98 Dr. Faraday's Experimental Researches in Electricity : 



core were to act by currents, induced for the time, in its 

 moving mass, and of the nature of those suspected (2642.). 

 If the copper cylinder moved with uniform velocity (2665.), 

 then currents would exist in it, parallel to its circumference, 

 during the whole time of its motion ; and these would be at 

 their maximum force just before and just after the to or inner 

 stop, for then the copper would be in the most intense parts 

 of the magnetic field. The rising current of the copper core 

 for the in portion of the journey would produce a current in 

 one direction in the experimental helix, the stopping of the 

 copper and consequent falling of its current would produce 

 in the experimental helix a current contrary to the former ; 

 the first instant of motion outwards in the core would produce 

 a maximum current in it contrary to its former current, and 

 producing in the experimental helix its inductive result, being 

 a current the same as the last there produced ; and then, as 

 the core retreated, its current would fall, and in so doing and 

 by its final stop, would produce a fourth current in the expe- 

 rimental helix, in the same direction as the first. 



2672. The four currents produced in the experimental 

 helix alternate by twos, i. e. those produced by the falling of 

 the first current in the core and the rising of the second and 

 contrary current, are in one direction. They occur at the 

 instant before and after the stop at the magnet, i. e. from the 

 moment of maximum current (in the core) before, to the 

 moment of maximum current after, the stop; and if that stop 

 is momentary, they exist only for that moment, and should 

 during that brief time be gathered up by the commutator. 

 Those produced in the experimental helix during the falling 

 of the second current in the core and the rising of a third 

 current (identical with the first) in the return of the core to 

 the magnet, are also the same in direction, and continue from 

 the beginning of the retreat to the end of the advance (or from 

 maximum to maximum) of the core currents, i. e. for almost 

 the whole of the core journey ; and these, by its change at 

 the maximum moments, the commutator should take up and 

 send on to the galvanometer. 



2673. The motion however of the core is not uniform in 

 velocity, and so sudden in its change of direction, but, as 

 before said (2665.), is at a maximum as respects velocity in 

 the middle of its approach to and retreat from the dominant 

 magnet ; and hence a very important advantage. For its stop 

 may be said to commence immediately after the occurrence of 

 the maximum velocity ; and if the lines of magnetic force were 

 equal in position and power there to what they are nearer to 

 the magnet, the contrary currents in the experimental helix 



