Potential along a Wire transmitting Electric Waves. 341 



through the origin. The ordinate B'S of this line, corre- 

 sponding to the 40-cm. oscillator, has a length or approxi- 

 mately 103 cms. Thus if the principle of direct proportionality, 



Fig. 12. 



stated by Poincare, held without limit to its application, the 

 arrangement of the wire as in the experiments, should be 

 equivalent to adding 44 cms. to the quarter- wave-length of 

 each of the three larger oscillators. On the other hand, the 

 fact that varying the length of the wire from 3 m. to S'6 m. 

 had no effect on the position of the minimum, seems to show 

 that the wire did not act in the manner referred to. In 

 other words, the quarter-wave-lengths given are proper to 

 the oscillators. 



Experiments with the first and second Hertzian oscillators 

 referred to above, gave the following values for the quarter- 

 wave-length : — 



For 40-cm. plates, straight connexion 70 cms.,.. 154*4 cms. 

 30 „ spheres, „ ,, ,, ... 153*9 „ 



These are practically identical. 



For all wires of 3 metres and upwards in length there is 

 a well-defined minimum between 10 and 15 cms. from the end 

 next the oscillator. In figs. 9, 10 (PL VII.) is shown a portion 

 of each curve near the oscillator in continuous line, and also 

 in broken line. In this neighbourhood the oscillator exerted 

 a strong action directly on the detector, In order to allow 

 for this, readings were first taken as usual (shown by con- 

 tinuous line) ; then the wire was removed and readings 

 taken at exactly the same points. These latter were then 

 subtracted from the former, and the broken line shows the 



Phil. Mag. S. 6. Vol. 5. No. 27. March 1903. 2 A 



