MAGNETIC EFFECTS OF TWIST. 179 



algebraic sign of the numbers in the fourth column of Table I., there 

 is true magnetic lag. That is, the magnetic change lags behind the 

 strain which causes it. The curve is distinctly open. Passing to 

 the twist ± 7T, we see that the magnetic lag is sometimes positive, 

 sometimes negative, but is in all cases very small. Hence the curve 

 can hardly be called open, the going and returning branches being. near- 

 ly coincident. On the whole, however, as we may see by adding the 

 " lag " numbers, the lag is still positive. This twist may be regarded 

 as being almost exactly the critical twist at which the magnetic la«- 



changes sign ; for in the next curve, that for twist ± — T , the "lag" 



numbers are nearly all negative and markedly so. In fact for this 

 and for higher twists the phenomenon ceases to be one of lao-gino-, 

 but becomes really a case of what might be called magnetic "priming." 

 That is, the magnetic change, as it were, runs ahead of the straining 

 that causes it. In other words, the rate at which the longitudinal 

 magnetic intensify, whether positive or negative, falls off during un- 

 twisting from either limit to zero is greater than the rate of growth 

 during twisting, It will be noticed that the curves for the higher 

 twists are of the same character as the one given by Wiedemann 

 (Annalen d. Phys. u. Chem., Bd. XXVII., Taf. III., Fig. 8.). 



In Figure A, as given, the curve corresponding to the twist ± 8 ir 

 is not shown to the same scale as the others. It is represented to the 

 right as a dotted curve, with the scale of twist diminished to one- 

 eight and the scale of intensity diminished to two-fifths. The greater 

 openness of the curves for the higher twists, after the critical twist 

 has been passed, is very striking. At the same time it is to be noticed 

 that the range of intensity reaches a practical limit at a very moder- 

 ate twist. These peculiarities are well shown in Table II. and in 

 Figures V* and C which illustrate it. 



