ox THE MAGXETIZATTOX AND RETEXTTVEXESS OF XTCKEL. 309 



the wire. The susceptibility of the wire that has been twisted is 

 in general diminished to a slight extent, although in one or two 

 places, it is increased. 



Further experiments made by subjecting the wire to longitudinal 

 stresses of 5.14 and 10.14 legs, gave the same general results. The 

 curves are shown in Fig. o and Fig. 4 respectively. All the curious 

 characteristics are the same as l)efore. Comparing the curves for un- 

 twisted with the curves for twisted wire, we see how marked is the 

 difference between these two conditions, and especially when the wire 

 is subjected to considerable longitudinal stresses. The curves show 

 very readilv that the magnetic susceptibility for a field of 27 units of 

 the untwisted wire with a load of 5 kgs. is only one half the suscep- 

 tibility for the same witli a twist of 1° per cm. lîut judging from 

 the march of the curve, we may safely conclude that the susceptibility 

 of the untwisted wire will liecome greater than that of the twisted 

 wire, when tlie strength of the field is sufficiently incrensed. With a 

 load of 10 kgs., the susceptibility of the wire whicli has suifered a 

 torsion of 3° per cm. is 3 times as great as that of the untwisted wire 

 even at the field of 27 units. 



Another thing to he noticed is the receding of tlie " Wendepunkt" 

 for the twisted wire under heavy load. This point tends to move 

 gradually towards the right as the load is increased at constant twist. 

 This is not so well marked in the first two experiments, ])ut is cpiite 

 apparent wlien the longitudinal stress amounts to .î or 10 kgs. Thus 

 for the unloaded wire with a twist of 1° per cm., the " Wendepunkt" 

 lies at .^ = 6.3, wdiile for the wire under the longitudinal stress of 5 

 kgs., it occurs at .0 = 12. Similarly for a wire witli a twist of 3° per 

 cm., the " Wendepunkt" occurs at » = 4..S for the unloaded, and .at 

 iQ :^ 11 for the loaded wire. This is still more marked when the wire 

 is loaded with 10 kgs. 



