EFFECT OF TWIST ON THE MAGNETIZATION OF NICKEL AXD [RON. 197 



noticed before for the smaller twists. On increasing the field to 

 20.8 units, another change takes place in the magnetization curve. 

 The points of minimum magnetization on both twisting and untwis- 

 ting have vanished altogether, the magnetic intensity always diminish- 

 ing in the former, while it increases in the latter. At the same time, 

 the original double looped curve becomes contorted, und the going 

 and returning curves cross each other. But as soon as this stage is 

 past, the increase of magnetizing force makes the four loops of the 

 magnetization curve collapse into two, and hereafter the curve wears 

 the genera] aspect as shown in Fig. 11. 



diminution of magnetization by twisting in strong magnetizing fields. — 

 The fact that the magnetization diminishes instead of rising when 

 twisted in high magnetizing fields, can be explained from the nature of 

 the curves of magnetization for different I wists. In my former paper,* 

 it was shown that beyond a certain strength of the field, the suscep- 

 tibility of the twisted wire diminishes mon; rapidly than that of the 

 untwisted, so that the magnetic intensity is in general smaller for the 

 twisted than for the untwisted. Thus we should be led to expect a 

 diminution of magnetization on twisting, and increase on untwisting, 

 and the curve will have the appearance as in Figs. 7, 8, and 11. But 

 this does not throw any light on the reason for the change of sign of 

 hysteresis between the cases represented by Figs. 10 and 11. 



Reversal of hysteresis occurs in lower magnetizing fields as the hoist is 

 taken larger. — The preceding experiments for the twist of 1°.5 le>] me 

 to suspect that the strength of the magnetizing force as well as the 

 amount of twist formed a chief cause of the reversal of hysteresis, 

 and is not due to the difference in nickel. To test this, a thin wire 

 35 cms. long was twisted through :': 1.7 per cm. The curve (Fig. 



* Magnetization and retentiyeness of nickel wire under combined torsional and longitudi- 

 nal stresses. This Journal, Vol. IT. 



