grover: paraffined paper condensers 279 



paper condensers here studied, in no case gave values less than 

 6', and in the case of the poorer condensers the phase difference 

 ranged from 1° to the enormous value of 22°. It was found that 

 in the case of some telephone condensers, made by rolling up 

 together long strips of tin foil and paraffined paper, the energy 

 loss, in the resistance of the tin foil, amounted to considerably 

 more than the loss in the dielectric. (This disadvantage may 

 be avoided by making connection to the tin foil at several points 

 along its length). 



4. The phase difference generally increases with increasing 

 temperatures; and in those condensers with large phase difference, 

 the rate of increase becomes rapidly larger with rising tempera- 

 ture. 



5. The phase difference, when corrected for the resistance of 

 the plates and leads, decreases with increasing frequency, at first 

 rapidly and then more slowly. The rate of change is greatest, 

 at all frequencies, in the case of condensers with large phase dif- 

 ference. 



6. The capacity of a paper condenser varies so considerably 

 with the conditions under which it is used, that such a condenser 

 should not be emploj^ed in work where a knowledge of the capa- 

 city is requisite, except where a previous study of the condenser 

 has shown that it may so be used. 



In the latter half of the paper, the absorption theories of Max- 

 well, 2 Houllevigue, 3 Pellat, 4 von Schweidler 5 and Hopkinson 6 

 are considered for a sinusoidal wave of electromotive force, and 

 the formulas for the capacity and phase difference, as functions 

 of the frequency, are compared with the observed results. The 

 theory of von Schweidler (which is a modification of the Pellat 

 theory and its mathematical equivalent, that of Hopkinson) as- 

 sumes that the absorption in a dielectric is due to the presence 

 of a periodically damped ions and the capacity and phase differ- 



2 Elect, and Magnet., I, § 330. 



3 Jour, de Phys., 6: 113. 1897. 



4 Ann. de Chim. et Phys. 18: 150. 1899. 



5 Ann. der Phys., 24: 787. 1907. 



6 Phil. Trans., 167: 599. 1877. 







