AND MODERN PHYSICS. 209 



and Rubens in rapidly varying fields lead to values 

 which do not -differ greatly from those given by other 

 methods. The theory, however, of these experiments 

 seems open to criticism. 



To attempt anything like a complete account of 

 modern verifications of Maxwell's views and modern 

 developments of his theory is a task beyond our 

 limits, but an account of Maxwell written in 18U5 

 would bo incomplete without a reference to the work 

 of Heinrich Hertz. 



Maxwell told us what the properties of electro- 

 magnetic waves in air must be. Hertz* in 1887 enabled 

 us to measure those properties, and the measurements 

 have verified completely Maxwells views. 



The method of producing electrical oscillations in 

 a conductor had long l>een known. Thomson and Von 

 HelltiholU hud both pointed it out. Schiller had 

 examined .such oscillations in 1874, and had deter- 

 mined the inductive capacity of glass by their means, 

 using oscillations whose period varied from '000050 to 

 000 12 of a second. 



These oscillations were produced by discharging 

 a condenser through a coil of wire having self- 

 induction. If the electrical resistance of the coil be 

 not too great, the charge oscillates backwards and 

 forwards between the plates of the condenser until its 

 energy is dissipated in the heat produced in the wire, 

 and in the electro-magnetic radiations which leave it. 



The period of these oscillations under proper 

 conditions is given by the formula T = 2 * v/C 1 where 



* Hertz's papers have been translated into English by D. E. Jonet, 

 ami are published under the title of Kfatric H'tirr*. 

 X 



