to the left into the position previously occupied by A, and D moves to the right into the position previously occupied by B. But the charge on C is of the same sign as that with which A started the process, and will therefore act in the same sense, only more strongly, since it has been reinforced by the inductive action just explained. Thus during rotation of the two rows of segments in opposite sense the original very slight electrification is rapidly increased, and a considerable quantity of electricity may be taken off by the action of the collecting combs and accumulated on the electrodes. It will be observed that the segments of both discs, whilst passing each other on the horizontal diameter, are charged with electricity of the same sign, namely, positive on the left and negative on the right.
If we now inquire as to the true cause of electrification, we find that apart from the quite insignificant initial charge on A and B, it is simply the mechanical energy required to produce rotation against the opposing force of electrostatic attraction between the outer and inner segments. A has a positive, and a has a negative charge. These two segments therefore attract each other; as a moves to the right and A to the left, they are
