194 MR. FARADAY’S EXPERIMENTAL RESEARCHES IN ELECTRICITY. 
is stationary, then currents are produced. All the results obtained with the 
galvanometer are more or less of this nature, the galvanometer extremity being 
the fixed part. Even those with the wire, galvanometer, and earth (170.), may 
be considered so without any error in the result. 
261. If the motion of the metal be in the same direction, but the angular 
velocity of its parts relative to the pole of the magnet different, then currents 
exist. This is the case in Arago’s experiment, and also in the wire subject to 
the earth’s induction ( 172 .), when it was moved from west to east. 
262. If the magnet moves not directly to or from the arrangement, but late¬ 
rally, then the case is similar to the last. 
263. If different parts move in opposite directions across the magnetic 
curves, then the effect is a maximum for equal velocities. 
264. All these in fact are variations of one simple condition, namely, that all 
parts of the mass shall not move in the same direction across the curves, and 
with the same angular velocity. But they are forms of expression which being 
retained in the mind, I have found useful when comparing the consistency of 
particular phenomena with general results. 
Royal Institution , 
December 21, 1831. 
