First candle clock No one knows who invented the candle clock or when it first appears in history, but the earliest known reference to one is in a Chinese poem by You Jiangu, which is dated AD 520. Candle clocks work very much like incense clocks. The wax for each candle is allotted so that it will burn at a constant rate within a specific period. For instance, You Jiangu’s candles were designed to burn completely in four hours. The candle is divided into sections, such as twelve sections, each one measuring one inch, and, in the case of You Jiangu’s clock, representing 20 minutes. Thus, each marking represents a certain number of minutes. As the candle burns down to each marker, the owner can keep track of the time that has passed. Sometimes a weight, such as a nail, was attached to the candle at a certain marker. When the wax burned down, the weight would clatter to the floor, functioning as an alarm. Candle clocks were used before there were mechanical clocks. They provided a relatively reliable way to tell time indoors, especially at night and cloudy days. Read more about combustion clocks in the Clocktime article The first timekeepers: Telling time before the pendulum clock. Image Credits (Artist) Farruk ibn Abd al-Latif (CB), Folio from Kitab fi ma`arifat al-hiyal al-handisaya, 1206, Accession number: F1930.71. Purchase — Charles Lang Freer Endowment, Freer Gallery of Art and Arthur M. Sackler Gallery, Smithsonian Institution, https://collections.si.edu/search/detail/edanmdm:fsg_F1930.71 Candle clock ca. 18th century; Candle in front of scale, engraved in metal applique/holder hung on the wall. de:Benutzer:Flyout, CC BY-SA 3.0, via Wikimedia Commons, https://commons.wikimedia.org/wiki/File:Kerzenuhr.jpg
