e used to bridge this gap between the first use of gears and the
fully-developed mechanical clock we must examine the other side of this
gap. Recent research on the history of early mechanical clocks has
demonstrated certain peculiarities most relevant to our present
argument.

THE EUROPEAN TRADITION

If one is to establish a _terminus ante quem_ for the appearance of the
mechanical clock in Europe, it would appear that 1364 is a most
reasonable date. At that time we have the very full mechanical and
historical material concerning the horological masterpiece built by
Giovanni de Dondi of Padua,[7] and probably started as early as 1348. It
might well be possible to set a date a few decades earlier, but in
general as one proceeds backwards from this point, the evidence becomes
increasingly fragmentary and uncertain. The greatest source of doubt
arises from the confusion between sundials, water-clocks, hand-struck
time bells, and mechanical clocks, all of which are covered by the term
_horologium_ and its vernacular equivalents.

Temporarily postponing the consideration of evidence prior to _ca._
1350, we may take Giovanni de Dondi as a starting point and trace a
virtually unbroken lineage from his time to the present day. One may
follow the spread of clocks through Europe, from large towns to small
ones, from the richer cathedrals and abbeys to the less wealthy
churches.[8] There is the transition from the tower clocks--showpieces
of great institutions--to the simple chamber clock designed for domestic
use and to the smaller portable clocks and still smaller and more
portable pocket watches. In mechanical refinement a similar continuity
may be noted, so that one sees the cumulative effect of the introduction
of the spring drive (_ca._ 1475), pendulum control (_ca._ 1650), and the
anchor escapement (_ca._ 1680). The transition from de Dondi to the
modern chronometer is indeed basically continuous, and though much
research needs to be done on special topics, it has an historical unity
and seems to conform for the most part to the general pattern of steady
mechanical improvement found elsewhere in the history of technology.

[Illustration: Figure 3.--GERMAN WALL CLOCK, PROBABLY ABOUT 1450,
showing the degeneration in complexity from that of de Dondi's clock.]

Most remarkable however is the earliest period of this seemingly steady
evolution. Side by side with the advances made in the earliest period
extending for less