Gene Mechtly asked in USMA 18552: >What is the difference between the historical definition >of the centigrade temperature scale and the modern Celsius scale?
And then went on to explain the difference. >In 1742, Anders Celsius published a paper titled (after translation) >"Observations on Two Constant Degrees on One Thermometer" in the >Transactions of the Swedish Academy of Sciences. > >The *two constants* were the ice point and the boiling point of water, >separated by exactly 100 degrees on that "centigrade" scale. Celsius >chose the boiling point as the zero on his original scale. > >On the other hand, the modern Celsius scale has *only one* fixed point, >a zero at 273.15 K, and an increment (unit) of temperature difference >identical to 1 K, as Jim Frysinger has explained. > >Thus, the original "centigrade" scale was, in fact, *different* from the >modern Celsius scale. >However, the definition of the original centigrade scale, and its >immediate successor with the zero reset at the ice point, were effectively >discarded by a series of resolutions by the CGPM as Joe has explained. If anyone refers to a temperature before 1948 as Celsius, as was common in Eastern Europe, or refers to a temperature after 1948 as "centigrade", they are only excusably wrong linguisticly, The physical definitions were as Gene has explained. Joseph B.Reid 17 Glebe Road West Toronto M5P 1C8 TEL. 416-486-6071
