964 



SCIENCE 



[N. S. Vol. XXV. No. 691 



chloride and copper bromide in methyl and 

 ethyl alcohol and in acetone are also studied. 

 Photographic records showing the absorption 

 bands in the different solutions are presented. 

 These photographs show admirably how the 

 absorption bands gradually change as the 

 various dehydrating agents mentioned are 

 added to the solutions. In the disciission of 

 the results the dilficulties met in interpreting 

 spectroscopic observations of this kind are 

 clearly set forth. In fact the second part of 

 the monograph is more carefully and judi- 

 ciously written than the first part, the latter 

 containing practically no reference to the ex- 

 perimental work of others, whereas in the 

 second part the work and opinions of other 

 investigators receive due consideration. At- 

 tempts to deduce the approximate quantitative 

 composition of the hydrates in solution from 

 the study of the absorption spectra are, of 

 course, not made, for such observations do not 

 lend themselves for that purpose. It is simply 

 claimed that the results bear out Jones's ideas 

 of hydrates in sokition in a satisfactory 

 manner. 



Louis Kahlenberg 

 Univeksitt of Wisconsin, 

 May 10, 1907 



Electrons or the Nature and Properties of 



Negative Electricity. By Sib Oliver Lodge. 



London, George Bell and Sons. 1906. Pp. 



xvi + 230. 



Up to the time of the publication of Max- 

 well's ' Treatise on Electricity and Magnet- 

 ism ' in 18Y3, in which the ideas of Faraday 

 were subjected to mathematical analysis, and 

 greatly extended, the preponderating role 

 which the luminiferous ether plays in electro- 

 dynamic phenomena had been almost entirely 

 overlooked by theoretical physicists. Atten- 

 tion had been concentrated upon electrical 

 charges and currents, and the influence of 

 the medium which transmits electric and mag- 

 netic forces was quite neglected. The steady 

 progress of Maxwell's theory, its evident 

 superiority to its older rivals, and its final 

 triumphant verification by Hertz, naturally 

 caused the pendulum to swing to the other 

 extreme; so that in the early nineties students 



of physics learned much of tubes of force and 

 ethereal displacement, but had little to do 

 with electric charge, except as a rather old- 

 fashioned idea still useful for certain pur- 

 poses, but really only a short name for a cer- 

 tain mathematical function of the ethereal 

 displacement. 



Time, however, has wrought its revenges. 

 When Maxwell's theory was applied to the 

 finer details of the electrical and optical be- 

 havior of matter, especially of moving matter, 

 it was found necessary to reintroduce the 

 definite conception of electric charge in very 

 concrete form; its atomic structure was recog- 

 nized, and the name ' electron ' was given to 

 the atom of electric charge. These theoretical 

 conclusions of Lorentz and Larmor have been 

 strikingly confirmed by a great number of ex- 

 perimental results in widely different fields of 

 investigation. The discovery of the Zeeman 

 effect, the investigation of the nature of 

 cathode rays and of the ionization of gases by 

 J. J. Thomson and his followers, the phe- 

 nomena of radioactivity and many other 

 facts new and old find their natural explana- 

 tion in terms of the electron theory. Indeed 

 we have some ground for anticipating a much 

 wider extension of the theory; it is not im- 

 possible that we may come to believe that all 

 matter is made up of electrons, which will 

 thus form the raw material out of which the 

 material universe is constructed. 



In the book under review. Sir Oliver Lodge 

 has given a simple and lucid account of this 

 theory, of its triumphs and difficulties, and 

 the possibilities of its future development. 

 He tells us that the book " is intended for the 

 student of general physics, and in places for 

 specialists, but most of it may be taken as an 

 exposition of a subject of inevitable interest 

 to all educated men." It is in fact not quite 

 a ' popular ' exposition of science in the ordi- 

 nary sense, and one will look in vain for the 

 exaggerations and over-statements which are 

 too often characteristic of such works. It 

 appeals rather to the discriminating amateur 

 of scientific knowledge who has some knowl- 

 edge of electricity and who will not be hope- 

 lessly frightened or repelled by an occasional 

 simple algebraic or trigonometrical expression. 



