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BELL SYSTEM TECHNICAL JOURNAL 



mentioned characteristic precludes the use of any but measuring 

 instruments of the highest degree of sensitivity and makes desirable 

 the use of comparatively high humidities, and the second characteristic 



1 2 34 5 67 89 10 n 12 



TIME IN DAYS 



Fig. 3 — A.C. capacitance of SO ft. of twisted pair wire insulated with double serving 



of equal thickness. 



means that the specimen must be tested under exceedingly well 

 controlled relative humidity conditions. Furthermore, the problem 

 is complicated by the polarization effect discussed in the paper by 

 Williams and Murphy, and the fact that this effect varies in magnitude 



