250 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



this correction on the ground that it might not be the same for the 

 reversal of the solenoid as for the reversal of toroid, one would find 

 occasionally the reversals consisting of the larger number of steps 

 giving a slightly greater flux change than the 1-step reversals. I have 

 made the correction wherever it entered. 



Figure 12. 

 reversals. 



5 REVERSALS 10 15 X. 



Set I: B 3000: tenth magnetization; O indicates 1-step 



The throw, 7.5.3, due to the first application of the field was ex- 

 pressed in terms of degrees, doubled and changed again to a throw in 

 centimeters in order that it might be on the same scale as the reversals. 

 It is plotted as the zero reversal. 



The 6th, 22d, and 24th are 5-step reversals. For each separate step 

 of each of these the angular displacement of the coil was calculated. 

 The five angles of any one reversal were added and turned again into 

 centimeters throw of the galvanometer. A curve, Figure 13, was 

 plotted from the 1-step reversals; millimeters were plotted throughout 

 instead of centimeters. The 5-step reversals were added after the 

 curve had been drawn in order that any variation might appear more 

 plainly. 



All the curves of the following six sets were obtained by the same 

 method. 



