Velocity of Electric Waves in Air. 



117 



In the experiment about to be described, a new method was 

 employed by which the direct determination of the period of 

 the oscillator was made. The oscillator and resonator were 

 tuned by using a special form of self-induction and capacity 

 and balancing them. The resonators used by Hertz and the 

 other physicists to whom reference above has been made, were 

 simple loops of copper wire which acted as the self-induction, 

 while the capacity was that of two small metal spheres. The 

 oscillators had very large capacities in comparison with those 

 of the resonators. 



In our experiment the form and size of oscillator and reso» 

 nator, as also the dimensions of their self-inductions and 

 capacities, are identical. The resonator here used is a specially 

 devised coherer. Many attempts of late have been made to 

 employ the coherer successfully to measure electric waves. The 

 results have generally been to stamp the coherer as an instru- 

 ment too capricious for such work. In this connexion may 

 be mentioned the work of Professor Murani *. He used a 

 Marconi coherer and a galvanometer. The readings of his 

 galvanometer, as he moved the coherer farther and farther 

 from the reflector, changed; no zero-readings, however, were 

 found, and there was no regular increase and decrease in the 

 readings. The following table is taken from his paper : — 



Distance of coherer 

 in cms. from reflector. 



Deflection of 

 galv.-needle. 



Distance of coherer 

 in cms. from reflector. 



Deflection of 

 galv.-needle. 



2 



120 

 13-4 

 16-2 

 lfi-3 

 16-4 

 155 

 158 

 155 

 158 

 15-5 

 155 

 16-0 

 15 4 



65 



160 

 170 

 165 

 162 

 15 8 

 10-2 

 16-5 

 16-0 

 163 

 164 

 172 

 17 1 



5 



70 



10 



75 



15 



80 



20 



25 



90 



100 



30 



no 



35 



120 



40 



45 



130 



140 



150 



50 



55 



200 



60 







His results were submitted to Professor A. Righi, who, 

 with Professor Murani, concluded that this coherer was 

 unsuitable for the measurement of stationary electric waves 



* Stuiio dull Ondc stazionarie de Hertz col Mezzo di ui C>h°rer del 

 Prof. O. Murani del R. Istituto Lombardo. Milano, 18)8. 



