156 MR. FARADAY’S EXPERIMENTAL RESEARCHES IN ELECTRICITY. 
119. The experiments described combine to prove that when a piece of 
metal (and the same may be true of all conducting- matter) is passed either 
before a single pole, or between the opposite poles of a magnet, or near electro- 
magnetic poles, whether ferruginous or not, electrical currents are produced 
across the metal transverse to the direction of motion; and which therefore, in 
Arago’s experiments, will approximate towards the direction of radii. If a 
single wire be moved like the spoke of a wheel near a magnetic pole, a cur- 
rent of electricity is determined through it from one end towards the other. 
If a wheel be imagined, constructed of a great number of these radii, and this 
revolved near the pole, in the manner of the copper disc (85.), each radius will 
have a current produced in it as it passes by the pole. If the radii be sup- 
posed to be in contact laterally, a copper disc results, in which the directions 
of the currents will be generally the same, being modified only by the coaction 
which can take place between the particles, now that they are in metallic 
contact: 
120. Now that the existence of these currents is known, Arago’s pheno- 
mena may be accounted for without considering them as due to the formation 
in the copper of a pole of the opposite kind to that approximated, surrounded 
by a diffuse polarity of the same kind (82.) ; neither is it essential that the 
plate should acquire and lose its state in a finite time; nor on the other hand 
does it seem necessary that any repulsive force should be admitted as the cause 
of the rotation (82.). 
121. The effect is precisely of the same kind as the electro-magnetic rota- 
tions which I had the good fortune to discover some years ago*. According 
to the experiments then made, which have since been abundantly confirmed, 
if a wire (PN, fig. 2G.) be connected with the positive and negative ends of a 
voltaic battery, so that the positive electricity shall pass from P to N, and a 
marked magnetic pole N be placed near the wire between it and the spectator, 
the pole will move in a direction tangential to the wire, i. e. towards the right, 
and the wire will move tangentially towards the left, according to the direc- 
tions of the arrows. This is exactly what takes place in the rotation of a plate 
beneath a magnetic pole ; for let N (fig. 27.) be a marked pole above the cir- 
cular plate, the latter being rotated in the direction of the arrow: immediately 
* Quarterly Journal of Science, vol. xii. pp. 74. 186. 416. 283. 
