Electrical Conductivity oj Mica in Intense Fields. 123 



be ascribed. It is possible that these fluctuations might, on 

 the average, tend to increase the value obtained. The- 

 readings marked (a) were obtained after the condenser had 

 been charged for 5 minutes ; it will be seen that, at this 

 pressure, there is no evidence of any increase in either the 

 dielectric constant or the conduction current with time. 



V. 



Q. 



h. 



X. 



C. 



C. 



D. 



847 



0374 



8-33 



0-49 









757 



0-338 



8-42 



0-45 









10(50 



0-478 



8-50 



0-61 









1210 



0-574 



8-50 



070 









1428 



0-650 



858 



0-83 









1591 



0-726 



8-61 



092 



001 



001 



000 



(a) 1576 



0-712 



8-51 



0-91 



o-oi 



001 



000 



1874 



0-875 



8-80 



1-08 



0-O15 



0-015 



o-oo 



2184 



0-996 



8-59 



1-26 



025 



0025 



00 



2245 



1-057 



8-85 



1-30 



0025 



0025 



o-oo 



2450 



1-118 



8-59 



1-42 



003 



0035 



-0-005 



2512 



1-151 



8-65 



1-45 



0-04 



004 



o-oo 



2804 



1-287 



8-66 



1-62 



006 



0-06 



o-oo 



2996 



1-366 



8-58 



1-73 



0-075 



08 



-0005 



3176 



1 -468 



8-70 



1-84 



010 



0-105 



-0-005 



3369 



1 -559 



8-72 



1-95 



0-14 



0-135 



4-0-005 



3532 



1-624 



8-66 



2-04 



017 



0165 



4-0-005 



3752 



T713 



8-60 



2-17 



0-215 



0-22 



-0-005 



4272 



1-952 



8-63 



2-47 



043 



435 



-0-005 



4513 



2-060 



8-60 



2-61 



0-58 



0-595 



-0-015 ' 



4736 



2-152 



8-56 



2-74 



0-725 



0-79 



-0065 



4849 



2-217 



8-63 



2-81 



092 



92 



000 



5015 



2-268 



8-54 



290 



1-125 



1-12 



+ 0-005 



5040 



2-290 



8-56 



2-91 



1-205 



1145 



+0-06 



5165 



2339 



8-53 



2-99 



1-335 



1-36 



-0-025 



5205 



2 362 



856 



301 



1-435 



1-415 



+ 0-02 



5256 



2-401 



8-62 



3-04 



1-51 



1-515 



-0-005 



5205 



2-433 



8-81 



301 



1-49 



1-415 



! 



+ 0-075 



I 



I 



The last readings were obtained after the condenser had been 

 charged for two successive periods of 5 minutes each. The- 

 condensers were discharged at the end of the first period, 

 but a spark at the key prevented a reading of Y being ob- 

 tained ; they were immediately charged again and, at the 

 end of a further period of 5 minutes, the figures given were 

 obtained. It will be seen that a slight increase in both 

 h and C was obtained, but the changes were almost within 

 the limits of possible error and further measurements are 

 desirable. The}' are, however, attended with considerable 

 risk of piercing the mica. The hysteresis effect is clearly 

 shown in the following figures, which were obtained by 

 charging the condenser to about 5300 volts and allowing 



I 



