334 Messrs. Nagaoka and Honda on Change of Volume and 



volume- change as the ovoid is annealed. The increase 

 becomes more significant as the field is made stronger. In 

 steel, the effect of annealing is greater than in iron. In 

 strong fields the volume-change of the annealed steel ovoid 

 is nearly twice as great as in the unannealed state. Wolfram 

 steel is very little affected by annealing as regards the volume- 

 change, but the change itself is several times greater than in 

 nickel or iron. In fact, the motion of the capillary meniscus 

 in the dilatometer can be easily followed by the naked eye. 

 Curves given in fig. 2 are plotted from measurements made 

 on annealed ovoids. 





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Nickel (fig. 2). — As specimens of nickel almost always 

 contain traces of iron, the change of volume will probably 

 depend on the chemical nature. In addition to this, the 

 mechanical process which the metal underwent before it was 

 brought to a form suitable for experiment must have sub- 



