- Candle clock
A candle clock is a thin
candle with consistently spaced markings (usually with numbers), that when burned, indicate the passage of periods of time. While no longer used today, candle clocks provided an effective way to tell time indoors, at night, or on a cloudy day. A candle clock could be easily transformed into a timer by sticking a heavy nail into the candle at the mark indicating the desired interval. When the wax surrounding the nail melts, the nail clatters onto a plate below.It is unknown where and when candle clocks were first used. The earliest reference to their use occurs in a Chinese poem by You Jiangu (520 AD). Here, the graduated candle supplied a means of determining time at night. Similar candles were used in
Japan until the early 10th century.The most commonly mentioned candle clock is attributed to
King Alfred the Great ofEngland (c. 878). [citeweb|url=http://www.britannica.com/clockworks/t_candle.html|title=Candle clock] His device consisted of six candles made from 72 pennyweights of wax, each being 12 inches high, of uniform thickness, and divided into 12 sections each of one inch. Each candle burned away completely in four hours, making each marking 20 minutes. The candles were placed for protection inside cases made of a wooden frame with transparent horn panels in the sides. Similar methods of measuring time were used in medieval churches, first by counting the number of candles of a specific size burnt, and later by use of a graduated candle.The most sophisticated candle clocks known to date, however, were those of
Al-Jazari in 1206. It included a dial to display the time and, for the first time, employed a bayonet fitting, a fastening mechanism still used in modern times. [citation|title=Ancient Discoveries , Episode 12: Machines of the East|publisher=History Channel |url=http://www.youtube.com/watch?v=PwGfw1YW9Js|accessdate=2008-09-07]Donald Routledge Hill described one of al-Jazari's candle clocks as follows:Donald Routledge Hill , "Mechanical Engineering in the Medieval Near East", "Scientific American", May 1991, pp. 64-9 (cf. Donald Routledge Hill , [http://home.swipnet.se/islam/articles/HistoryofSciences.htm Mechanical Engineering] )]Notes
References
* Turner, Anthony J. The Time Museum, Volume I, Time Measuring Instruments; Part 3, Water-clocks, Sand-glasses, Fire-clocks
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