The earliest preserved detailed description of mechanical clockwork is due to Richard of Wallingford (d. 1336), abbot St Albans, who was 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 of Wallingford had to design 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.