Delisle (°De)
The Delisle scale is a historical temperature scale invented in 1732 by French astronomer Joseph-Nicolas Delisle. Uniquely among temperature scales, it runs in reverse: higher numbers indicate colder temperatures. Water boils at 0°De and freezes at 150°De. The scale was used in Russia for nearly a century before being replaced by Celsius.
Definition
On the Delisle scale, water boils at 0°De and freezes at 150°De at standard atmospheric pressure. To convert Delisle to Celsius: °C = 100 − °De × 2/3. To convert Celsius to Delisle: °De = (100 − °C) × 3/2. Absolute zero is 559.725°De. The scale has no modern standardised definition and is of purely historical interest.
History
Joseph-Nicolas Delisle created his scale in 1732 while working at the Russian Academy of Sciences in St. Petersburg. He originally set the boiling point of water as the zero point and measured downward from there, with each degree representing a contraction of mercury in his thermometer. Anders Celsius may have been influenced by this inverted approach when he created his own scale (also initially inverted) in 1742. The Delisle scale was the standard temperature scale in Russia until 1790, when it was replaced by the Réaumur scale, which was later superseded by Celsius.
Common Uses
The Delisle scale has no modern applications. It is studied in the history of science and occasionally appears in physics education as an example of alternative temperature scales. Meteorological records from 18th-century Russia sometimes reference Delisle temperatures, requiring conversion for modern analysis.
Did You Know? Facts About Delisle
- The Delisle scale is the only commonly known temperature scale that runs backwards - higher numbers mean lower temperatures.
- Delisle invented his scale in St. Petersburg, Russia, where it was used as the national standard for nearly 60 years.
- On the Delisle scale, room temperature (20°C) is 120°De.
- Anders Celsius may have been inspired by Delisle's inverted scale when he created his own (also initially inverted) scale in 1742.
- The Delisle scale is one of six historical temperature scales still occasionally referenced in physics textbooks, alongside Celsius, Fahrenheit, Kelvin, Réaumur, and Rømer.