482 Lieut. G. 0. Squier on the Electrochemical 



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

 was thought possible that a (i cumulative " effect, due to the 

 earth's field alone, might be detected after a sufficient time 

 had elapsed. The apparatus was made as delicate as possible, 

 and parallel experiments conducted, the electrodes first being 

 placed in the magnetic meridian, and afterwards perpen- 

 dicular 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. Eowland and Bell to wholly disappear when har- 

 dened acidulated gelatine was substituted for the dilute acid 

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

 deflexion 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 hardened 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 

 direction to protect the point, and immediately thereafter the 

 comparatively slow " concentration throw " in the opposite 

 direction. By making the conditions still more unfavourable 

 for the " protective throw," it gradually diminished until en- 

 tirely masked by the second effect, so that making the field 

 produced a deflexion in the direction indicating a current 

 from the point. 



With the proper conditions, both of these effects could be 

 studied with the greatest ease : first, one made prominent, 

 then both equal, then the other made prominent at will. The 

 " protective throw " could be traced until it became a mere 



