662 Scientific Intelligence. 



and number in parallel have been changed from C, K, m, and n, 

 to i, C, s, and p respectively. Appendix B has been brought up 

 to date and the appendix on the Clark cell omitted. The number 

 of problems for solution by the student has been increased from 

 246 to 291. Since we have found this text very useful in our 

 classes in the past we expect to obtain even better results with 

 the new edition during the present winter. h. s. u. 



10. A Treatise on Light; by R. A. Houstoun. Pp. xi, 478, 

 with 328 figures. London, 1915 (Longmans, Green and Co.). — 

 The author says in the preface that " This book is intended for 

 students who have been through a first year's physics course and 

 who are proceeding further with the study of light. It differs from 

 other books on light by a more systematic treatment, also by deal- 

 ing with the full scope of the subject and including the results of 

 recent investigations. A good knowledge of elementary mathe- 

 matics is assumed. The calculus is used, but I hope that the 

 results obtained by its aid will be intelligible to those who cannot 

 follow the intermediate steps, and in any case the greater part of 

 the book is free from it." 



The text is conveniently divided into four Parts which deal 

 respectively with geometrical optics (113 pages), physical optics 

 (114 pages), spectroscopy and photometry (129 pages), and mathe- 

 matical theory (100 pages). The chief topics discussed in Part I 

 are the theory of spherical mirrors, of thin and thick lenses, and 

 of systems of lenses, the defects of images, the determination of 

 the constants of mirrors and lenses, optical instruments, and the 

 determination of indices of refraction. The method of rays is 

 used throughout. Part II deals with the velocity of light, inter- 

 ference, diffraction, polarization, double refraction, the propaga- 

 tion of light in crystals, optical rotation, and the analysis of 

 polarized light. The third division of the text gives an account 

 both of the historic development of spectroscopy and of all the 

 most important results obtained by spectroscopic methods. The 

 ultra-violet, infra-red, and Rontgen radiations are discussed at 

 some length. The rest of Part III is devoted to photometry, 

 spectrophotometry, the human eye, color vision, lamps, and illu- 

 mination. The titles of the chapters of Part IV are : " the Nature 

 of Light, the Electromagnetic Theoiy of Light, Reflection and 

 Refraction, the Theory of Dispersion, Theory of Radiation," and 

 " the Relative Motion of Matter and Ether." With regard to the 

 chapter on the nature of light the author says: — "From the 

 nature of the subject the chapter is a difficult one ; it may be 

 omitted without prejudice to those that follow." 



It is thus evident that the entire field is covered with sufficient 

 thoroughness to give the student an excellent perspective of the 

 subject of light. The author's style is clear and concise and his 

 presentation of the material of Part IV is especially illuminating. 

 On the other hand, the text as a whole seems to be of a more 

 advanced character than can usually be assimilated by a student 

 who has had only one year of physics. At the ends of the chap- 



