DESCRIPTION OF THE PHENOMENON. 



CHAPTER II. 



OF THE TIDAL MOTIONS OF MOVABLE ELECTRIC CONDUCTORS. 



(From the Journal of the Franklin Institute for January, 1836.) 



CONTENTS : Description of the Phenomenon. The Polar Wires act as Centres of At- 

 traction. They produce Tides. Cause of the Oscillations. Cause of the Spiral 

 Motions. 



18. "DANS d'autres circonstances on observe encore au milieu des masses liquides, 

 des mouvemens singuliers qu'il est excessivement difficile de decrire, tant ils sont nom- 

 breux et changeans. Je vais essayer d'en donner une idee, en remarquant toutefois, 

 qu'apres avoir fait de nombreuses experiences sur ce sujet, il rn'a etc impossible d'en 

 saisir la loi." (Pouillet^) 



19. The singular movements here spoken of by Pouillet have likewise drawn the 

 attention of several other philosophers. Erman and Serullas have both recorded in- 

 stances of gyratory motion produced in certain bodies, especially mercury, by the con- 

 tact of others. There is also a similar observation made by some of the earlier chem- 

 ists respecting camphor. Strange motions of an analogous description are also ob- 

 served in some liquids under the influence of a voltaic current ; these, in the case of 

 mercury, have been particularly studied by Sir J. Herschel, who obtained several re- 

 markable notices respecting them ; they are, however, so far as I am informed, as yet 

 without explanation. 



20. If into a watch-glass or shallow capsule, as a a (Jig. 5, pi. 1), fifty or sixty 

 grains of mercury be poured, and over that as much water, acidulated with sulphuric 

 acid, as is sufficient to cover the surface of the mercury, and the positive and negative 

 wires of a battery of twenty or thirty plates, arranged as indicated, the mercury being 

 in contact with the negative pole, and the positive pole being plunged into the water 

 at a short distance from it, currents are produced both in the water and in the mercury. 

 Supposing the power of the battery sufficient, the same effect takes place on removing 

 the negative wire out of the mercury into the water; but if the positive wire is in con- 

 tact with the mercury, and the negative with the water, there is no motion at all, or, at 

 most, the mercury only curls itself up into an elongated figure. 



21. This motion varies according to several circumstances, but chiefly from the po- 

 sition of the two wires. 1st. If the wires be on opposite sides of the mercury, the metal 

 instantaneously elongates, and currents also are seen playing in the water. 2d. If the 

 negative wire be introduced into the centre of the metallic globule, and the positive 

 wire be brought on one side, the mercury will bulge out elliptically at both sides, near- 

 est and farthest from the positive pole ; and by regulating the force of the battery, either 

 by changing the number of the plates, or altering the strength of the solution acting on 

 them, the experiment may be so managed that no motion shall ensue in the mercury 



