ON THE MAGNETIC QUALITIES OF IRON. 1031 
about by reversals of a magnetizing force will be found in the experiment of fig, 32. 
Fig. 32. 
This experiment, like the last, was made with a magnetic curve-tracer in which the 
metal under examination had two independent magnetizing colls wound on it. 
Through one of these, Q, a current was passed which, when acting alone and carried 
through a cycle of values, gave the usual curve cibcd, the dotted line ab being obtained 
after the metal had been neutralized by reversals in the usual way. Next the current 
in Q was brought to some steady value and a violent molecular shaking was produced 
by rapid reversals of a current in P which, starting with a rather high value, was 
gradually reduced to zero while a rapid reversing key in its circuit was kept in 
motion. It would be inappropriate to call this process by the accustomed name (of 
“demagnetising by reversals”) inasmuch as its effect was to leave the iron more or 
less strongly magnetized in consequence of the existence of the constant magnetizing 
force due to the current in Q. The maximum magnetizing force produced in this 
process of reversals by the current in P wms about equal to the maximum force which 
was excited by the current Q at the extreme point h of the curve. Reversals of a 
force beginning with this high value and decreasing to zero gave the metal so thorough 
a molecular shaking up that the magnetizing ejffect of the steady current became, 
under their influence, almost wholly independent of the previous magnetic history of 
the piece. In other words the effects of hysteresis nearly disappeared. The points 
marked thus -{■ in fig. 32 were obtained in this way. They represent the relation of 
