600 Notices respecting JVew Books. 



Rim section: in a radial direction = 7 cm. 

 in an axial direction = 4 cm. 

 Volume of rim = ttx4x [(51/2) 2 -(37/2) 2 ] 



= 3-84 xlO 3 cubic cm. 

 Weight of rim (taking specific gravity of porcelain at 2'4). 



= 9'2xl0 3 grm. 

 Moment of inertia of disk about principal axis 



= 4-26 x 10 6 grm. cm. 2 . 



LXV. Notices respecting New Books. 



Oliver Heaviside. Electromagnetic Theory. Volume III. London : 

 ' The Electrician ' Printing & Pub. Co., Ltd. Pp. ix + 519. 



HPHIS is the third Volume, impatiently expected by all true 

 -■- admirers of Oliver Heaviside, of his unparalleled work on 

 Electromagnetic Theory. The present volume has been delayed 

 by "not favourable circumstances" for eight years (1904-12). 

 Still it was published as long ago as September 1912, and the 

 reviewer profoundly regrets that, again through " circumstances/' 

 the present Notice has been delayed over four years. But the 

 consolation is that the reviewed volume — as, in fact, every work of 

 Heaviside — is never too old. It has the freshness and the life 

 of originality, and is, both as regards contents and form, stimu- 

 lating beyond saying. In a very short Preface the author explains 

 that he has " excluded parts of the third volume and included 

 parts of the fourth." This confession is regrettable, inasmuch as 

 it seems to imply that the plan of publishing a fourth volume has, 

 for the time at least, been abandoned. 

 The present volume is inscribed : 



IN MEMORY OF 



G-eorge Francis EitzGerald, E.E.S. 

 " We needs must love the highest when we " know him. 



A large portion of the substance has been reprinted from 

 * The Electrician ' and ' Nature,' one section from ' Ency. Brit.' 

 10th Ed., and another from Perry's Book, 1901 ; but many pages 

 of the volume are now first published. The whole volume consists 

 of : Chapter IX., treating oiWavesfrom Moving Sources, Appendices 

 J and K, and Chapter X., entitled Waves in the Ether, but con- 

 taining such (non-ethereal, but equally interesting) matter as 

 " The Teaching of Mathematics " and " Scientific Limitations on 

 Human Knowledge," and, on the other hand, " Eotation of a 

 Eigid Body " and " Deep Water Waves." In short, it is what 

 one calls Miscellanea. The better so for the intelligent reader. 



