Notices respecting JSew Boohs. 



601 



In Chapter IX. we heave, first of all, a number of remarkably 

 elegant solutions of problems concerning the " waves from sources," 

 electrified points, lines, strips, and planes travelling at any speed. 

 Then (pp. 43-61) there is a very natural digression into the 

 "Drag of Matter upon Ether" and associated questions. The 

 author tries several modifications of the " circuital equations " and 

 discusses also Lorentz's equations. Here he exclaims : " To find 

 Lorentz. After profound research I succeeded in discovering. . . . 

 Lorentz's Versuch einer Theorie, etc. This important application 

 of Maxwell's theory. . . .ought to have been done in English at 

 once to save repetitional labour. Though sad, it is a fact that few 

 Britons have any linguistic talent .... Foreigners^ on the other 

 hand, seem to be gifted linguists quite naturally." Heaviside 

 forgets that they also have to learn the foreign languages, English 

 included, and that it is not an easy task in many cases. Then 

 the author proceeds humorously : " Very well ; I would say, let 

 them give us poor islanders the benefit of their skill by doing 

 all their best work into English. And why not make English the 

 international scientific language? It would be all the same to 

 the foreigners." This presupposes the absence, in all other 

 nations, of any attachment to their traditional means of expression. 

 It is easier to translate such classical things as Lorentz's 'Yersuch ' 

 into English — and, as we know, an English translation of this by 

 no means voluminous work is being prepared by Dr. Andrade. 

 " On examination," Heaviside finds " that Lorentz's equations do 

 lead to the Eresnel wave-speed," a property universally known 

 these twenty years. Notwithstanding this, many readers will be 

 glad to see (pp. 53-56) the way in which Fresnel's coefficient does 

 follow from Lorentz's equations. The next section is dedicated to 

 criticism of Larmor's equations, and contains some just remarks 

 on the lack of clearness in 'Ether and Matter.' The next sections 

 are dedicated to the theory of moving electrified cones and the 

 force acting upon them and upon an electrified line, of a trans- 

 versely moving electrified line segment, and of moving electrified 

 hyperboloids. Eurther, the waves sent out from a growing plane 

 source of induction and from a plane strip suddenly started are 

 investigated. The problem of electrification moving along a 

 straight line gives the author a good opportunity to develop his 

 valuable ideas on operational solutions and on their algebrization. 

 Here also a very interesting construction of simpl} r periodic wave 

 trains from certain electronic steady solutions is given (§ 4S6). 

 §§ 488-500 treat chiefly of the interesting problems of sudden 

 motions of an electron in connexion with Eontgen rays, and 

 contain illuminating remarks on the peculiarities of the speed of 

 light and an important investigation of the energy wasted in the 

 pulse from a jerked electron and the energy left behind. The 

 chapter closes with an investigation of the motion of a charged 

 spheroid along its axis. 



The short Appendix J contains a note on the size and inertia of 

 electrons, now of historical interest only. 



