REVIEWS 663 



from Electric Systems or Ions in Accelerated Motion and the Mechanical Reac- 

 tions on their Motion which arise from it." The book under review is an extension 

 of the Prize Essay, most of the additional matter being introduced in seven 

 appendices occupying the last 125 pages. As might be anticipated from the title, 

 the essay is deductive and mathematical rather than constructive and physical. 

 The object of the author has been to establish mathematically the foundation for 

 any theory of matter based on the electron, whether it be the electron of Lorentz 

 or that of Bucherer or that of Abraham. 



After a brief discussion of the fundamental equations of the Maxwell- Hertz- 

 Lorentz electron theory, Chapters II. and III. are devoted to the subject of 

 retarded potentials and the point potentials of Lienard and Wiechert. These 

 point potentials are discussed in Chapters IV., V. and VI. and applied to the 

 determination of the electromagnetic field in various special cases of the motion 

 of a point charge. In Chapter VII. the motion is assumed to have a single period 

 whilst in the following chapter more complicated periodic motions are considered 

 and in Chapter IX. non-periodic motions are dealt with. In Chapter VIII. there 

 is also a discussion of the precessional motion of a vibrating system, which is of 

 importance in the theory of the Zeeman effect. Chapter X. is devoted to the 

 field near the orbit of the vibrating charge, the next to the consideration of the 

 equations of motion of the moving charge itself and these are extended in 

 Chapter XII. to a group of electrons. The author states that the appendices, 

 with the exception of the first, are mainly devoted to remedying the defects in 

 Chapters XI. and XII., which, owing to the shortness of time allowed for the 

 essay, were not treated at all adequately. The first appendix deals with the 

 Doppler effect. 



Not the least pleasing feature of the book is the number of clear diagrams by 

 means of which the author illustrates and explains the mathematical processes and 

 results. 



Vector analysis is used throughout and the distinguishing type and symbols 

 adopted are excellent. 



The book is one which can be confidently recommended to all who know some- 

 thing of electromagnetic theory and the methods of vector analysis and wish to 

 understand the recent developments of the electron theory. 



Electric Lighting— and Miscellaneous Applications of Electricity. A Text- 

 book for Technical Schools and Colleges. By William Suddards 

 Franklin. (New York: The Macmillan Company, 1912.) [Pp. 299 

 be. chaps., with 197 figures. 



The title of this book is misleading, as less than 100 pages deal with electric 

 lighting. The contents are best described by the word " miscellaneous " in the 

 sub-title. The chapter contents are as follows : 1, Costs and methods of charging ; 

 2 and 3, wiring and transmission lines ; 4 to 7, photometry, lamps, illumination ; 

 8, electrolysis and batteries ; 9, telegraphs and telephones ; Appendix A, dielectric 

 stresses ; Appendix B, problems. Much of the material is good but the arrange- 

 ment is peculiar and Appendix A gives one the impression of having introduction 

 by mistake. The practical data apply to American conditions and things almost 

 unknown here are given as standard practice. 



Apart from such typographical errors as " killowatt " and " magdetite," we note 

 on p. 87 " two million ergs (or o"2 of a watt) per second." The statement on 

 p. 229 that bridge duplex is specially prevalent in England is hardly correct. 

 Fig. 136 would not work with the batteries as arranged and Fig. 98 is ridiculous. 



