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III. On the Measurement of Temperature. Part 1 .—On the Pressure Coefficients 
of Hydrocjen and Helium at Constant Volume and at diferent Initial 
Pressures. Part IL —On the Vapour Pressures of Liquid Oxygen at 
Temperatures heloio its BoUiny-Point on the Constant- Volume Hydrogen 
and Helium Scales. Part III. — On the Vapour Pressures of Liquid 
Hydrogen at Temqjeratures below its Boiling-Point on the Constant- Illume 
Hydrogen and Helium Scales. 
By Moiirls W. Tiiaveks, D.Sc., Fellow of University College, London, 
Geoege Sexter, B.Sc., and Adriex Jaquerod, D.Sc. 
Communicated by Professor William Ramsay, F.R.S. 
lieceived June 19,—Read June 19, 1902. 
[Plate 1.] 
PART L 
On the Pressure Coefficients of Hydrogen and Helium at Constant Volume and at 
different initied Pressures. 
By Morris W. Travers, D.Sc., Fellow of University College, London, 
and Adrien Jaquerod, D.Sc. 
Contents, 
1. Introduction. 
2. Suitable thermometric substances. 
3. Previous measurements of the pressure coefficients of liydrogen and helium . 
4. Accuracy of the results. 
5. Apparatus employed in the research. The barometer. 
6. The constant-volume thermometer. 
7. The calibration of the bulb. 
8. The dead-space. . 
9. The stem of the thermometer. . 
10. The volumes of the bulb, stem, and dead-space. 
11. The manometer and its connection with the dead-space, Ac. 
12. The introduction of gas into the thermometer. 
13. The scale. 
14. The temperature of the mercury column... 
15. The measurement of the pressure on the gas in the thermometer . . . . 
16. The ice-point.. 
VOL. CC.—A 323 
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