Notices respecting New Books. 19 9 



important discussion, at the Faraday Society in 1917 opened by 

 Professor A. W. Porter is freely cited. Giving as it does detailed 

 references on all the points discussed, the volume is valuable to the 

 research worker as a guide to the literature of different branches 

 of the subject, as well as to the student seeking only a general 

 knowledge. The latter would probably be grateful if a little more 

 space were devoted to the deduction of some of the formulas 

 given. 



The Theory of Electricity. By Gr. H. Livens, M.A. Cambridge 

 University Press. Pp. viii + 717. Price30s.net. 



In his preface Mr. Livens acknowledges his obligations to 

 Sir Joseph Larmor for permission to make use of notes made at 

 his lectures, and throughout the volume the influence of this great 

 teacher is to be traced. A consequence of this is that space is 

 devoted to the different branches of the subject somewhat in pro- 

 portion to the attention which they have received in the original 

 work of Sir Joseph and his school, and as a result the reader who 

 looks for an account of the new developments of electrical theory 

 is struck by large omissions. For instance, very little space is 

 devoted to the treatment of electric currents in gases and the 

 problems of the motion of ions connected with them (in spite of a 

 diagram showing the effect there is no mention of ionization by 

 collision, and Townsend's name is only mentioned once in the 

 book), to the electron theory of spectral series, or to the reflexion 

 of short electromagnetic waves, while the treatment of relativity, 

 deferred to the last live pages of the book, is very meagre indeed. 

 In view of the success of this theory in interpreting a series of 

 experimental results, and of the attention it has received from 

 many of the best mathematical physicists in Europe, it is worthy 

 of more serious exposition or criticism. Room could have been 

 made for adequate treatment of these and other subjects of present 

 interest by omitting matter of secondary importance only, or 

 matter where a reference to Maxwell's treatise would have sufficed, 

 such as much of the detail of Chapter II. 



We naturally expect to find good chapters on polarized media, 

 on electrostatic stresses and on the electromagnetic field, and we 

 are not disappointed. The treatment of the Maxwellian stress 

 system is particularly satisfactory, and the development of the 

 theory of electromagnetic waves and oscillations is xery complete, 

 especial attention being paid to the field round a Hertzian oscillator. 

 We must also mention an excellent chapter on lnagnetostatics, 

 a rather neglected subject, which includes a short account of the 

 work of Curie, Langevin, and Weiss. 



In general the book appears to suffer from the lack of any very 

 clearly defined plan. It is hard, for instance, to know why the 

 reader should be assumed ignorant of the very elements of vector 

 analysis, but well acquainted with Legemlre functions. Again, 

 after the introductory chapter on vector analysis we should expect 



