In preparing a tentative proposal for a new text of the introduction it soon became evident that the other three parts of the text would also profit by a revision. 4 As soon as this resolution had been adopted it was pointed out that it would be necessary to revise the introduction of the text of the International Temperature Scale of 1948 to conform with the action just taken. This kind of definition was what Kelvin, in 1854, had said “must be adopted ultimately.” This resolution was recommended by the International Committee and adopted by the Tenth General Conference. In 1954 the Advisory Committee proposed a resolution redefining the Kelvin thermodynamic scale by assigning a value to the triple point of water. The third was to increase the value for the second radiation constant to bring it nearer to the value derived from atomic constants. Another was to specify Planck’s radiation formula instead of Wien’s formula so the scale would be consistent with the thermodynamic scale above the gold point. One was to increase the value assigned to the silver point by 0.3 degree, merely to make the scale more uniform. In the revision there were only three changes which affected values of temperatures on the scale. 3 The revised scale was designed to conform as nearly as practicable to the thermodynamic scale as then known, while incorporating certain refinements, based on experience, to make the scale more uniform and reproducible than its predecessor. 2 At this time the General Conference also adopted the designation of degree Celsius in place of degree Centigrade or Centesimal. The International Committee recommended this revision to the Ninth General Conference which adopted it. In 1948 a revision of the International Temperature Scale was prepared by the Advisory Committee and proposed to the International Committee. The Advisory Committee on Thermometry was authorized in 1933 and first met in 1939. The International Committee now has six advisory committees of specialists most of whom represent large national laboratories.

It consists of 18 scientists, only one from any one nation, and it normally meets every two years. The International Committee is the executive body elected by the General Conference. The General Conference normally meets every six years, and at those times may adopt recommendations submitted by the International Committee. The General Conference on Weights and Measures is the official international body now representing 36 nations that subscribe to the Treaty of the Meter. A practical scale, named the International Temperature Scale, was finally agreed upon, was recommended to the Seventh General Conference on Weights and Measures by its International Committee on Weights and Measures, and was adopted in 1927. As early as 1911 the directors of the national laboratories of Germany, Great Britain, and the United States agreed to undertake the unification of the temperature scales in use in their respective countries. An internationally accepted scale on which temperatures can be measured conveniently and accurately is necessary for science and industry.

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