AUTHOR'S PREFACE TO THIS EDITION 



reappear in a new edition after long years. But the demand for 

 the book did not cease, and, as the supply was nearly exhausted 

 more than ten years ago, I had to determine on a revision, although 

 the necessary preliminary work had not yet been done. 



As to the general plan of the revision I could not long be in 

 doubt. I could not destroy the shape in which the book had been 

 proved and had won recognition, and I have therefore written it 

 anew on the old plan. The mathematical discussions form, as 

 before, an Appendix which makes no claim to completeness and 

 need not be studied by every reader ; the contents of the book are 

 limited to the same range of phenomena as in the first edition ; 

 the observations which I have taken into consideration belong- 

 partly to mechanical physics and partly to the domains of heat and 

 chemistry. The book has therefore preserved its character, and 

 may perhaps also serve its first purpose. 



I have inserted a series of new theories, as for instance, an 

 explanation on the kinetic theory of the resistance of air and of the 

 reaction of a jet, together with a longer investigation, also new, 

 concerning the influence of the dissociation of the molecules of a 

 vapour upon its viscosity. I should have enlarged the contents of 

 the book in many other directions with pleasure ; I should gladly, 

 for instance, have treated of evaporation in connection with the 

 diffusion of gases and have discussed many other subjects allied to 

 the gaseous theory. But I had to omit much, since the work 

 would have demanded too much time. With the present limita- 

 tion to the old range it has cost very much trouble and very much 

 time to work up the literature of the subject, that has grown 

 mightily in these more than twenty years. 



The first German edition of this book has already had a large 

 sale in England and America. The present English translation 

 will contribute to a still wider dissemination of the book, and will 

 win new friends to the kinetic theory. This I confidently hope, 

 now that by reading the proofs I have seen the loving care with 

 which Mr. Baynes has worked at the translation. By numerous 

 suggestions, too, he has enabled me to remove some errors and to 

 make corrections and additions. For this I here express to him 

 my warmest thanks. 



OSKAR EMIL MEYER 



Breslau: September 1899 



