ntion of a mechanical escapement, a feature not
found in the European stem in spite of centuries of intensive historical
research and effort.

THE CHINESE TRADITION

For this section I am privileged to draw upon a thrilling research
project carried out in 1956 at the University of Cambridge by a team
consisting of Dr. Joseph Needham, Dr. Wang Ling, and myself.[10] In the
course of this work we translated and commented on a series of texts
most of which had not hitherto been made available in a Western tongue
and, though well known in China, had not been recognized as important
for their horological content. The key text with which we started was
the "Hsin I Hsiang Fa Yao," or "New Design for a (mechanized) Armillary
(sphere) and (celestial) Globe," written by Su Sung in A.D. 1090. The
very full historical and technical description in this text enabled us
to establish a glossary and basic understanding of the mechanism that
later enabled us to interpret a whole series of similar, though less
extensive texts, giving a history of prior development of such devices
going back to the introduction of this type of escapement by I-Hsing and
Liang Ling-tsan, in A.D. 725, and to what seems to be the original of
all these Chinese astronomical machines, that built by Chang Heng _ca._
A.D. 130. Filling the gaps between these landmarks are several other
similar texts, giving ample evidence that the Chinese development is
continuous and, at least from Chang Heng onwards, largely independent of
any transmissions from the West.

So far as we can see, the beginning of the chain in China (as indeed in
the West) was the making of simple static models of the celestial
sphere. An armillary sphere was used to represent the chief imaginary
circles (_e.g._, equator, ecliptic, meridians, etc.), or a solid
celestial globe on which such circles could be drawn, together with the
constellations of the fixed stars. The whole apparatus was then mounted
so that it was free to revolve about its polar axis and another ring or
a casing was added, external and fixed, to represent the horizon that
provided a datum for the rising and setting of the Sun and the stars.

In the next stage, reached very soon after this, the rotation of the
model was arranged to proceed automatically instead of by hand. This was
done, we believe, by using a slowly revolving wheel powered by dripping
water and turning the model through a reduction mechanism, probably
involvin