1134 Notices respecting New Books. 



the extensive circulation which it certainly merits, the rather high 

 price set on it by the publishers rather than any fault of the 

 author's will be the cause. 



Moderne MagnetiJc. By Felix Atiebbach. Pp. viii+ 304. 

 Leipsig : J. A. Earth, 1921. Price 55 M. 



This book gives a remarkably comprehensive account of magnetism 

 in all its bearings. The properties of magnets and ferromagnetic 

 bodies, and of the various methods employed for measuring the 

 strength of magnetic fluids and the permeability of specimens, are 

 expounded in a clear and logical manner, all practical experimental 

 devices, including Lenard's bismuth spiral, being described, if only 

 in outline. This is the ground covered in more detail in Ewing's 

 well-known book, but much matter which has appeared since the 

 date of that work finds reference here. In addition we have 

 chapters devoted to the effect of mechanical deformation (tension, 

 torsion, and so on) on magnetic properties, to magneto-optics, to 

 recent theories, and to phenomena connected with terrestrial 

 magnetism. The last mentioned contains an all too brief account 

 of Birkeland's and Stormer's beautiful work on the aurora, with a 

 few of their pictures. The modern electron theories of magnetism 

 of Gans, Langevin, and Weiss are My expounded, but no reference 

 is made to the bearing of Bohr's work on the Zeemau effect, 

 Yoigt's theory of the effect, which has had no outstanding 

 success, being given instead. 



It will be seen that a great deal of modern work, which has not 

 yet found its way into the ordinary English text-books, has been 

 compressed into this book. On account of the very wide scope 

 no detailed treatment is possible, and intriguing phenomena, such 

 as those exhibited by the Heusler alloys, are dismissed in a couple 

 of pages. This is inevitable in a book of this size, and is not 

 mentioned as a hostile criticism. Considering the limits which 

 the author has set himself, everything is very clearly treated. 

 The book is written in a pleasant, human, aud picturesque style, 

 with considerably more liveliness than a German scientist usually 

 allows himself. There is an amusing digression on text-books at 

 the beginning of Chapter IX. "We commend this book, and think 

 that many readers of the Philosophical Magazine will find it 

 useful. 



