The Followers of Maxwell. 357 



After his attempt to justify the Maxwellian equations on 

 theoretical grounds, Hertz turned his attention to the possibility 

 of verifying them by direct experiment. His interest in the 

 matter had first been aroused some years previously, when the 

 Berlin Academy proposed as a prize subject " To establish 

 experimentally a relation between electromagnetic actions and 

 the polarization of dielectrics." Helmholtz suggested to Hertz 

 that he should attempt the solution ; but at the time he saw 

 no way of bringing phenomena of this kind within the limits of 

 observation. From this time forward, however, the idea of electric 

 oscillations was continually present to his mind ; and in the 

 spring of 1886 he noticed an effect* which formed the starting- 

 point of his later researches. When an open circuit was formed 

 of a piece of copper wire, bent into the form of a rectangle, 

 so that the ends of the wire were separated only by a short air- 

 gap, and when this open circuit was connected by a wire with 

 any point of a circuit through which the spark -discharge of an 

 induction-coil was taking place, it was found that a spark 

 passed in the air-gap of the open circuit. This was explained 

 by supposing that the change of potential, which is propagated 

 along the connecting wire from the induction-coil, reaches one 

 end of the open circuit before it reaches the other, so that a 

 spark passes between them; and the phenomenon therefore 

 was regarded as indicating a finite velocity of propagation of 

 electric potential along wires.! 



* Ann. d. Phys. xxxi (1887), p. 421. Hertz's Electric Waves, translated by 

 D. E. Jones, p. 29. 



t Unknown to Hertz, the transmission of electric waves along wires had been 

 observed in 1870 by Wilhelm von Bezold, Miinchen Sitzungsbericlite, i (1870), 

 p. 113 ; Phil. Mag. xl (1870), p. 42. * If," he wrote at the conclusion of a series 

 of experiments, "electrical waves be sent into a wire insulated at the end, they 

 will be reflected at that end. The phenomena which accompany this process in 

 alternating discharges appear to owe their origin to the interference of the 

 advancing and reflected waves," and, "an electric discharge travels with the 

 atne rapidity in wires of equal length, without reference to the materials of 

 which these wires are made." 



The subject was investigated by 0. J. Lodge and A. P. Chattock at almost the 

 same time as Hertz's experiments were being carried out: mention was made of 

 their researches at the meeting of the British Association in 1888. 



