128 



Prof. W. M. Thornton on the 



3. Organic Insulators. 



The relation holds equally well for complex organic 

 materials. 



Table V. — Vulcanized Indiarubber *. 

 A=5-16.10- 6 . B = 3-9.10- 10 . A/B = 13,200. 



Thickness. 



Breakdown "Voltage. 



Diff. per 

 cent. 



Observed. 



Calculated. 



0-1 cm. 



0-2 



0'3 



0-4 



0-7 



10,000 

 16,800 

 22,000 

 26,000 

 34,800 



10,670 

 16,970 

 21,920 

 20,000 

 36,300 



4-6-7 

 +0-9 

 -0o 

 00 

 +6'8 



Table VI. — Impregnated Jute f. 

 A=2-1.10- 5 . B = l-9.10- 9 . A/B = 11,000. 





Breakdown Voltage. 





Thickness. 





Diff. per 









Observed. 



Calculated. 



cent. 



0-1 cm. 



2,300 



2,240 



-20 



•2 



3,500 



3,690 



+5-5 



•3 



4,500 



4,865 



+8-0 



•4 



5,500 



5,850 



+6-5 



•7 



8,000 



7,830 



-1-9 



10 



10,200 



10,290 



+09 



1-3 



12,200 



12,040 



-1-2 



1-6 



14.000 



13,540 



-30 



20 



16,200 



15,340 



-5-4 



A=9 



Table VII. — Presspahn %. 

 10- 6 . B = l-37.10- 9 . A/B = 6550. 





Breakdown Voltage. 





Thickness. 





Diff. per 









Observed. 



Calculated. 



cent. 



•01 cm. 



960 



960 



o-o 



•02 



1,750 



1,760 



4-0-5 



•03 



2,500 



2,430 



-2-7 



•04 



3,100 



3,040 



-1-9 



•05 



3,650 



3,600 



-1-4 



•06 



4,100 



4,100 



4-0-2 



•07 



4,500 



4,480 



-0-2 



•08 



4,900 



5,030 



4-2-5 



r. 7. 



* Siemens and Baur, Jour. Inst. E. E. xxi. 1892, p. 183, fig. ' 

 t Baur, ' Das Elektrische Kabel,' p. 44, and Jour. I. E. E. xxi. 1892, 1, c. 

 % L. A. Lewis, " Testing of Continuous Current Machinery," I. E. E. 

 March 16, 1904. 



