OF THK 



UNIVERSITY 



AUTHOE'S PEEFACE 



TO 



THIS EDITION 



THE first edition of this book appeared in 1877, at the time 

 of the most rapid and beautiful development of the kinetic 

 theory of gases. About twenty years before, the founders 

 of the theory, Kronig and Clausius, had explained the 

 expansive tendency of gases, and had calculated their 

 pressure on the assumption that the smallest particles of 

 gases do not repel each other, but are in rapid motion. 

 From the theory based on this supposition not only were 

 the laws of gases, so far as they were then known, deduced 

 in simplest fashion, but ajso new laws, hitherto undreamt 

 of, were discovered, whicc were afterwards confirmed when 



^f 



tested by experiment. These results, which we owe to 

 Maxwell and Clausius, quickly won to the theory many 

 friends and adherents. 



But a deeper insight into the new theory was not then 

 widely possessed, since the mathematical shape of the me- 

 moirs formed a grave obstacle for many readers. I under- 

 took therefore to exhibit the kinetic theory of gases in such 

 a way as to be more easily intelligible to wider circles, and 

 especially to chemists and other natural philosophers to 

 whom mathematics are not congenial. To this end I 

 endeavoured, much more than was otherwise usual, not only 



