. 5, 6, 7,
p. 7.

[6] It is interesting to note that the Chinese hodometer was
contemporary with that of Hero and Vitruvius and very similar
in design. There is no evidence whatsoever upon which to decide
whether there may have been a specific transmission of this
invention or even a "stimulus diffusion."

[7] A summary of the content of the manuscript sources,
illustrated by the original drawings, has been published by H.
Alan Lloyd, _Giovanni de Dondi's horological masterpiece,
1364_, without date or imprint (?Lausanne, 1955), 23 pp. It
should be remarked that de Dondi declines to describe the
workings of his crown and foliot escapement (though it is well
illustrated) saying that this is of the "common" variety and if
the reader does not understand such simple things he need not
hope to comprehend the complexities of this mighty clock. But
this may be bravado to quite a large degree.

[8] See, for example, the chronological tables of the 14th
century and the later mentions of clocks in E. Zinner, _Aus der
Fruehzeit der Raederuhr_, Munich, 1954, p. 29 ff. Unfortunately
this very complete treatment tends to confuse the factual and
legendary sources prior to the clock of de Dondi; it also
accepts the very doubtful evidence of the "escapement" drawn by
Villard of Honnecourt (see p. 107). An excellent and fully
illustrated account of monumental astronomical clocks
throughout the world is given by Alfred Ungerer, _Les horloges
astronomiques_, Strasbourg, 1931, 514 pp. Available accounts of
the development of the planetarium since the middle ages are
very brief and especially weak on the early history: Helmut
Werner, _From the Aratus globe to the Zeiss planetarium_,
Stuttgart, 1957; C. A. Crommelin, "Planetaria, a historical
survey," _Antiquarian Horology_, 1955, vol. 1, pp. 70-75.

[9] Derek J. Price, "Clockwork before the clock," _Horological
Journal_, 1955, vol. 97, p. 810, and 1956, vol. 98, p. 31.

[10] For the use of this material I am indebted to my
co-authors. I must also acknowledge thanks to the Cambridge
University Press, which in the near future will be publishing
our monograph, "Heavenly Clockwork." Some of the findings of
this paper are included in shorter form as background material
for that monograph. A brief account of the discovery of this
material has been published by J. Needham, Wang Ling, and Derek
J. Price, "Chin