Let's Talk Clocks

What constitutes a "clock"? The Latin horologium could refer to a clock or a timepiece of a sundial or the building or structure designed to support any of those.

Modern horology, the study of the measurement of time, distinguishes clocks which mark time by striking something (the word "clock" comes from French cloche, "bell"), whereas a timepiece does not. So a timepiece can mean a watch, a sundial, a clepsydra, or an hourglass, etc.

The sundial was likely the earliest way to measure time: a shadow on a flat surface displays the progression of the sun.

The clepsydra (Greek κλεψύδρα, literally "water thief"), was used in Babylonb, Persia, and Egypt as far back as the 16th century BCE. The simplest form is a bowl or other vessel with a hole from which the water drains, and markings to match drainage levels with the passage of time. The Greco-Roman world devised an in-flow (rather than out-flow) method which, as water filled a container, would trigger a sound, creating an "alarm clock." Water clocks evolved that used gears and escapement mechanisms to produce greater accuracy.

An escapement is a gear mechanism that ticks forward and back to cause another piece to advance. The illustration shows how this works in a pendulum clock, advancing the hands. The use of the escapement was crucial to the development of mechanical clocks, which started to appear in the 14th century in Europe. (Not in the 10th, built by Gerbert d'Aurillac.)

Let's not neglect candle clocks. A Chinese poem written in 520CE by You Joanfu mentions a clock marked so that it could be used while burning to measure the passage of night time. The Anglo-Saxons credit Alfred the Great with creating the candle clock. He used squat candles (<5" high) marked at 1" intervals to mark time.

The hourglass was also a common method of measuring time, the earliest depiction of which is in a 1338 painting by Ambrogio Lorenzetti.

The earliest mechanical clock, a clock that did not use water or sand or candles, that used a predictable motion due to the escapement and a pendulum, did not appear until the early 1300s. Norwich Cathedral had a tower clock constructed in the early 1320s. The first known municipal clock that struck on the hours was in Milan in 1336. Over the next few decades, mechanical clocks appeared all over: Old St. Paul's Cathedral, Salisbury Cathedral (still has many original parts!), Wells Cathedral (still with its original face), etc. Detailed descriptions of clock designs by Richard of Wallingford (1292 - 1336) and Giovanni de Dondi (c.1330 - 1338) still exist, though the many clocks they built are long gone.

A king who developed his own timepieces made from candles? He sounds like someone worth looking into.