PRODUCED BY ALTERNATING ELECTRIC CURRENTS. 
329 
a 
In fig. 56, a = 45°; in fig. 57, a = 105°; in fig. 58, a = 135°; and. in fig. 59, 
= 165°. 
Fig. 56. Fig. 57. 
2 u 
MDCCCXCII.— A. 
