96 Prof. J. A. Pollock on the Wave-length of the 



As an example let us take the case o£ a tube of revolution 

 for which y, being equal to y Q over the regular part, becomes 

 y + By between x x and a? 2 « W e have 



Also* 



= 2 0*2 



and 



] 



2 



-^l^W^mh- 



the terms of the first order in &/ disappearing. Thus in the 

 exponent of (35) 



. . . (39) 



of which the right hand member, taken with the positive 

 sign, expresses the retardation of the transmitted wave due 

 to the departure from regularity. 



XIII. The Wave-length of the Electrical Vibration associated 

 with a thin Straight terminated Conductor. By J. A. 

 Pollock, D.Sc, Professor of Physics in the University of 

 Sydney f . 



rilO a first approximation, Abraham { and other writers 

 A conclude from theoretical considerations that the wave- 

 length of the disturbance in free sether due to the gravest 

 electrical vibration on a thin straight terminated conductor 

 is equal to twice the length of the rod. This result is very 

 definitely supported by Lord Rayleigh § in opposition to the 

 calculation of Macdonald ||, which makes the wave-length 

 2*53 times the length of the conductor. 



* ' Theory of Sound,' § 308. 



•J- Communicated by the Author. Read before the Roval Society ot 

 N. S. Wales. 



X Abraham, Ann. der Physik, xlvi. p. 435 (1898). 



§ Rayleigh, Phil. Mag.'viii. p. 105 (1904): Phil. Mag. xxv. p. 1 

 (1913). 



|| Macdonald, ' Electric Waves,' p. Ill (1902). 



