236 BELL SYSTEM TECHNICAL JOURNAL 



did not involve any special attention to the time of application of 

 voltage. 



Evershed's explanation of decreased insulation resistance with in- 

 creased voltage involves the assumption that much of the water 

 contained in insulations is originally in the form of isolated pools and 

 therefore of no conductive effect at the instant of application of 

 voltage. In support of his theory of "dormant" water, he lays great 

 stress upon his observation that the volume of water present in the 

 insulating materials is far in excess of that which would be required to 

 furnish the observed conductivity if the water were in the form of 

 continuous filaments of uniform cross section. This argument seems 

 impressive and conforms to our own ideas of the distribution of water 

 in textiles. However, according to Evershed, this pool water is 

 electrokinetically spread out into conducting films under electric 

 stress, thus accounting for decreased resistance with increased voltage. 

 A tendency to such movement of water cannot be denied. But it is 

 difficult to harmonize Evershed's conception of electroendosmotic 

 movement of water as the predominating phenomenon with all the 

 facts regarding textiles with which we have had experience; for 

 example, with the fact that the Evershed effect is greatest when the 

 electrolyte content of the textile is high. Electroendosmose in systems 

 designed for its ready detection usually diminishes with increasing 

 electrolyte content except when the concentrations are very small. ^^ 

 Further a decrease of resistance with increase of voltage has been 

 noted in other systems in which electrolysis is unquestionably in- 

 volved and in which electrokinetic redistribution of water seems 

 improbable. 



Though sufficient support for an alternative cannot be furnished at 

 present, electrokinesis does not constitute the sole possible explanation 

 of the Evershed effect. The analogy between the moist fiber and an 

 electrolytic cell conforms to a number of other corollary facts about the 

 Evershed effect which are discussed in a more specialized paper by 

 one of the authors.^'' The various properties which have been dis- 

 cussed are in agreement with the view that the cardinal principle of 

 conduction in textiles is the electrolysis of aqueous solutions. 



Distinctive Characteristics of Each Fiber Species 



The several kinds of fibers exhibit a number of curious contrasts 

 in the relation of electrical behavior to hygroscopic properties, some 

 of which at first glance appear contradictory. For convenience in dis- 



16 Powis, Frank, Zeit. Physik. Chem. 89, 91, 1914 and Burton, E. F., Coll. Symp., 

 Monograph IV, 132, 1926. 



I 



