47-4 Lieut. G. 0. Squier on the Electrochemical 



copper being deposited in lines approximating to the equipo- 

 tential lines of tie magnet, and the outlines of the pole being 

 distinctly marked by the absence of deposit. 



Messrs. Nichols and Franklin * were the next to conduct 

 experiments bearing on this subject. They found that finely 

 divided iron which has become " passive " through the action 

 of strong nitric acid suddenly regains its activity when intro- 

 duced in a magnetic field, and also that when one of the two 

 electrodes immersed in any liquid capable of chemically 

 acting upon them is placed in a magnetic field, a new 

 difference of potential is developed between them due to this 

 magnetization. They ascribe these effects to electric currents 

 in the liquid produced indirectly by the magnet, which 

 currents go in the liquid from the magnetized to the neutral 

 electrode. 



Professor Rowland and Dr. Louis Bell f were the first to 

 note the " protective action " of points and ends of magnetic 

 electrodes, and to give the exact mathematical theory of this 

 action. Their results were directly opposite to those of 

 Messrs. Nichols and Franklin, who found, as stated above, 

 that points and ends of bars in a magnetic field acted like 

 zincs to the other portions, or were more easily dissolved by 

 the liquid. 



The method of experiment adopted by Professor Rowland 

 was to expose portions of bars of the magnetic metals placed 

 in a magnetic field to reagents which would act upon them 

 chemically, and study the changes in the electro-chemical 

 nature of the exposed parts by fluctuations in a delicate 

 galvanometer connected with the two bars. Iron, nickel, and 

 cobalt were experimented upon, and nearly thirty reagents 

 were examined in this manner. The results are summed up 

 in the following statement : — " When the magnetic metals 

 are exposed to chemical action in a magnetic field, such 

 action is decreased or arrested at any points where the rate of 

 variation of the square of the magnetic force tends towards a 

 maximum." 



Other investigations in this field are those of Andrews J, 

 w T ho employed iron and steel bars from eight to ten inches 

 long with their ends immersed in various solutions, and one 

 bar magnetized by means of a solenoid. The protective 

 action was not noted, but, on the contrary, the magnetized 



* American Journal of Science, vol. xxxi. p. 272, vol. xxxiv. p. 419, 

 vol. xxxv. p. 290. 



t Phil. Mag. vol. xxvi. p. 105. 



% Proceedings of the Koyal Society, no. 44, pp. 152-168, and no. 46, 

 pp. 176-193, 



