The point of this paper is that such a complex exists, cutting across
the histories of the clock, the various types of astronomical machines,
and the magnetic compass, and including the origin of "self-moving
wheels." It seems to trace a path extending from China, through India
and through Eastern and Western Islam, ending in Europe in the Middle
Ages. This path is not a simple one, for the various elements make their
appearances in different combinations from place to place, sometimes one
may be dominant, sometimes another may be absent. Only by treating it as
a whole has it been possible to produce the threads of continuity which
will, I hope, make further research possible, circumventing the blind
alleys found in the past and leading eventually to a complete
understanding of the first complicated scientific machines.

FOOTNOTES:

[1] This traditional view is expressed by almost every history
of horology. An ultimate source for many of these has been the
following two classic treatments: J. Beckmann, _A history of
inventions and discoveries_, 4th ed., London, 1846, vol. 1, pp.
340 ff. A. P. Usher, _A history of mechanical inventions_, 2nd
ed., Harvard University Press. 1954, pp. 191 ff., 304 ff.

[2] There is a considerable literature dealing with the later
evolution of perpetual motion devices. The most comprehensive
treatment is H. Dircks, _Perpetuum mobile_, London, 1861; 2nd
ser., London, 1870. So far as I know there has not previously
been much discussion of the history of such devices before the
renaissance.

[3] For the early history of gearing in the West see C.
Matschoss, _Geschichte des Zahnrades_, Berlin, 1940. Also F. M.
Feldhaus, _Die geschichtliche Entwicklung des Zahnrades in
Theorie und Praxis_, Berlin, 1911.

[4] A general account of these important archaeological objects
will be published by J. Needham, _Science and civilisation in
China_, Cambridge, 1959(?), vol. 4. The original publications
(in Chinese) are as follows: Wang Chen-to, "Investigations and
reproduction in model form of the south-pointing carriage and
hodometer," _National Peiping Academy Historical Journal_,
1937, vol. 3, p. 1. Liu Hsien-chou, "Chinese inventions in
horological engineering," _Ch'ing-Hua University Engineering
Journal_, 1956, vol. 4, p. 1.

[5] For illustrations of intermeshing worms in Indian cotton
mills, see Matschoss, _op. cit._ (footnote 3), figs