•±54 G. 0. Squier — Electro- Chemical 



point. This, at least partially, accounted for the sudden effects 

 often noticed at breaking the field circuit, and the compara- 

 tively small ones at " make " especially with certain salt solu- 

 tions, such as copper sulphate. 



The outer envelope which held the iron salts together, and 

 limited the immediate influence of the magnetized point, was 

 distinctly defined within the liquid, and easily observed by the 

 reflection of the light from its convex surface. 



The persistency with which the iron salts were held about 

 the point was shown by moving the cell with respect to the 

 electrodes, when the contour remained approximately intact, 

 passing bodily through the liquid without being broken up. 



JE. Electromagnetic rotations. 



The small dust particles present in the liquid were drawn 

 radially toward the point until they reached the surface de- 

 scribed, When they pierced it and began to revolve rapidly 

 about the point inside this surface, in the opposite direction to 

 the currents of Ampere. Reversing the poles of the magnet, 

 produced surfaces of the same appearance, but opposite rota- 

 tions. 



When the current from a Daniell cell was sent through, it 

 seemed to have very little effect upon the rotations, showing 

 them to be controlled by the powerfully magnetized point. 



The electromagnet was arranged with its field vertical, and 

 the point electrode along the lines of force as before. This 

 arrangement gave better control of the surfaces formed, since 

 gravity now acted symmetrically about the point. 



When a single iron rod about 3 mm in diameter, and placed 

 vertically in the cell, was substituted for the two electrodes, 

 two rotations were observed, which were uniformly dextro 

 about the north-seeking pole of the rod, and lsevo about the 

 south-seeking pole. About the central neutral portion no rota- 

 tions were observed. When the rod was covered with a thin 

 coating of vaseline, the rotations entirely disappeared as ex- 

 pected. Wartmann* observed similar rotations about soft iron 

 cylinders adhered to the poles of a magnet, and he ascribed 

 them to electric currents in the liquid which proceed from the 

 periphery of the cell radially to the surface of the rod. 



The explanation of these rotations follows at once from 

 what we know of the time effects produced by the magnet. 

 A higher potential is always produced at points of greater 

 magnetization, causing electric currents in the liquid from the 

 more strongly magnetized to the weaker parts of the iron. 



* Philosophical Magazine, xxx, 184*7, p. 268. 



