CHANGE OF RIGIDITY BY MAGNETIZATION. H 



Thus the course of the curves is less steep in cobalt than in 

 steel ; the inflexion point is not so marked in the former metal as in 

 the latter. The change of rigidity is also independent of the applied 

 couple. 



So far as we are aware, the eifect of torsion on the magnetization 

 of cobalt has not yet been studied, on account of the difiiculty of 

 getting the specimen in the forui of a wire. But if the reciprocal 

 relation holds in the case of cobalt, the above results show that the 

 effect of torsion on the magnetization of cobalt is the same as in iron. 

 We have seen from the experiment of Professor Nagaoka and one 

 of us that the character of cast cobalt ns reofards mairnetostriction is 

 remarkably different from that of annealed cobalt. The cobalt in the 

 present experiment was well annealed, ho that the above inference is 

 to be restricted to an annealed cobalt. 



6. Nickel. The chancre of ris'iditv of the nickel bar was so laro;e 

 that it was necessary to reduce the sensibility of the apparatus by 

 using a rotating cylinder of greater diameter. As in the case of 

 elasticity, we again observe in the metal the singular phenomencjn 

 that the chanofe of torsion bv mao-netizaticjn alters its siö-n as the 

 mao'netizins' force is increased. Tlie foUowinof table contains the 

 results of the observation, which are also drawn in Fig. (5. 



