ox THE MAGNETIZATION AND KETENTIVENESS OF NICKEL. 



317 



.89 instead of .74. However, this large retentiveness occurs just at 

 the field wliere the susceptibiHty is at its maximum. Tlie rate at 

 which this ratio grows with the field is almost uniform till the maxi- 

 mum is reached, if we leave out of account the observations at very 

 low fields which caimot in the circumstances be regarded as at all 

 accurate. The curves in Fig. 5,, are therefore straight up to the 

 maximum. For the twisted wire the maximum is passed very abrupt- 

 ly ; and for the rest of their course all the curves are approximately 

 straight lines. 



With a twist of 1°.5 per cm, the amount of residual magnetism 

 increases still more ; and at the maximum point which again occurs 

 near the Wendepunkt, the ratio of the residual to the temporary attains 

 the value of .98. It is indeed wonderful what a great eftect simple 

 twisting of nickel produces upon its retentiveness. The approach to 

 the maximum ratio takes place more suddenly in this than in the 

 previous case, the curve sloping more steeply. There is nothing sin- 

 gular after the maximum is passed, but the rate of fixll for higher 

 fields becomes distinctly less for the lai'ger twist. When the twist is 

 increased to 4°.5 or 9° per cm, there is a distinct tendency in the curve 

 to return to its former state. Thus the slope gradually becomes less 

 steep, and the maximum occurs at higher fields. But the ratio of the 

 residual to the temporary magnetism still keeps to its late value. 

 Again the rate of fall of the ratio after the maximum is reached grad- 

 ually lessens as the twist is increased. 



From these experiments, we gather that twist applied to nickel 

 wire increases its residual magnetism, which attains a maximum in 

 the field corresponding to the maximum suscejitibility. For moderate 

 twists this maximum residual falls short (jf the temporary magnetism 

 by only 2 per cent. The sooner the '■ Wendepunkt " occurs, the 

 more rapid is the rate of increase of the residual magnetism ; and 



