The Astronomical Clock of Richard of Wallingford (d. 1336)

One might imagine that the earliest mechanical clocks would be the simplest. But the evidence suggests otherwise. So fully was timekeeping related to the movements of the heavenly bodies that many early clockmakers aspired to create models of the cosmos, rather than merely aiming to count off the hours, resulting in mechanisms in some respects much more complicated than those of modern clocks. 

A prime example is 'the oldest mechanical clock of which there is detailed knowledge’ (according to the ODNB), devised by the Benedictine abbot St Albans, Richard of Wallingford (d. 1336), the son of a blacksmith, a graduate of Oxford, and a skilled mathematician and astronomer. 

The clock, which was probably eight feet across, showed the Sun and Moon moving across the heavens at variable speeds as well as the locations of the visible stars. The clock face also featured a wheel of fortune and a separate dial showing the ebb and flow of the tides at London Bridge. In order correctly to represent the Sun’s changing rate of motion, Richard devised an oval gear wheel. There was also a half-blackened Moon globe that rotated on its axis as the globe moved round the dial and, by doing so, showed the lunar phase. The lunar globe was so placed that it was automatically drawn under a small eclipsing disc whenever the time was ripe for an eclipse of the Moon.

Commentary. Philipp Nothaft (May-June 2019) and Howard Hotson (May 2024)