64 Scientific Intelligence. 



ity and the concentration of ions. Interesting curves of the 

 oscillations and aperiodic effects in various forms of cells accom- 

 pany the paper. — Ann. der Physik, No. 14, 1906, pp. 701-755. 



J. T. 



10. Electric Waves. — A paper on this subject forms the last 

 contribution of P. Drude to the Annalen, and, therefore, has a 

 peculiar interest. The conclusions of the paper are as follows : 

 The best systems of wireless telegraphy, in his opinion, must 

 have: 



(1) Magnetic coupling. 



(2) Perfect identity between sender and receiver. 



(3) As a receiver, the ii*on bundle of wires (magnetic detector) 

 must be surrounded by the wire which is connected to the capac- 

 ity.— Ann. der Physik, No. 14, 1906, pp. 832-847. J. t. 



11. Fluorescence and Magnetic Rotation Spectra of Sodium 

 Vapor and their Analysis. — Professor R. W. Wood has dis- 

 covered a remarkable effect of the magnetic field on the radia- 

 tions emitted by sodium vapor when it is stimulated by light of 

 various wave-lengths and light from different sources. He 

 shows that the complex fluorescent spectrum is made up of six 

 or more series of lines, with regular spacings. — Phil. Mag., Nov., 

 1906, pp. 499-524. j. t. 



12. .Radioactive Transformations ; by E. Rutherford. Pp. 

 287. New York, 1906 (Charles Scribner's Sons). — This volume 

 presents in published form the series of eleven lectures delivered 

 in March 1904 in the Silliman Memorial Lecture course at Yale 

 University. 



The subject is treated systematically and critically from the 

 standpoint of the disintegration theory, and as the work of the 

 pen of so eminent an authority in these matters is a valuable 

 contribution to the literature. In a short historical introduction, 

 the theories concerning the electrical nature of matter, the ioniza- 

 tion of gases, the more important properties of radio-active 

 bodies and the various methods of measurement of radio-active 

 quantities are briefly but clearly given. The succession of radio- 

 active changes taking place in thorium are then treated in detail 

 as a typical example of the processes occurring in radio-active 

 substances and the theories advanced for their explanation. The 

 more complex problem of the changes in radium is next con- 

 sidered and the successive transformations taking place in this 

 series are explained and analyzed. This is followed by a chapter 

 on uranium and actinium and the connection between the dif- 

 ferent radio-elements. The production of helium, the radio- 

 activity of the earth, the properties of the a rays and the 

 radio-active processes in general are then discussed in separate 

 chapters. It is significant of the rapid increase in our knowledge 

 on the subject of radio-activity that the author has thought it 

 desirable to incorporate the results of many important investiga- 

 tions which have been made since the lectures were delivered. 



The book is most readable and suggestive throughout and 



