T II E 
LONDON, EDINBURGH, and DUBLIN 
PHILOSOPHICAL MAGAZINE 
AND 
JOURNAL OF SCIENCE. 
[SIXTH SERIES.] 
MARCH iyt)8. 
XXIX. On the Practical Attainment of the Thermodynamic 
Scale of Temperature. — Part III. By J. Rose-Ixxes, 
M.A., B.Sc* 
THE first part of this paper, which was published in the 
Philosophical Magazine some years ago, contained a 
method whereby the thermodynamic correction to a gas- 
thermometer could be calculated from a knowledge of the 
Joule-Thomson effect for the gas, and of its isothermal com- 
pressibility at some one temperature (Phil. Mag. July 1901, 
pp. 131-133). The theory of the method given in that 
paper 1 still believe to be sound ; but the accuracy of the 
final numerical results must depend not merely on the 
soundness of the theory followed, but also on the accuracy 
of the experimental data employed in the calculations. 
Several physicists have lately seen reason to entertain doubts 
concerning the trustworthiness of the measurements of the 
cooling-effect carried out by Joule and Kelvin. I have 
therefore thought it might be of some interest to develop a 
theory of the gas-thermometer in which less reliance is placed 
than formerly on the Joule-Thomson measurements. Not 
that we can afford to neglect the Joule-Thomson measure- 
ments altogether ; every theory of the gas-thermometer is 
obliged to rely on them to some extent. But w r e are not 
obliged to go the length of accepting the absolute values of 
* Communicated by Prof. F. T. Trouton. 
Phil. Jf<>«. S. 6. Vol. 15. No. 87. March 1908. Y 
