488 Lieut. G. 0. Squier on the Electrochemical 



time, and the fluctuation of the original deflexion caused by 

 this treatment. The strength of field was about 11,000 H., 

 and the experiment was conducted without compensating the 

 original deflexion, and by making the field for one minute, 

 then breaking for one minute, and so on. 



One of the curves is shown in fig. 1 (III.), in which posi- 

 tive ordinates are values of the concentration throw at " make," 

 and negative ordinates the values of the " protective throw/' 



Experimenting was not begun until the gelatine had com- 

 pletely hardened, and since the electrodes w r ould tend to 

 become polarized while the gelatine was hardening, the " pro- 

 tective throw" was very small, and soon masked by the 

 concentration effects. 



After about five minutes, making the field had very little 

 effect at all, but began to show decided " concentration 

 throws " ten minutes later, and these rapidly increased with 

 time, as the curve indicates. 



Considering the fluctuation of the original deflexion, the 

 effect of this periodic field was to tend to reverse it, just as in 

 the case of the uniform field in experiment B, but much more 

 slowly, since the field was on but half the time in this case. 



The cell also showed the iron salts almost entirely about the 

 point, forming a thick black envelope. 



I. Summary. 



The principal results of this investigation may be sum- 

 marized as follows : — 



Whenever iron is exposed to chemical action in a magnetic 

 field, there are two directly opposite influences exerted. 



(a) The direct influence of the magnetized condition of the 

 metal, causing the more strongly magnetized parts to be 

 protected from chemical action. 



This is exhibited in the phenomenon of the " protective 

 throw," which is always in the direction to protect the more 

 strongly magnetized parts of magnetic electrodes. 



The " protective throw " is small, often requiring delicate 

 apparatus to detect it, and is soon masked by the secondary 

 concentration effects. 



As to the absence of the ei protective throw " with acids 

 which attack iron with the evolution of hydrogen, the 

 hydrogen acts merely mechanically, and when removed by 

 adding to the solution small quantities of hydrogen dioxide, 

 the " protective throw " becomes very decided. 



In the curve, fig. 2, representing the variations of the 

 " protective throw " with the strength of the magnetic field, 





