HERTZ, THE DISCOVERER OF ELECTRIC WAVES 333 



which this very question might be studied." But, as he said after- 

 wards in speaking of Hertz's work, "I did not see any feasible way of 

 detecting the induced resonance: I did not anticipate that it could 

 produce sparks." Concerning this contrivance the following interest- 

 ing remarks were made by its author in his Heidelberg lecture above 

 referred to: "The method had to be found by experience, for no amount 

 of thought could well have enabled one to predict that it would work 

 satisfactorily. For the sparks are microscopically short, scarcely a 

 hundredth of a millimeter long; they only last about a millionth of a 

 second. It seems absurd and almost impossible that they should be 

 visible; but in a perfectly darkened room they are visible to an eye 

 which has been rested in the dark. Upon this thin thread hangs the 

 success of our undertaking." Multum in parvo, truly! 



After a series of preliminary experiments, in which he studied the 

 various induction effects, including the phenomenon of resonance, and 

 demonstrated waves on wires (an earlier, but overlooked, discovery of 

 von Bezold, in 1870), and also solved the problem of the Berlin 

 Academy— "to establish experimentally any relation between electro- 

 magnetic forces and the dielectric polarization of insulators"- — he was 

 fully convinced that the disturbance was propagated through space, 

 independently of wires, with a finite velocity and in the form of waves, 

 in accordance with Maxwell's prediction. His conclusion was then 

 definitely and convincingly proved by making use of the well-known 

 method of reflection and interference to produce standing waves, and 

 noting the position of the nodes and antinodes. These epochal experi- 

 ments were described in a paper entitled "Electromagnetic Waves in 

 Air and Their Reflection," published in May, 1888. But he did not 

 stop there, and in these and succeeding investigations he showed that 

 electric waves are reflected from plane and curved metal surfaces in 

 accordance with the same laws as light waves; that they are refracted 

 in passing thorugh prisms of pitch, parafhn, and other dielectrics; and 

 that they are polarized by a grating of parallel wires, and hence are 

 transverse waves. From actual measurements of their wave-length 

 and computations of their frequency (from the constants of his oscil- 

 lator), he calculated their velocity and found that it was the same as 

 the velocity of light. As summarized by Hertz himself, "The object 

 of these experiments was to test the fundamental hypotheses of the 

 Faraday- Maxwell theory, and the result of the experiments is to con- 

 firm the fundamental hypotheses of the theory." The old action-at- 

 a-distance philosophy had come to an end. 



The importance of Hertz's contributions to this great subject re- 

 ceived instant and enthusiastic recognition, and his experiments were 



