450 G. O. Squier — Electro- Chemical 



minutes, and instead of again reversing, remained indefinitely 

 with the point electrode as a zinc. The distribution of the 

 iron salts in this case was quite unlike the former. Notwith- 

 standing the gelatine, the powerful magnetization of the ex- 

 posed point gradually drew the iron salts from the disc as fast 

 as they were formed, and concentrated them symmetrically 

 about the point, giving the solution in this region an almost 

 black appearance. 



After waiting a sufficient time to be assured that further 

 presence of iron salts would not effect the permanency of the 

 existing electromotive force, the magnetic field was gradually 

 decreased without ever breaking circuit, by increasing the 

 liquid resistance in the field current. This change of resist- 

 ance was necessarily made more or less suddenly, and the 

 deflection experienced at each increase of resistance, a not very 

 sudden throw toward reversal, in every respect the same as had 

 been repeatedly observed in the preliminary experiments, and 

 very different from the characteristic "protective throw" 

 which is always sudden and in one direction. 



By simply varying the field current with care, as explained 

 above, the deflection could be reversed again and again at will, 

 and could also be held at the zero of the scale indicating no 

 current at all, as long as desired. When once the field was 

 entirely broken the iron salts were released from the control 

 of the exposed pole, seriously disturbed by gravity, and put- 

 ting on the field again failed to reproduce the results noted 

 above. 



The only elements of difference in the two cases are, (a) the 

 magnetized condition of the metal, (b) the distribution of the 

 iron salts formed by the reaction. 



Although, as the curves indicate, the average electromotive 

 force with the magnetic field was much greater than in the 

 former case, yet this electromotive force is due to the differ- 

 ence of action at the two exposed surfaces, and, as will be 

 pointed out later, the total amount of iron dissolved and 

 passing into solution in the two cases is probably not very dif- 

 ferent.* Quantitative experiments are wanting on this point. 



The influence of the magnetized condition of the metal and 

 its magnitude is exhibited in the phenomenon of the "protec- 

 tive throw" which is always observed with apparatus suffi- 

 ciently delicate and unless it is masked by other secondary 

 phenomena. 



Since the electrodes were embedded in hardened gelatine, 

 there could be no convection currents in the liquid and this 

 can be eliminated. Evidently the great difference in the 



*Fossati, Bolletino dell' Elettricista, 1890. 



