92 Potts — RowlancVs New Method. 



the particles of the dielectric, produced by the electric force 

 between the plates of the condenser. Rowland and Nichols* 

 have shown that certain homogeneous crystals show no electric 

 absorption. H. Hertzf has shown that pure benzine possesses 

 no electric absorption, while impure does4 The great sensi- 

 tiveness of this phenomenon to change of temperature has been 

 noted. The energy loss in condensers due to it has also been 

 studied.§ 



Theory of Electric Absorption. 



The theory of electric absorption has been developed by 

 ClausiusJ Riemann,!" Maxwell** and Rowland. ft The fol- 

 lowing development is that of Maxwell applied by Prof. Row- 

 land to the case of a dielectric acted upon by an e m.f. vary- 

 ing harmonically. 



A dielectric such as paraffin paper is made of a substance of 

 a certain dielectric capacity and specific resistance having 

 imbedded in it particles of a different dielectric capacity and 

 different specific resistance. Now we can very closely approx- 

 imate to this case by considering a plane plate condenser, in 

 which the dielectric is made up of a number of layers of dif- 

 ferent substances. An ordinary condenser is merely a great 

 number of very small condensers like this, joined in multiple. 



The theory of electric absorption as extended by Prof. Row- 

 land shows that a condenser possessing electric absorption 

 •should act as a capacity in series with a certain resistance. 

 The value of each depends on the period of the current. If 

 b v b 2 , etc., are constants and T the period of the current, the 

 resistance is of the form 



R=& i T 2 -&/T+& 3 T 6 , etc. 



and if a t , <2 2 , etc., are constants the capacity is of the form 



-=a-a„T" + cLT\ etc 

 c 



General Theory. — The arrangement adopted is essentially a 

 Wheatstone bridge, in which the fixed coils of an electro-dyna- 

 mometer were placed in one arm of the bridge and the hang- 



* Phil. Mag., p. 414, 1881. 



fWied. Annalen, p. 281, 1883. 



i Phil. Trans., p. 599, 167; Proc. Roy. Soc, p. 468, 1875. 



§ Physical Review, 1899, p. 79. 



|| Theorie Mechanique de la Chaleur ; deuxieme partie. 



■ff Riemann, Mathematische Werke, p. 48. 



** Electr. and Mag., vol. i, p. 452. ff This Journal, Dec. 1897, p. 429. 



