192 Notices respecting New Books. 



elementary principles of spectrum analysis and the construction of 

 the spectroscope, we are introduced to flame-, spark-, and absorption- 

 spectra. The diffraction spectrum and its application to wave- 

 length measurements are next considered, and then follows a 

 chapter on the dark lines produced by absorption. The spectra 

 of the stars and nebulae, the physics of the sun, new stars, double 

 stars, and comets form the subject-matter of the next few chapters. 

 The concave grating and the photography of the spectrum, the 

 relationship betweeu the different lines of a spectrum, and between 

 lines of the spectra of allied elements, band-spectra and spectra 

 of compounds then come in for discussion. The concluding 

 chapters are essentially modern, and deal with the spectrohelio- 

 graph, the electromagnetic theory of light, the Zeeman effect, and 

 the Michelson echelon diffraction-grating. A very complete cata- 

 logue of spectra is given at the end of the book. 



We have noticed a misprint on p. 5, line 7 from top, where 

 " (fx-i)a " should read " (/i — l)a." 



Electro- Chemistry. Part I. General Theory. By R. A. Lehfeldt, 

 D.Sc. Including a Chapter on the Relation of Chemical Con- 

 stitution to Conductivity, by T. S. Moore, B.A., B.Sc. London : 

 Longmans, Green & Co. 1904. Pp. x+ 268. 



This admirable text-book is deserving of the highest praise, and 

 will, we confidently believe, do more towards the advancement of 

 a sound knowledge of electro-chemistry among students of the 

 sister sciences of physics and chemistry than any publication 

 previously issued. Our only fear in reviewing the book is lest 

 our admiration of it should tempt us to the use of expressions 

 which may appear extravagant in their lavish praise. Yet we 

 know of very few books indeed in which such extreme simplicity 

 and charm of exposition are associated with language so severely 

 and scrupulously scientific, so entirely free from that looseness of 

 expression which is by many writers mistaken for simplicity of 

 style. The book is thoroughly modern, in the best sense of the 

 term, and the writer has the rare gift of gauging very accurately 

 the mental attitude of his reader, and, anticipating his difficulties, 

 of dealing with precisely those points which are likely to puzzle 

 him most. The bold and explicit manner in which many knotty 

 points are handled immediately impresses the reader and arouses 

 his interest. 



The work is divided into three chapters, the first of which deals 

 with the mechanism of conduction in electrolytes. The second 

 Chapter, contributed by Mr. Moore, will be found mainly of 

 interest to students of chemistry. The concluding Chapter con- 

 tains a very careful exposition of the theory of electromotive-force. 



We have noticed very few errors, and the revision seems to have 

 been done with great care. On p. 26, line 7 from top, we notice 

 " Eletrolysis " for " Electrolysis ; " and the illustration, fig. 10, 

 does not seem to bear any relation to the description of it given 

 on p. 38. 



