Supposed Polarity of Diamagnetic Bodies. 195 
r 
divided into four er the fo, the stop after it; the Jrom, and 
the stop succeeding that. a core of iron make this journey, _ 
its end towards the dominant magnet becomes a pole, rising in 
force until at the nearest distance, and falling in force until at the 
greatest distance. Both this effect and its progression inw 
* 
; the iron does not travel with a constant velocity ; for, bese of = 
: the communication of motion from a revolving crank at the ma- *, 
chine (2643.), it, in the to part of the journey, gradually rises | 
from a state of rest toa maximum velocity, which is half-way, 
and then as gradually sinks to rest again near the magnet :—and 
the from part of the journey undergoes the same variations. Now 
as the maximum effect upon the surrounding experimental helix 
depends upon the velocity pi nt with the intensity of the =. 
magnetic force in the end of the core, it is evident that it will” ‘sp 
not occur. with the maximum velocity, which is in the middle of. . 
the ¢o or from motion; nor at the stop nearest to the dominant 
| 
i 
where between the two. | Nevertheless, during the whole of the; 
advance, the core will cause a-current in the experimental helix... 
in one diteétion; and during the whole of the recession it gl * 
cause a current in the other direc tion.” ioe 
het nly 
ference being, that the two currents. peodtiged would Be i in thre’ rem = 
verse direction to those produced by iron, : Lae 
- 2667. Tt a commutator, therefore, were to be <a teapather? 
_Up these ae either in the one case or the other, “and sen * 
ethem on to the galvanometer in one consistent current, it. should’= . 
change at'the moments of th ! 2665.) ind fenywould ¢ | 
perform such.duty perfectly. If, the other hand, the commu; #3" 
_ tator, e% times of inaxi | : 
yettiose w 
k ed with! fegirod wire core, the ‘commutator chang- , 
9s (2665. . es ae current thered ‘up and sent 5 
