422 BELL SYSTEM TECHNICAL JOURNAL 



dimensions as lo be in resonance with his high frequency oscillator. It 

 was by this careful exploration that Hertz demonstrated, for the first 

 time, the existence of electromagnetic waves in space. In the first of his 

 series of papers describing these experiments, "On Very Rapid Electric 

 Oscillations," published in 1887, he devotes one section to a discussion of 

 "Resonance Phenomena." An extract from this will show how he was 

 thinking: 



"But it seemed lo me that the e.xistence of such oscillations might be proved by 

 showing if jwssible symphonic relations between the mutually reacting circuits. 

 According to the principle of resonance, a regularly alternating current must 

 (other things being similar) act with much stronger inductive effect upon a circuit 

 having the same period of oscillation than upon one of only slightly different period. 

 If, therefore, we allow two circuits, which may be assumed to have approximately 

 the same period of vibration, to react on one another, and if we vary continuously 

 the capacity or coefficient of self-induction of one of them, the resonance should 

 show that for certain values of these quantities the induction is perceptibly 

 stronger than for neighbouring values on either side."'^ 



A series of experiments along these lines demonstrated the effect con- 

 clusively. In the secondary circuit the length of spark that could be 

 obtained across the adjustable gap increased to a maximum when the two 

 circuits were in tune. The first electrical resonance curve ever published is 

 given in the above mentioned paper,^- a relation between the length of wire 

 in the detecting loop and the greatest length of spark obtainable for each 

 length of wire, all other conditions remaining unchanged. The curve 

 show^s the familiar sharp peak at the point of resonance. In all his succeed- 

 ing researches on electric waves Hertz used this simple tuned circuit as a 

 detector. It was the forerunner of the resonance type of wave-meter to be 

 used later in the yet unborn art of radio. 



Among the prominent British physicists Oliver Lodge at this time was also 

 experimenting with electrical resonance and writing and lecturing about it. 

 He had from the first taken a keen interest in the work of Hertz and in fact 

 came close to anticipating Hertz in the discovery of electric waves through 

 his notable work on lightning conductors. In a brief article published in 

 1890 he described a method, which he had used a year before in a lecture, of 

 displaying the spark producing power of electric radiation by tuning the 

 circuit of one Leyden jar to that of another containing a spark gap and 

 excited in the usual way.^^ When the secondary circuit was in resonance 

 with the first its Leyden jar would "overflow." But Lodge objected to the 

 use of the term "resonance" and preferred the term "syntony"; "the name 

 'resonance' is too suggestive of some acoustic reverberation phenomenon 

 to be very expressive," he maintained.^'' Although he and some of the other 

 English writers continued to say "syntony" and "syntonic", this termi- 

 nology did not permanently stick. 



