421 

 TABLES 429-452.— SOME CHARACTERISTICS OF DIELECTRICS 



TABLE 429.— STEADY POTENTIAL DIFFERENCE IN VOLTS REQUIRED TO 

 PRODUCE A SPARK IN AIR WITH BALL ELECTRODES (RADIUS R) 



TABLE 430.— ALTERNATING-CURRENT POTENTIAL REQUIRED TO PRO- 

 DUCE A SPARK IN AIR WITH VARIOUS BALL ELECTRODES 



The potentials given are the maxima of the alternating waves used. Frequency, 33 

 cycles per second. 



SMITHSONIAN PHYSICAL TABLES 



