Mabch 9, 1906.] 



SCIENCE. 



385 



frequently hear of its bearing good fruit 

 in campaigns.. In our society, either as 

 officers or on the advisory boards, are many 

 men of broad influence in the country. 

 Among these the earliest to go into the 

 movement, inspired by the entomologist 

 before referred to, were Matheson, Kerr, 

 Miller, Hoyt, Cravath, Rand and Wetmore 

 — business men of largest affairs. 



We have got such men together, with 

 many others known over the world, into a 

 society, which, according to its constitu- 

 tion, seeks 'to unite in a general body, per- 

 sons believing in the various great evils 

 resulting from the unrestrained breeding 

 of mosquitoes in civilized sections, and in 

 the practicability of their extermination 

 therefrom, by private and public system- 

 atic operations.' 



For these worthy objects we ask your 

 active cooperation with us and. in closing 

 thank you for your attention. 

 (To he continued.) 



SCIENTIFIC BOOKS. 

 The Analytical Theory of Light. By James 

 Walker. New York, The Maemillan Com- 

 pany. Pp. XV 4- 412. $5 net. 

 The Electromagnetic Theory of Light. By 

 Charles Emerson Curry. New York, The 

 Maemillan Company. Part I. Pp. xv + 

 400. 



Walker's ' Analytical Theory of Light ' is, 

 perhaps, the most complete treatment of the 

 subject so far attempted from the standpoint 

 of the general wave theory, without any special 

 assumption as to the character of the waves 

 or the nature of the transmitting medium. 

 With this restriction in mind, it is not sur- 

 prising to find relatively much more space 

 given to the older and more worked-over parts 

 of the subject, such as interference, diffrac- 

 tion, isotropic and crystalline reflection and 

 refraction and the interference of polarized 

 light, as contrasted with absorption, dispersion 

 and magneto-optics, those portions which at 

 present seem more fruitful of interesting and 

 important results. While the book is built 



on a rigorous analytical framework, never- 

 theless frequent comparison with experimental 

 facts, and more sparing application of theory 

 to instrumental methods keep the reader in 

 touch with the physical side of the subject — 

 to which end numerous references to the 

 literature of the various special fields also 

 assist. The book is written in a clear and 

 attractive style, and its value as a reference 

 work is increased by an index as well as by 

 appendices dealing with the properties of 

 Bessel's, Struve's and Lommel's functions. 



It is in one sense hardly fair to criticize a 

 book because it is too exactly what its author 

 intended it to be; at least one should, while 

 questioning his judgment, commend his 

 pertinacity of purpose. This applies to the 

 second of the above books, Part I. of Curry's 

 ' Electromagnetic Theory of Light,' in which, 

 as is stated in the preface, ' empirical facts ' 

 are referred to ' only where a comparison with 

 theoretical results seemed of interest.' One 

 must regret that so few cases ' seemed of in- 

 terest ' — for the result is a book unnecessarily 

 abstract, which, while entirely modern in treat- 

 ment, and sufiiciently cognizant of recent 

 theoretical discussions, is out of touch with the 

 experimental side of the science. While this 

 general method of treatment has been most 

 successfully applied to the more finished sci- 

 ence of mechanics, it hardly seems at present 

 the best for the less developed field of optics. 

 This point of view is, perhaps, responsible for 

 one or two rather amusing misstatements, as 

 for instance (p. 13) that the varying sensi- 

 bility of the eye to different wave-lengths, fol- 

 lows because the usual expression for the in- 

 tensity of a ray of light 



\ ^^^/ 



contains the wave-length. 



The treatment is throughout based on the 

 electro-magnetic theory of Maxwell, but a very 

 considerable amount of space is given to the 

 discussion of ' primary ' and ' secondary ' 

 waves, the exact definition of which and their 

 special treatment is due to the author. Aside 

 from this the ground covered is about the 

 same as in the earlier chapters of Walker's 

 treatise, with, however, emphasis laid on dif- 



