PREFACE. 



through the printer's hands, it occurred to me that 

 it might be well to reissue in a collected form 

 several other lectures and addresses of a popular 

 character, which I have given from time to time, 

 and which could not find a fitting place in my 

 " Reprint of Mathematical and Physical Papers," 

 now being published by the Cambridge University 

 Press. After consideration it was decided to 

 change the character of the proposed volume 

 " On Capillarity," and to increase its size and 

 make it the first of a series of three volumes to 

 constitute a reprint of all my popular lectures 

 and addresses. 



The order in which the various articles are 

 arranged, both in the present volume and in those 

 which are to follow, is, generally speaking, according 

 to the subject matter. Thus in the present volume 

 are included lectures concerned with the ultimate 



