Electrical Oscillations in Air. 323 



It is established then that the periods of vibration of the 

 molecules of solids at their melting-points shoiv very simple 

 harmonic relations. 



It is an interesting speculation in molecular physics as to 

 whether by the analysis of the whole radiation from melting 

 solids with bolometer and spectroscope similar harmonic 

 relations could be found and so demonstrate the communica- 

 tion of impressed vibrations to the sether from the oscillating 

 molecules. A similar study to the above made on organic 

 compounds might yield useful information about the harmonic 

 connexions of the organic radicals. 



Melbourne, July 1890. 



XXXVII. Electrical Oscillations in Air. 

 By John Trowbkidgb and W. C. Sabine*. 



THE experiments of Hertz on electrical waves have opened 

 a wide field for investigations in electromagnetism. 

 The qualitative results of Henry and of Feddersen have been 

 expressed in a quantitative manner by Sir William Thomson. 

 Hertz, collecting together the results of previous observers, 

 and reasoning upon the factors in the formula of Sir W. 

 Thomson, — which expresses a relation between the capacity 

 of a Leyden jar and the self-induction of the circuit through 

 which this jar is discharged, — has detected wave-motion with 

 its nodal points and ventral segments, on a wire over which 

 electrical oscillations take place. 



Hertz has also pointed out that the experimental results 

 confirm Maxwell's theory, that light and heat are electro- 

 magnetic phenomena, and that all energy comes to us from 

 the sun in electrical pulsations. 



There can be no question of the phenomena of so-called 

 resonance discovered by Hertz. Roughly speaking, the 

 results obtained by Hertz's resonators satisfy the formula 



o 



t= — vLC ; in which t is the period of the electrical oscilla- 



v 



tions, L is the inductance of the circuit, and C is the capacity 

 of the jar, or that of the terminals between which the elec- 

 trical discharge takes place. 



Professor J . J. Thomson has based a method of measuring 

 the capacities of dielectrics upon this formula and upon 

 Hertz's work f. 



* From the Proceedings of the American Academy of Arts and 

 Sciences. Advance proof communicated by the Authors, 

 t Proceedings of the Eoyal Society. June 20, 1889. 



