Effects due to Magnetization. 451 



behavior of the cell in the two experiments described is prin- 

 cipally due, either directly or indirectly, to the distribution of 

 the iron salts formed by the reaction in the two cases. 

 The principal time effects of the magnet were : 



(a) To produce a higher potential at the point of greater magnet- 

 ization. 



(5) To increase the rate of change of the potential between the 

 electrodes and the absolute value of this potential difference. 



(c) It also appears from both curves that after a certain distribu- 

 tion of iron salts is reached, farther presence of the same does 

 not effect the permanency of the current established. 



Since the time effects of the magnet were so marked, it was 

 thought possible that a " cumulative " effect, due to the Earth's 

 Held alone might be detected after a sufficient time had elapsed. 

 The apparatus was made as delicate as possible, and parallel ex- 

 periments conducted, the electrodes first being placed in the 

 magnetic meridian, and afterwards perpendicular thereto. ~No 

 positive difference could be detected. 



C. Convection currents in the liquid. 



As has already been stated, the reversal of the current which 

 regularly followed the " protective throw " was found by 

 Messrs. Rowland and Bell to wholly disappear when hardened 

 acidulated gelatine was substituted for the dilute acid solution, 

 so that when the magnet was put on, a permanent deflection 

 of much less magnitude was obtained instead of a transitory 

 throw. This indicated that currents in the liquid cannot be 

 neglected, and their study was next undertaken. Since hard- 

 ened gelatine completely prevented the reversal of the current, 

 and with no gelatine it regularly appeared after a short time, 

 a large number of experiments were made, in which the amount 

 of gelatine was varied continuously between these limits. As 

 expected the effects also varied, the greater the fluidity of the 

 solution, the more quickly the reversal occurred. 



In the light of what was already known concerning the 

 presence of iron salts, some of the experiments were continued 

 over a considerable time, and in others iron salts were intro- 

 duced artificially, to increase the effects. It was soon found 

 that by starting with a fresh hardened gelatine, with which 

 the " protective throw " was the only feature, and gradually 

 increasing the fluidity of the solution and the amount of iron 

 salts present, both effects were exhibited at the making of the 

 field, first, the sudden throw of the needle always in the direc- 

 tion to protect the point, and immediately thereafter the com- 

 paratively slow " concentration throw " in the opposite direc- 



