﻿400 



Mr. Rollo Appleyard on Dielectrics. 



The curves practically overlap. The insulation falls some- 

 what with the increase of voltage, but recovers its original 

 value as the cycle is completed. There was no observable 

 " electrification"; the first and second minute readings were 

 in each case identical. 



The next sheet of celluloid tested was 6 mils in thickness. 

 Here again there was no sign of " electrification," though 

 there was a distinct diminution of insulation with voltage. 

 This sheet broke down at 1200 volts ; there is nothing in the 

 curve to indicate that such a rupture was about to take place. 

 These results are given in Table III. 





Table III. 







Resistance 



Volts increasing. 





in megohms. 



150 





30-0 



300 





29-6 



450 





29-2 



600 





28-4 



750 





27-7 



900 





26-8 



1050 





26-0 



1200 





Broke down 



A third sheet, cut from the same specimen as the last, was 

 then tested through a cycle from 150 to 1050 volts ; it 

 showed practically no hysteresis and no rt electrification," the 

 return values being simply reproductions of the rising ones. 

 There is the same drop in insulation with voltage as in the 

 previous tests, as shown by Table IV. 



Table IV. 



Volts increasing. 



Volts diminishing. 



Volts. 



Resistance 

 in megohms. 



Volts. 



Resistance 

 in megohms. 



150 

 300 

 450 

 600 

 750 

 900 

 1050 



26-34 

 25-56 

 24-93 

 24-15 

 23-51 

 22-72 

 21-89 



900 

 750 

 600 

 450 

 300 

 150 



22-72 

 23-48 

 24-15 

 24-93 

 25-68 

 26-52 



