396 



Mr. H. Tomlin'son on the Villari 



an alteration in the residual magnetization, but this alteration 

 does not concern us, and only the temporary changes, i.e. 

 those which take place after repeated application of the force 

 and when the deflexion on closing the battery -circuit is equal 

 to that on opening it, are recorded in the figure. 



It may be noticed that the Villari critical point depends 

 upon the load, the greater the load the smaller the critical 

 value of th.Q force. This fact has been already observed by 

 Sir William Thomson, but for a given load the Villari critical 

 point is much lower when only tbe temporary magnetization 

 is taken into account than when, as in Sir W. Thomson's 

 experiments, the whole magnetization is observed. It occurred 

 therefore to the author that though it might not be possible 

 to reach the critical force for nickel as far as the total mag- 

 netization is concerned, such a value could nevertheless be 

 found for temporary magnetization, and this has proved to be 



the case. 



Fig. 2.— Nickel. 



Fig. 2 refers to a nickel wire of "8 millim. diameter, which 

 shows Villari critical points quite as striking as those of iron, 

 but with this difference, that the critical value is greater the 



