316 ROTATION BY ELECTRICITY. SECT. XXXI. 



came constant. Under the same circumstances the 

 south pole of the magnet rotates from right to left. It 

 is evident from this experiment, that the wire may also 

 be made to perform a rotation round the magnet, since 

 the action of the current of electricity on the pole of the 

 magnet must necessarily be accompanied by a corres- 

 ponding reaction of the pole of the magnet on the elec- 

 tricity in the wire. This experiment has been accom- 

 plished by a vast number of contrivances, and even a 

 small battery, consisting of two plates, has performed 

 the rotation. Dr. Faraday produced both motions at 

 the same time in a vessel containing mercury ; the wire 

 and the magnet revolved in one direction about a com- 

 mon center of motion, each following the other. 



The next step was to make a magnet, and also a cyl- 

 inder, revolve about their own axes, which they do with 

 great rapidity. Mercury has been made to rotate by 

 means of Voltaic electricity, and Professor Ritchie has 

 exhibited in the Royal Institution the singular spectacle 

 of the rotation of water by the same means, while the 

 vessel containing it remained stationary. The water 

 was in a hollow double cylinder of glass, and on being 

 made the conductor of electricity, was observed to re- 

 volve in a regular vortex, changing its direction as the 

 poles of the battery were alternately reversed. Pro- 

 fessor Ritchie found that all the diiferent conductors 

 hitherto tried by him, such as water, charcoal, &c., give 

 the same electro-magnetic results when transmitting the 

 same quantity of electricity, and that they deflect the 

 magnetic needle in an equal degree, when their res- 

 pective axes of conduction are at the same distance from 

 it. But one of the most extraordinary effects of the 

 new force is exhibited by coiling a copper wire, so as to 

 form a helix or corkscrew, and connecting the extremi- 

 ties of the wires with the poles of a galvanic battery. 

 If a magnetized steel bar or needle be placed within the 

 screw, so as to rest upon the lower part, the instant a 

 current of electricity is sent through the wire of the 

 helix, the steel bar starts up by the influence of this in- 

 visible power, and remains suspended in the air in op- 

 position to the force of gravitation (N. 218). The effect 

 of the electro-magnetic power exerted by each turn of 



