10 ART. 10.— K. HONDA & S. SHIMIZU. 



Cast cobalt. The results of observation in cast cobalt are 

 drawn in Fig. 9. As the temperature is raised, the magnetic con- 

 traction in weak fields gradually lessens, and the elongation in strong 

 fields increases, till it reaches a maximum. At temperatures higher 

 than 800°C, the initial contraction altogether disappears and the 

 course of the curves resembles that of iron and steel at high tem- 

 peratures. If the temperatures be further increased, the elongation 

 diminishes steadily, but at a diminishing rate, and even at such a 

 high temperature as 1020°C, we still observe a considerable elongation 

 of the metal. From the course of the curves in Fig. 10, it is easy to 

 see that in H = 800, the elongation does not vanish up to a tem- 

 perature of 1200°C, which is higher than its critical temperature by 

 100°C. With our arrangement, it was not possible to push the 

 experiments still further, as the melting point of copper was not far 

 from that temperature. It is also to be observed that the field of 

 maximum contraction gradually decreases as the temperature is 

 raised, and that the temperature of maximum elongation in a given 

 field diminishes as the field is increased. 



With the same specimen, the effect of high temperature was 

 first studied, and when the specimen was cooled down to its initial 

 temperature, it totally changed its character with regard to the 

 magnetic change of length. It was therefore not possible to examine 

 the effect of cooling of the metal in the cast state. 



Annealed cobalt. The specimen was annealed in a charcoal 

 fire lor about 4 hours, being carefully wrapped in asbestos papers. 

 The effect of high temperatures on the magnetic change of length in 

 annealed cobalt presents an extraordinary feature, as may be seen 

 from Fig. 11. As the temperature is raised, beginning with that 

 of liquid aii-, the contraction increases at first slowly and then 

 rapidly, 'ill it reaches a maximum. It then decreases and 



