7 02 SCIENCE PROGRESS 



phenomena to be found, the conductor being merely a more or less unimportant 

 boundary to the medium. Atomic views of electricity could not flourish in such a 

 mental atmosphere, despite the strong suggestion of atomicity conveyed by 

 Faraday's own work on electrolysis. 



With the immense change in the point of view occasioned by the researches of 

 the past two decades, it was natural that the presentation of the subject to the 

 student should suffer some alteration ; even the elementary text-book now presents 

 in its first diaper the "electron theory" as a young and formidable rival to the 

 senile and decaying "single-fluid" and "double-fluid" theories. For the serious 

 student bent on an honours degree (to be followed perhaps by a period of research 

 work) it has been a time of transition, a most uncomforable sort of time indeed for 

 any one who seeks " dry land " on which to rest, without fear of being dislodged 

 by an unexpected wave. The procedure with regard to him has generally been 

 to allow him to study the subject for two or three years in the old, orthodox 

 manner, and then to correct his views by placing in his hands certain recent books, 

 which, assuming a fairly wide knowledge of the older material on the part of the 

 student, proceed to give an account of theory and experimental work developed 

 in recent years. 



Professor Richardson's book is, however, not of this type. It is really an 

 attempt, and an excellent one, to write an advanced text-book of electricity in 

 which the electron is taken as a fundamental postulate from the outset. All our 

 old familiar electrostatic friends, Coulomb, Gauss, Laplace, Poisson, are presented 

 in the light of this new concept. Physical reality is given to all those terrible 

 crevasses, "long-narrow" and "short-wide," in which we used to flounder painfully 

 seeking for the distinction between magnetic "force" and magnetic "induction." 

 A clear conception of the behaviour of a dielectric becomes possible. Indeed, 

 before one quarter of the pages have been passed the author has succeeded in 

 presenting all the older material fully and yet succinctly, in terms of the electron. 

 Lorentz's equations for the electromagnetic field are next dealt with, and the 

 greatest care taken to explain the exact physical meaning of the symbols involved 

 in them. 



It is impossible in a brief notice to deal adequately with the wide range covered 

 in the remaining pages. A very complete account of electron motion, uniform and 

 accelerated, is followed by a chapter on the Aether, and the difficulties raised by 

 the absence of the second order effects of the earth's motion on the speed of 

 light. This leads naturally to an exposition of the principle of Relativity, and 

 some account of the new dynamics which is founded upon it. The electron theory 

 of Magnetism, spectroscopic phenomena, Radiation, and the Planck Quantum 

 hypothesis are fully dealt with. Two excellent chapters on electronic conduction 

 bring the student well within range of the most recent research on this part of the 

 subject. Indeed the "up-to-dateness" of the book is evidenced by the intro- 

 duction of a final chapter on Gravitation, containing the recent speculations of 

 Einstein on that subject and the supposed effect produced by a gravitational field 

 of force on the paths of light-rays. 



The book is based on a course of lectures delivered to graduate students by the 

 author when lecturing at Princeton University. For any one with the necessary 

 mathematical equipment (and how can one proceed very far nowadays in this 

 subject without such equipment ?), this book will serve as an admirably compact 

 and yet very complete account of the subject, leading him directly to many points 

 where research, theoretical and experimental, is proceeding. 



J. R. 



