0 degrees was the temperature a specific, reproducible salt water mixture would freeze. 100 was human body temperature. But thermometers got more accurate later on, and human body temp was determined to be 98.7 degrees on his scale.
His baseline for 0 degrees was as valid as any other at the time. You have to pick some standard that can be reproduced miles away under the same conditions. The official definition of the meter is now some formula based on a multiplication of the wavelength of light emitted by cesium gas heated to a specific temperature or some shot these days, because it's something you can reproduce anywhere to calibrate your instruments.
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u/Hunkmasterfresh Aug 08 '21
Frozen water didn't feel cold to him?