Photo: Stock Photos from NATALIMA/Shutterstock
Today, candlelight is primarily used for romantic dinners or temporary solutions in power outages. Before electricity, however, the candle had diverse uses. Candles were a critical source of light, they could be affixed to chandeliers or carried around in convenient brass holders. And their wax could be used to seal correspondence for privacy or official approval. Candles could also be used as alarm clocks—a function which is arguably obsolete now, but is an important part of the history of telling time.
The candle clock is an ancient technology. The first recorded reference was in 520 CE in a Chinese poem by You Jiangu. He described six uniform candles of equal weight and thickness—each 12 inches tall. The candles were marked in sections of one inch. Each inch took 20 minutes to burn and an entire candle lasted 4 hours. Enclosed in structures to protect the flame, the candles could be used to gauge the passage of time—a technique perfect for when the sun was not visible.
Other early references to candle clocks exist in Japan during the first millennium CE. Thousands of miles away, King Alfred the Great of England was also thought to use this method in English churches. A candle of any size could be used, so long as the time to burn down was established and regular. Through markings, candles could be subdivided for more incremental measurements of the passing of time.
This method of telling time remained in use through at least the 18th century, despite the increasing ubiquity of traditional wound clocks. In addition to indicating the time, the candles could also serve as alarm clocks. One might stick metal nails into a candle at a desired time interval and place the candle in a metal holder. Once the wax melts at the desired level, the nail falls into the metal base with a clatter, serving as an alarm. This was another option for those seeking to wake up early: factory whistles, street criers, and (of course) roosters could also serve this purpose.
A German candle clock, known as a Kerzenuhr. (Photo: de:Benutzer:Flyout via Wikimedia Commons, CC BY-SA 3.0)
A famous example of an especially intricate candle clock is the clocks of Al-Jazari—a 12th century Muslim engineer and polymath. Known for his water pump and clock inventions, he created a candle clock which used a system of pulleys and weights to transform the continual burning of the candle into time which could be read on a frontward dial. This advanced system …….