1032 
PROFESSOR J. A. EWING AND :^[TSS H. G. KLAASSEN 
B to the magnetizing force after reversals of an auxiliary force had been used to 
produce violent molecular agitation. Some of the points are marked thus ©, and in 
these cases the process of magnetic shaking was performed after the steady current had 
been so manipulated as to lead to a point on the descending limb of the ordinary cyclic 
curve : the application of reversals then brought the magnetism down to the marked 
value. On the other hand the points marked + were reached by applying reversals 
to raise the magnetism from a point on the ascending limb of the main cycle. It 
will be seen that the points marked © lie as nearly as possible on the same smooth 
curve with those marked +. That is to say, the effects of hysteresis are obliterated 
by this method of agitating the metal even more completely than they are obliterated 
by mechanical vibration in soft iron."^ Ascending and descending limbs alike become 
merged on the single curve ae. 
Fig. 33. 
Magnetic curve-tracer curves for soft iron bars. 
(а) Cjcle performed slowly. 
(б) Period of cycle 3 seconds. 
(c) Period of cycle 0'43 second. 
Keference has been made above to the evidence of time-lag in magnetization which 
the magnetic curve tracer furnishes. It is in the softest iron that these are most 
apparent, and especially'' when the pieces under test are solid or imperfectly laminated. 
When solid rods of soft iron are used, three quarters of an inch or so in diameter, the 
* Compare a corresponding' expei-iment in which tapping was found to make the ascending and 
descending limbs of the magnetic cycle approach coincidence, ‘ Phil. Trans.,’ 1885, Part II. p. 564-566. 
