RESEARCHES ON MAGNETOSTRICTION. 



365 



Iron ovoid 



Nickel rod 



These changes are plotted against H and I in Figs. 7, 8 (PI. 

 XVIII). It will be seen from these curves that the change of length 

 produced in the ovoid or in the nickel rod is similar to that observed 

 by one of us and described in the papers above cited. 



The determinations are in close agreement with the results of 

 Bidwell and several other investigators. Inspection of these curves 

 for nickel reveals a striking resemblance to similar curves for the 

 change of volume in the same metal. The behaviour of iron is 

 entirely different both as regards change of volume and change of 

 length. 



§ 3. Effect of hydrostatic and transverse pressure on the 

 magnetization of iron and nickel. 



The remarkable effect produced by longitudinal pull or compres- 

 sion on the magnetization of ferromagnetics promised the outcome 



