ese astronomical clockwork," _Nature_, 1956,
vol. 177, pp. 600-602.

[11] For these translations from classical authors I am
indebted to Professor Loren MacKinney and Miss Harriet Lattin,
who had collected them for a history, now abandoned, of
planetariums. I am grateful for the opportunity of giving them
here the mention they deserve.

[12] A. G. Drachmann, "The plane astrolabe and the anaphoric
clock," _Centaurus_, 1954, vol. 3, pp. 183-189.

[13] A fuller description of the anaphoric clock and cognate
water-clocks is given by A. G. Drachmann, "Ktesibios, Philon
and Heron," _Acta Historica Scientiarum Naturalium et
Medicinalium_, Copenhagen, 1948, vol. 4.

[14] First published by O. Benndorf, E. Weiss, and A. Rehm,
_Jahreshefte des oesterreichischen archaeologischen Institut in
Wien_, 1903, vol. 6, pp. 32-49. I have given further details of
its construction in _A history of technology_, ed. Singer,
Holmyard, and Hall, 1957, vol. 3, pp. 604-605.

[15] L. Maxe-Werly, _Memoires de la Societe Nationale des
Antiquaires de France_, 1887, vol. 48, pp. 170-178.

[16] The first definitive account of the Antikythera machine
was given by Perikles Rediadis in J. Svoronos, _Das Athener
Nationalmuseum_, Athens, 1908, Textband I, pp. 43-51. Since
then, other photographs (mostly very poor) have appeared, and
an attempt at a reconstruction has been made by Rear Admiral
Jean Theophanidis, _Praktika tes Akademias Athenon_, Athens,
1934, vol. 9, pp. 140-149 (in French). I am deeply grateful to
the Director of the Athens National Museum, M. Karouzos, for
providing me with an excellent new set of photos, from which
figures 6-8 are now taken.

[17] H. Diels Ueber die von Prokop beschriebene Kunstuhr von
Gaza, _Abhandlungen, Akademie der Wissenschaften_, Berlin,
Philos.-Hist. Klasse, 1917, No. 7.

[18] L. A. Mayer, _Islamic astrolabists and their works_,
Geneva, 1956, p. 62.

[19] The translation which follows is quoted from J. Beckmann,
_op. cit._ (footnote 1), p. 349.

[20] E. Wiedemann, "Ein Instrument das die Bewegung von Sonne
und Mond darstellt, nach al Biruni," _Der Islam_, 1913, vol. 4,
p. 5.

[21] I acknowledge with thanks to the Curator of that museum
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_,