About Réaumur
Réaumur was widely used in Europe in the past but is now rarely seen. The Réaumur scale was named after the French physicist René Antoine Ferchault de Réaumur who developed it in the early 18th century. The freezing point of water is 0°Ré and the boiling point 80°Ré. This scale has been almost completely replaced by the Celsius scale.
Despite the Réaumur scale no longer being used, it had a significant impact in the history of temperature measurement.
About Delisle
Developed by French astronomer Joseph-Nicolas Delisle, the Delisle scale was created in the early 18th century. It is a backwards scale that has decreasing values as the temperature rises.
The freezing point of water is 150 degrees and the boiling point is 0 degrees. To convert a temperature from Delisle to Celsius, you can use the formula: Celsius = (150 - Delisle) * 2/3.
In the 18th century the Delisle scale was widely used particularly in Russia but has since been forgotten and replaced by the Celsius scale.