vi Preface 



An attempt at an exact treatment of the subject has unfortunately 

 involved the introduction of a considerable quantity of mathematical analysis, 

 but I have kept before me the desire to reduce the amount of analysis to the 

 minimum consistent with efficiency, in the hope of making as much of the 

 book as possible intelligible to readers who are not trained mathematicians. 



I have also paid considerable attention to estimates of numerical values, 

 to experimental results, and to the physical interpretation of the phenomena 

 discussed, my ambition being to endow the subject with more life than 

 would have been possible if it had been treated solely as a dynamical 

 problem. As regards these parts of my work, I have been fortunate in re- 

 ceiving advice and criticism from Mr H. A. Wilson and Mr 0. W. Richardson, 

 Fellows of Trinity College. I therefore venture to hope that there are no 

 serious inaccuracies in the more physical parts of the book. It will of course 

 be understood that the book makes no claim to give anything like a full 

 account of experimental results. Such results as are quoted are meant as 

 illustrations only. The reader who wishes for a fuller account of experi- 

 / mental work is referred to Meyer's Kinetic Theory of Oases or Weinstein's 

 Thermodynamik und Kinetik der Korper. From both these books, as also 

 from Travers' Experimental Study of Gases, I have borrowed largely. In the 

 more abstract parts of the subject I have made constant use of the writings 

 of Maxwell, Rayleigh and Tait, of Boltzmann's Vorlesungen ilber Gastheorie, 

 of the papers of the same author in the Wiener Sitzungsberichte, and of 

 Kirchhoff 's Vorlesungen ilber die Theorie der Warme. To all these I express 

 my indebtedness. 



It remains only to record my thanks to all who have helped me with 

 suggestions and criticisms, and to the staff of the University Press from 

 whom I have received every possible assistance and courtesy during the 

 printing of the book. 



J. H. JEANS. 



November, 1904. 



