Marie-Antoinette's Watch: Adultery, Larceny & Perpetual Motion

Chapter 5

The sundial was accurate and virtually foolproof - after all, its power source rose in the morning - but it was not always portable, and its transmission system (a stick) and register (a shadow) were imprecise. A cloud or an errant breeze could turn a carefully constructed sundial into a patch of empty earth and the sun had a pesky way of often hiding behind clouds. A sundial also required a great deal of trust that the motion of the heavens was regular and that the sun would never wind down - a tall order for early astronomers. And, of course, sundials didn't work at night.

In order to maintain prayer schedules even after the sun had set, priests in ancient Egypt employed another simple system: a water clock. The clock consisted of a bowl with a small hole that released water at a pre-defined rate. Like an hourglass, it would mark the passage of time by draining away, and it had the added benefit of being readable in the dark. A night watchman guarding the pharaoh's palace could simply dip his finger into the bowl to see how much time had elapsed. As the bowl emptied - or filled, in another bowl of water, and sank - the changing water level caused chimes to sound or made a tapping noise, thus creating the first mechanical register, the horological term for a read-out.

The Greeks called these devices clepsydras, or water thieves, and they began to take more fanciful shapes and offer a number of unique time-telling features - what horologers now call "complications." A clepsydra known as the Horologion, created by a Macedonian astronomer named Andronicus of Cyrrhus in around 50 BC, showed astronomers as well as townsfolk the time during the day, and at night also provided an indicator for the direction of the wind.

Another clock, devised by Hero of Alexandria around 150 BC, was powered by water filling a drum, and marked the hour using a human figure that pointed an arrow at a meter drawn on a cylinder. As the figure moved upwards it pushed a little water into a circular set of troughs that emptied once a year and adjusted the hour slightly to reflect the differing lengths of days (thereby anticipating leap years). This miraculous invention was called the Ctesibius, after the Greek father of pneumatics, and was one of the first clocks to take into consideration the difference between solar time and man-made twenty-four-hour time. The clock predated similar technology by 1600 years and showed an impressive understanding of the sun's motion. This handling of the "equation of time," or the failure of the day to fit neatly into twelve hour increments, was a dauntingly complex problem that took centuries to solve mechanically, yet it was done by an ancient Greek using only water and some plumbing.

The first modern mechanical clock appeared in the eleventh century, when Su Song, a Chinese official, created a clepsydra that looked less like the primitive bowl-and-basin system used for centuries than an early grandfather clock. It still used water, but as a power source, rather than an indicator. As the liquid flowed downward through a series of buckets, the motion of the stream would power the clock. The clock itself consisted of a complex mash of gears, hands, and bells. It could chime the hours and had animated figures that moved and danced at pre-set times.

But even when used as a power source, water, like the sun, had obvious limitations. As the liquid flowed through the machine, friction caused some buckets to refill faster or more slowly than others. To remedy this, a number of solutions were tried to control the rotation of the wheel - or transmission system - and ensure that it "escaped" at exactly the right period. Some escapements used spinning regulators, while others used weights or even pools of mercury that slowly filled portions of the wheel as it turned. Nothing, however, could be done about the power source freezing in the winter or evaporating under the summer sun. You'll notice that many early water clocks first appeared in temperate climates that weren't too hot or too cold. Northerners, while enamored with the idea of the water clock, would have to think of something that wouldn't be affected by the vagaries of weather.