BABBITT. — THE VON WALTENHOFEN PHENOMENON. 



243 



practically the same hysteresis cycle. For the first eight or ten rever- 

 sals the cycle is changing rapidly and it may well be that, with the 

 iron in that condition, the number of steps taken in going from one 

 value of H to another does effect the final value of B. As it is of in- 

 terest to settle this question too, the method of investigation must be 

 changed somewhat. 



Instead of reversing the 

 field a large number of times 

 before observing the throw of 

 the galvanometer, let the 

 throw be observed when the 

 field is first applied and there- 

 after for every reversal. If 

 the first throw be regarded 

 as the zero reversal and be 

 doubled in order to make it 

 comparable with the others, a 

 throw-reversal curve may be 

 plotted as shown in Figure 4. 

 Now, with due care that the 

 demagnetizing current shall 

 not rise above the magnetiz- 

 ing current just used, let the 

 toroid be demagnetized by the 

 motor attachment. Another 

 throw-reversal curve taken 

 exactly as before wiU show 

 the manner in which the 

 iron approaches a constant 

 maximum of B on the second Figure 5. Set II: B 6000: fourth mag- 

 magnetization. A set of such netization; all are 1-step reversals except 

 curves giving the behavior of *^^ ^^^ ^^"^ ^^^ ^^*^' ^^'"^^ ^'^ ^-step. 

 the iron on the first, fourth 



fifth, sixth, seventh, and eighth magnetizations are those of Figures 4, 

 5, 6, 7, 8, and 9 respectively. 



It is evident that no two of the curves are exactly alike. The first 

 shows a sharp fall of the maximum B as the field is reversed. On the 

 other hand the second shows a rather rapid rise, as do the remainder. 

 Even so, it is not possible to pick out the same reversal on any two 

 consecutive curves and expect them to register the same flux change 

 except by chance. This is true when the curves examined consist 

 entirely of 1-step reversals up to and including the reversal in question. 



