[ 343 ] 



XT. On the High-Temperature Standard* of the National Physical Laboratory: 



an Account of a ('omparixon of Platinum Thermometers and 



Thermoj unction* with the Gas Thermometer. 



By J. A. HARKER, D.Sc., Fdlow of Owens College, Manchester, Assistant at the 



National Physical Laboratory. 



Communicated by R. T. GLAZEBROOK, F.R.S.,from the National 



Physical Laboratory. 



Received January 20, Bead February 11, 1904. 



CONTENTS. 



Page 



I. Introduction 314: 



II. The gas thermometer description 345 



III. Gas thermometer details scale, reservoirs, kc 347 



IV. Barometer and auxiliary measurements 348 



V. Preparation of the gases 348 



VI. Filling of the reservoir 350 



VII. Dilatation of the porcelain reservoir 350 



VIII. Pressure coefficient of the reservoirs 351 



IX. The platinum thermometers .352 



X. The resistance box for platinum thermometry 352 



XI. The potentiometer for thermocouple measurements 353 



XII. Standard of electromotive force 350 



XIII. The thermojunctions .357 



XIV. Formula; for thermojunctions .... . 358 



XV. Determination of fixed points 0, 100 and sulphur boiling-point 359 



XVI. Electric furnaces. . . . 



XVII. Furnace correction 362 



XVIII. Exploration of furnace 362 



XIX. Method of calculation of gas thermometer experiments 



XX. Specimen determinations of ice- and steam-points .... 



XXI. Accuracy of constants of gas thermometer 



XXII. Summary of calculation of gas thermometer temperatures. Series II. . . . 368 



XXIII. Method of calculating comparison experiment 



XXIV. Summary of experiments and constants used in calculation . . - 372 

 XXV. Conclusions 377 



XXVI. Table of values of T corresponding to given values of pt for 8= 1 -5. . . . 378 

 XXVII. Table to calculate change in T for a given small change in 8 . . . 

 (369.) 13.8.04 



