The Carcel is a former French unit for measuring the intensity of light. The unit was defined in 1860 as the intensity of a Carcel lamp with standard burner and chimney dimensions, which burnt colza oil  (obtained from the seed of the plant Brassica campestris) at a rate of 42 grams of colza oil per hour with a flame 40 millimeters in height.
- Rowlett, Russ. "Carcel entry". How Many? A Dictionary of Units of Measurement. University of North Carolina at Chapel Hill. Retrieved 2009-05-13.
- "Carcel definition". Webster's Revised Unabridged Dictionary, published 1913 by C. & G. Merriam Co. The Free Dictionary. 2009. Retrieved 2009-05-13.
- Johnston, S.F. (Feb 23, 2004). "History of light and color" (PDF). eknigu Science library. Retrieved 2009-05-13.
- Jail, or cárcel in Spanish
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