08 ART. 4. — K. HONDA AND T. TEEADA. 



If a be the coefficient of thermal exj^ansion, 



Thus the change of the coefficient of thermal expansion by mag- 

 netization is equal to the temperature coefficient of the magnetic 

 elongation. As the latter coefficient is known from the experi- 

 ment* by Mr. S. Shimizu and one of us, the values of da are 

 calculated and graphically drawn in Figs. 78, 79, 80, 81 and 82. 



By referring to the figures, we see that the change of the 

 coefficients of thermal expansion by magnetization depends con- 

 siderably upon temperature. Ordinatcs of the curves represent 

 the change of the mean coefficient of expansion between two 

 temperatures belonging to each curve. 



The change of the mean coefficient of expansion in nickel 

 (Fig. 78) betw^een the ordinary and liquid air temperatures first 

 decreases, attains a minimum, and then gradually increases, as 

 the field becomes greater, till it is greater than its initial 

 value. At a temperature higher than the ordinary, the change 

 of the coefficient of expansion steadily increases, soon aj^proaching 

 an asymptotic value. In a given field, its value increases wàth 

 temperature, and after passing through a maximum, slightly de- 

 creases. The maximum amount of the change is of the order of 

 19^ of the coefficient itself. 



In soft iron and tungsten steel (Figs. 79 and 80), the change 

 of expansion is very small. Up to a moderate temperature, the 

 coefficient of expansion increases steadily with the field, except in 

 weak fields, in which a small decrease is observed. At higher 

 temperatures, the change becomes negative for all fields. In iron, 

 a maximum decrease is observed. 



*} K. Honda and S. Shinuzu, Jour. .Sc. Coll., XX, Art. 10, I'JOC 



