Monday, May 22, 2006

Tick-tock

Several times over the years I have visited Salisbury Cathedral, eighty miles to the southwest of London and not far from the great megalithic monument at Stonehenge. It is one of the most graceful of medieval cathedrals. As an added attraction, it is home to the oldest mechanical clock in Britain, probably the oldest mechanical clock in the world with most of its original parts and in working order. (It might reasonably be argued that Stonehenge, constructed thousands of years ago in prehistoric times, is the oldest "clock" in Britain; certainly the stones are aligned to mark the peregrinations of the Sun.) The Salisbury cathedral clock was constructed in about the year 1386, of wrought iron, by an unknown craftsperson. It is about as big as a steamer trunk -- an assembly of clunky gears in a boxy iron frame, driven by a falling weight and controlled by an escapement mechanism. The clock has no dial. It strikes the hour on a cathedral bell, as it faithfully did for nearly five hundred years until it was replaced in 1884. In 1956 it was repaired and set up on public display in the nave of the cathedral, where again it whirrs away like some goofy Brobdingnagian windup toy, the great-granddaddy of all subsequent mechanical clocks. This marvelous timekeeper, this ticking correlate of cosmic time, makes a cameo appearance in my Walking Zero: Discovering Cosmic Space and Time Along the Prime Meridian.