HELMHOLTZ IN BERLIN 



unclosed conductors. He was also of opinion that 

 Wilhelm Weber's supposition that electrical quantities 

 had inertia, like ponderable bodies, was highly improb- 

 able. In 1879, Helmholtz set as a prize research 

 for his students this question of the inertia of 

 electricity, and, in 1880, it was won by Heinrich 

 Hertz, who showed that if it has inertia at all, the 

 latter could only have an influence of the smallest 

 degree conceivable. This was the beginning of the 

 famous work of Hertz, which resulted in the ex- 

 perimental demonstration of Maxwell's magneto- 

 electric waves, and has led to the invention of 

 wireless telegraphy. 



The subject of electrical oscillations was investi- 

 gated by Helmholtz in 1869 and 1871. In 1869 

 he caused his pendulum myograph to close two 

 circuits at short but measurable intervals of time. 

 Oscillations were thus produced in a secondary 

 circuit, the terminals of which were led off to a 

 Leyden jar. The secondary circuit was then broken, 

 and the electrical oscillation was transmitted to the 

 sciatic nerve of a frog-muscle preparation. The 

 number of twitches could thus be recorded. As the 

 time between the completing of the primary and the 

 breaking of the secondary current was increased in 

 successive experiments, alternations in the violence 

 of the twitchings of the muscle were noticed, and 

 in all forty-five minima were observed. 1 In 1871, 



1 Riicker, op. cit., p. 27. 

 215 



