THE PRESSURE UPON THE POLES OF THE ELECTRIC ARC. 



117 



TABLE V. (BURNHAM). Direct Current. Variation of Total Pressure with Current 

 and Arc-length. After Correction for Earth's Field and Electromagnetic Effects. 



10 



0-90 

 0-83 

 0-73 



0-G3 



0-30 0-55 

 0-26 



0-43 

 0-20 



0-45 



1-55 



TABLE VI. (BURNHAM). Direct Current. Variation of Total Pressure with the 



Current for two given Arc-lengths. 



DIRECT CURRENT. SERIES C. 



Observer: Mr. A. H. DAVIS. 



The arrangement shown in fig. 9 was adopted ; the moment of inertia of the arm 

 was reduced by moving the balance weight very close to the centre of the swinging 

 arm, and a vane dipping into water was added to damp the oscillations. The double- 

 arc method was adopted because it eliminated the electromagnetic effects upon the 

 movable parts of the circuit due to the earth's field and to the rest of the circuit ; 



VOL. ccxx. A. s 



