RESIDUAL CHARGE OE CONDENSERS. 235 



of homogeneity does not seem to be the sole cause of the phe- 

 nomenon, and experiment shows that the existence of residual 

 charges must in most cases be ascribed to a kind of elastic de- 

 formation which is caused by the polarization of the dielectric. 

 It must be observed that all actions, such as repeated shocks, 

 vibrations, sudden variations of temperature in opposite directions, 

 which facilitate the return to the normal state, of a body which 

 has undergone any permanent elastic deformation, also facilitate 

 the appearance of residual charges and their return to the natural 

 state. 



The propagation of heat gives rise to no phenomenon which 

 could be compared to the residual charge of dielectrics, and in this 

 respect the analogy, which in so many respects is so close between 

 the two orders of phenomena, ceases to hold. 



