Price, _The
equatorie of the planetis_, Cambridge (Eng.), 1955, pp.
119-133.
[23] E. Wiedemann, and F. Hauser, "Über die Uhren im Bereich d.
islamischen Kultur," _Nova Acta; Abhandlungen der königliche
Leopoldinisch-Carolinische Deutsche Akademie der Naturforscher
zu Halle_, 1915, vol. 100, no. 5.
[24] E. Wiedemann, and F. Hauser, _Die Uhr des Archimedes und
zwei andere Vorrichtungen_, Halle, 1918.
[25] The manuscripts in question are as follows: Gotha, Kat. v.
Pertsch. 3, 18, no. 1348; Oxford, Cod. 954; Leiden, Kat. 3,
288, no. 1414, Cod. 499 Warn; and another similar, Kat. 3, 291,
no. 1415, Cod. 93 Gol.
[26] H. Schmeller, Beiträge zur Geschichte der Technik in der
Antike und bei den Arabern, Erlangen, 1922 (_Abhandlungen zur
Geschichte der Naturwissenschaften und der Medizin_ no. 6).
[27] Once more I am indebted to Professor Loren MacKinney and
Miss Harriet Lattin (see footnote 11) for making their
collections on Gerbert available to me.
[28] Item 198 in Gunther, _op. cit._ (footnote 21). I am
grateful to the authorities of that museum for permission to
reproduce photographs of this instrument.
[29] Sotheby and Co., London, sale of March 14, 1957, lot 154.
The outer rim of the rete has 120 teeth.
[30] The Latin text of the treatise on the Albion, has been
transcribed by Rev. H. Salter and published in R. T. Gunther,
_Early science in Oxford_, Oxford, 1923, vol. 2, pp. 349-370.
An analysis of its design is given in Price, _op. cit._
(footnote 22), pp. 127-130.
[31] Such evidence as there is for the existence and form of
the clock is collected by Gunther, _op. cit._ (footnote 30), p.
49.
[32] I have discussed this new manuscript source in "Two
medieval texts on astronomical clocks," _Antiquarian Horology_,
1956, vol. 1, no. 10, p. 156. The manuscript in question is ms.
230/116, Gonville and Caius College, Cambridge, folios
11ᵛ-14ᵛ = pp. 31-36.
[33] _The Chronicle of Jocelin of Brakelond_ ..., H. E. Butler
(ed.), London, 1949, p. 106.
[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.
[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.
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