MAGNETIC CONDUCTION — CONDUCTION POLARITY. 
35 
2819. Taking the simplest case of paramagnetic polarity, or that presented in fig. I 
(2807.), it consists in a convergence of the lines of magnetic force on to two opposed 
parts of the body, which are to each other in the direction of the magnetic axis. The 
difference in character of the two poles at these parts is very great, being that which 
is due to the known difference of quality in the two opposite directions of the line of 
magnetic force. Whether polar attraction or repulsion exists amongst paramagnetic 
bodies, when they present mere cases of conduction (as oxygen, for instance), is not 
yet certain (2827,), but it probably does ; and if so, will doubtless be consistent with 
the attraction and repulsion of magnets having correspondent poles. 
2820. When we consider the conduction polarity of a diamagnetic body, matters 
appear altogether different. It has not a polarity like that of a paramagnetic sub- 
stance, or one the mere reverse (in name or direction of the lines of force) of such a 
substance, as I, Weber and others have at times assumed (2640.), but a state of its 
own altogether special. Its polarity consists of a divergence of the lines of power on to, 
or a convergence from the parts, which being opposite, are in the direction of the mag- 
netic axis ; so that these poles, having the same general and opposite relations to each 
other, which correspond to the differences in the poles of paramagnetic bodies, have 
still, under the circumstances, that striking contrast and difference from the polarity of 
the latter bodies which is given by convergence and divergence of the lines of force. 
2821. Let fig. 3 represent a limited mag- 
netic field with a paramagnetic body P, and a 
diamagnetic body, D, in it, and let N and S 
represent the two walls of iron associated with 
the magnet (2465.) which form its boundary, 
we shall then be able to obtain a clear idea 
of the direction of the lines of magnetic force in the field. Now the two bodies, P and 
D, cannot be represented by supposing merely that they have the same polarities in 
opposite directions. The 1 polarity of P is importantly unlike the 3 polarity of D ; 
but if D be considered as having the reverse polarities of P, then the 1 polarity of P 
should be like the 4 polarity of D, whereas it is more unlike to that than to the 
3 polarity of D, or even to its own 2 polarity. 
2822. There are therefore two essential differences in the nature of the polarities 
dependent on conduction, the difference in the direction of the lines of force abutting 
on the polar surfaces, when the comparison is with a magnet reversed, and the dif- 
ference of convergence and divergence of these lines, when compared with a magnet 
not reversed ; and hence a diamagnetic body is not in that condition of polarity which 
may be represented by turning a paramagnetic body end for end, while it retains its 
magnetic state. 
2823. Diamagnetic bodies in media more diamagnetic than themselves, would 
have the polar condition of paramagnetic bodies (2819.) ; and in like manner para- 
magnetie conductors in media more paramagnetic than themselves, would have the 
polarity of diamagnetic bodies. 
F 2 
Fig. 3. 
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