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(For a conversion between different temperature scales, see Comparison of temperature scales.)
The Newton scale is a temperature scale devised by Isaac Newton around 1700. Applying his mind to the problem of heat, he elaborated a first qualitative temperature scale, comprising about twenty reference points ranging from "cold air in winter" to "glowing coals in the kitchen fire". This approach was rather crude and problematic, so Newton quickly became dissatisfied with it. He knew that most substances expand when heated, so he took a container of linseed oil and measured its change of volume against his reference points. He found that the volume of linseed oil grew by 7.25% when heated from the temperature of melting snow to that of boiling water.
After a while, he defined the "zeroth degree of heat" as melting snow and "33 degrees of heat" as boiling water. His scale is thus a precursor of the Celsius scale, being defined by the same temperature references. Indeed it is likely that Celsius knew about the Newton scale when he invented his. Newton called his instrument a "thermometer".
- Grigull, U. (1984), "Newton's temperature scale and the law of cooling", Heat and Mass Transfer 18 (4): 195–199, doi:10.1007/BF01007129 .
- Photo of an antique thermometer backing board c. 1758—marked in four scales; the first is Newton's.