Chemistry and Physics. 193 



10. Studies in Radioactivity ; by W. H. Bragg. Pp. x, 196, 

 with 70 figures. London, 1912 (Macmillan and Co.). — This vol- 

 ume of " Macmillan's Science Monographs " deals mainly with the 

 phenomena attending the passage of a, f}, y and Arrays through 

 matter. The researches of the author have been so bound up 

 with the work of other investigators that, of necessity, the vol- 

 ume is not restricted to a systematic acconnt of Bragg's experi- 

 ments but it is limited only by the confines of the field in which 

 the inquiries have been made. It is manifestly impossible to do 

 justice to the argument of the text in the space at our disposal. 

 Suffice it to say that, as is well-known, Bragg interprets the 

 experimental evidence as showing the non-existence of true sec- 

 ondary radiation and that AT and y rays are corpuscular in nature 

 since they are, in a certain sense, completely interchangeable 

 with the moving electron. The investigations of the author are 

 so important, his style is so lucid and pleasing, and the diagrams 

 and type are so clear, that the book merits the attention of all 

 students of radio-activity. h. s. u. 



11. Electric Lighting ; by William Suddards Franklin. 

 Pp. viii, 299, with 203 figures. New York, 1912 (The Macmillan 

 Co.). — It seems desirable to point out the relationship existing 

 between this book and certain earlier volumes by the same author. 

 The present volume is intended to be a companion to " Dynamos 

 and Motors " by Franklin and Esty. In these two volumes the 

 physical principles underlying operating engineering rather than 

 the principles of design have received especial emphasis. Also, 

 the ground covered in these two books is not coextensive with 

 the material presented in the author's " Elements of Electrical 

 Engineering." 



Some of the topics discussed in the volume to which this notice 

 primarily refers are : installation and operation costs, electric 

 distribution and wiring, alternating-current lines, photometry, 

 electric lamps, lamp shades and reflectors, interior and street 

 illumination, electrolysis and batteries, telegraph and telephone 

 systems, and dielectric stresses. The practical value of the text 

 is enhanced by numerous bibliographical references. The figures 

 are clear-cut and to the point, and the manner of presentation has 

 the same characteristics as all of the author's works, namely, 

 lucidity and practicability. Appendix B is a list of 63 problems 

 classified according to the respective chapters. h. s. u. 



12. Lehrbuch der Optik ; by Paul Drude. Third edition, 

 revised by E. Gehrcke. Pp. xvi, 548, Leipzig, 1912 (S. Hirzel). 

 —The latest edition of this standard text-book differs but little 

 from the second (see this Journal, vol. xxiii, p. 146, 1907). Two 

 new articles, dealing respectively with Stokes's theory of aberra- 

 tion and with photochemical processes in gases, have been added. 

 The bibliographical and explanatory foot-notes have been changed 

 to conform to the recent developments of the subject. The num- 

 ber of pages, however, has only been increased by ten. h. s. tj. 



