14 



ART. 8.— H. N.^GAOKA AND K. HONDA: 



trend, .>5(mic\vli;it resciubliiig the inverted form of" the curve 

 showing the same change for iron and steel. If the existence of 

 the maximum elongation in iron warrants the existence of the Villari 

 point, a point of opposite character must exist in cobalt if the 

 metal be subject to loading. 



Annealed Coin ill. The cast cobalt has silvery hue, simihir to 

 nickel, only lacking the yellowish lustre of the latter. By anneal- 

 ing cobalt, the surface colour turns ashy gray, and the permeability 

 of the metal diminishes in a remarkable degree, as will be seen 

 fnjm the curves of magnetization (Fig. 1). The change of length by 

 magnetization takes place at first slowly, but goes on steadily in- 

 creasing till it amounts to nearly 25x10''' in H=2000. The 

 observed values are as follows : — 



The curve representing the change is therefore very simple, 

 approximating to a straight line. As will be found later on, we 

 found the reciprocity between the strain and the effect of stress again 



