206 Specific Inductive Capacity of Electrolytes. 



would equal ?i 2 . The electrical behaviour of glass has been 

 compared with the mechanical behaviour of pitch, which is 

 elastic to forces acting through short periods such as those of 

 sound, but viscous to forces of long periods. If we accept 

 this very reasonable explanation for glass, we at once extend 

 it to the large class of liquids of various degrees of insulating 

 power called dielectrics, and for which K is greater than n 2 , 

 and also to that group of alcohols and their derivatives which 

 Tereschin * has investigated, and for which the values of K 

 vary from 2 to 32. It is but another step to water with 

 a value of K in the neighbourhood of 75. One can easily 

 imagine that for electrical stresses of a period 10~ 15 sec. 

 K can equal n 2 ; that is, be less than 2, and possess a tempe- 

 rature-coefficient equal to that of n 2 . 



That a thing is conceivable and that it is demonstrated are 

 not equivalent. Nevertheless the behaviour of water, alcohol, 

 and other conducting liquids, as cited in the foregoing pages 

 and as given by other observers, seems to me to afford very 

 strong reasons for attributing to these electrolytes a genuine 

 specific inductive capacity. 



This investigation was carried on under the general direction 

 of Prof. A. L. Kimball, of the Johns Hopkins University. 

 The experiments were made at the Physical Laboratory of the 

 University of Wisconsin ; and I take pleasure in acknow- 

 ledging my obligation to Prof. J. E. Davies, who generously 

 placed at my disposal the utmost resources of his laboratory, 

 and who furnished me with the beautiful rotating commutator 

 which was constructed from my design in the University 

 machine-shops. 



Johns Hopkins University, 



Baltimore, Dec. 20, 1890. 



Note, added January 14, 1891. — It is well known that a 

 dielectric in a non-uniform electric field tends to move toward 

 regions where the force is greater or less (like magnetic and 

 diamagnetic bodies in a magnetic field), according as the 

 specific inductive capacity of the body is greater or less than 

 that of the medium in which it is placed. For example, if 

 the body is glass (K = 6 to 10), it will tend to move toward 

 places where the force is greater in such media as air and 

 other gases and in turpentine, oils, and most liquid dielectrics. 

 But in alcohol, water, and other liquids having larger specific 

 inductive capacities we should expect it to move in the 

 opposite direction. 



* Wied. Ann. Bd. xxxvi. S. 792 (1889). 



