PEIRCE. — BEHAVIOR OF THE CORE OF AN ELECTROMAGNET. 145 



Figure 38. 



The value of dt/di for a reverse current in a coil of the magnet Q when 

 E = 19.5 and r = 15. 



Figure 39. 



The full curve shows the rate of increase of the flux of magnetic induction 

 through the core of the magnet Q while a reverse current of 1.3 amperes is being 

 established in the exciting coil of 1394 turns. The current curve is shown on an 

 arbitrary scale by the dotted line. 



VOL. XLIII. — 10 



