0 years of history on three continents._

THE AUTHOR: _Derek J. de Solla Price wrote this paper while serving as
consultant to the Museum of History and Technology of the Smithsonian
Institution's United States National Museum._

In each successive age this construction, having become
lost, is, by the Sun's favour, again revealed to some one
or other at his pleasure. (_S[=u]rya Siddh[=a]nta_, ed.
Burgess, xiii, 18-19.)

THE HISTORIES of the mechanical clock and the magnetic compass must be
accounted amongst the most tortured of all our efforts to understand the
origins of man's important inventions. Ignorance has too often been
replaced by conjecture, and conjecture by misquotation and the false
authority of "common knowledge" engendered by the repetition of
legendary histories from one generation of textbooks to the next. In
what follows, I can only hope that the adding of a strong new trail and
the eradication of several false and weaker ones will lead us nearer to
a balanced and integrated understanding of medieval invention and the
intercultural transmission of ideas.

For the mechanical clock, perhaps the greatest hindrance has been its
treatment within a self-contained "history of time measurement" in which
sundials, water-clocks and similar devices assume the natural role of
ancestors to the weight-driven escapement clock in the early 14th
century.[1] This view must presume that a generally sophisticated
knowledge of gearing antedates the invention of the clock and extends
back to the Classical period of Hero and Vitruvius and such authors
well-known for their mechanical ingenuities.

Furthermore, even if one admits the use of clocklike gearing before the
existence of the clock, it is still necessary to look for the
independent inventions of the weight-drive and of the mechanical
escapement. The first of these may seem comparatively trivial; anyone
familiar with the raising of heavy loads by means of ropes and pulley
could surely recognize the possibility of using such an arrangement in
reverse as a source of steady power. Nevertheless, the use of this
device is not recorded before its association with hydraulic and
perpetual motion machines in the manuscripts of Ri[d.]w[=a]n, _ca._ 1200,
and its use in a clock using such a perpetual motion wheel (mercury
filled) as a clock escapement, in the astronomical codices of Alfonso
the Wise, King of Castile, _ca._ 1272.

The second invention, that of t