Mercury-in-glass thermometer ushered in a new era of accuracy and precision in thermometry, and is still to this day regarded as one of the most accurate thermometers available. The thermometer was used by the originators of the Fahrenheit and Celsius scales. Anders Celsius, a Swedish scientist, devised the Celsius scale, which was described in his publication "The origin of the Celsius temperature scale" in 1742. Celsius used two fixed points in his scale: the temperature of melting ice and the temperature of boiling water. This wasn't a new idea, since Isaac Newton was already working on something similar. The distinction of Celsius
Temperature which implies Since the first function is independent of "T", this temperature must cancel on the right side, meaning "f"("T","T") is of the form "g"("T")/"g"("T") (i.e. "f"("T","T") = "f"("T","T")"f"("T","T") = "g"("T")/"g"("T")· "g"("T")/"g"("T") = "g"("T")/"g"("T")), where "g" is a function of a single temperature. A temperature scale can now be chosen with the property that Substituting (4) back into (2) gives a relationship for the efficiency in terms of temperature: For "T" = 0 K the efficiency is 100% and that efficiency becomes greater than 100% below 0 K. Since an efficiency greater than 100% violates the first law of thermodynamics,