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{{Short description|Way of measuring time using a burning candle}}
[[Image:Kerzenuhr.jpg|thumb|An example of a German candle clock]]
A '''candle clock''' is a thin candle with consistently spaced marking that, when burned, indicates 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.

== History ==
It is unknown where and when candle clocks were first used. The earliest reference to their use to 
occurs in a [[Chinese poetry|Chinese poem]] by You Jiangu (AD 520).<ref name="nrich_maths_org">{{cite web|last1=Rodgers|first1=Leo|title=A Brief History of Time Measurement|url=https://nrich.maths.org/6070|website=NRICH|accessdate=4 November 2017}}</ref> Here, the graduated candle supplied a means of determining time at night. Similar candles were used in [[Japan]] until the early 10th century.

You Jiangu's device consisted of six candles made from 72 pennyweights (24 grains each), 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.<ref name="nrich_maths_org" /> 

Similar methods of measuring time were used in medieval churches.{{citation required|date=June 2021}} The invention of the candle clock was attributed by the [[Anglo-Saxons]] to [[Alfred the Great]], king of [[kingdom of Wessex|Wessex]]. The story of how the clock was created was narrated by [[Asser]], who lived at Alfred's court and became his close associate.{{sfn|Asser|1983|p=10}} Alfred used six candles, each made from 12&nbsp;[[pennyweight]]s of wax, and made to be {{convert|12|in|cm}} high and of a uniform thickness. The candles were marked at intervals of an [[inch]]. Once lit, they were protected from the wind by being placed in a lantern made of wood and transparent [[Horn (anatomy)|horn]]. It would have taken 20&nbsp;minutes to burn down to the next mark; the candles, burning one after the other, lasted for 24 hours.{{sfn|Asser|1983|p=108}}

=== Al-Jazari ===
[[Image:Al-Jazari - A Candle Clock.jpg|thumb|right|[[Al-Jazari]]'s candle clock]]

[[Al-Jazari]] described a candle clock in 1206.<ref name=Hill2/> It included a [[Dial (measurement)|dial]] to display the time and, for the first time, employed a [[Bayonet mount|bayonet fitting]], a [[Fastener|fastening mechanism]] still used in modern times.<ref>{{citation|title=Ancient Discoveries, Episode 12: Machines of the East|date=28 July 2008 |publisher=[[History (U.S. TV channel)|History Channel]]|url=https://www.youtube.com/watch?v=PwGfw1YW9Js |archive-url=https://ghostarchive.org/varchive/youtube/20211221/PwGfw1YW9Js |archive-date=2021-12-21 |url-status=live|accessdate=2008-09-07}}{{cbignore}}</ref> The English engineer and historian [[Donald Routledge Hill]] described one of al-Jazari's candle clocks as follows:
{{quotation |The candle, whose rate of burning was known, bore against the underside of the cap, and its wick passed through the hole. Wax collected in the indentation and could be removed periodically so that it did not interfere with steady burning. The bottom of the candle rested in a shallow-dish that had a ring on its side connected through pulleys to a counterweight. As the candle burned away, the weight pushed it upward at a constant speed. The automata were operated from the dish at the bottom of the candle.<ref name=Hill2>[[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] {{webarchive |url=https://web.archive.org/web/20071225091836/http://home.swipnet.se/islam/articles/HistoryofSciences.htm |date=December 25,2007 }})</ref>}}

==References==
<references/>

==Sources==
* {{cite book |last1=Asser |author1-link=Asser |editor1-last=|translator-last1=Keynes |editor1-first=|translator-first1=Simon |editor2-last=|translator-last2=Lapidge |editor2-first=|translator-first2=Michael |title=Alfred the Great: Asser's Life of King Alfred and other contemporary sources |date=1983 |publisher=Penguin Books |location=London; New York |isbn=978-01404-4-409-4 |url=https://archive.org/details/alfredgreatasser0000asse/page/n5/mode/2up |url-access=registration |archive-date=|orig-year            =before 909}}
* Turner, Anthony J. The Time Museum, Volume I, Time Measuring Instruments; Part 3, Water-clocks, Sand-glasses, Fire-clocks

{{DEFAULTSORT:Candle Clock}}
[[Category:Candles]]
[[Category:Chinese inventions]]
[[Category:Clocks]]
[[Category:Japanese inventions]]

[[ru:Огненные часы#Свечные часы]]