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, "Ueber die Uhren im Bereich d.
islamischen Kultur," _Nova Acta; Abhandlungen der koenigliche
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, Beitraege 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
11^{v}-14^{v} = 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,"