i88a.] 
The Principles of Magnetism. 
25 
would probably arise. The tendency of every two contigu- 
ous magnets would still be to enter into astatic union, but 
this would be overbalanced by the sum of distant forces. 
Most probably the final relation would be that given above ; 
the central mass of magnets would control the axial positions 
of the surface magnets, and these exert a like influence 
upon the centre, while the isolated local influences would 
be overcome. Thus repulsive relations might exist between 
contiguous magnets, as a result of their attractive relations 
with masses of more remote magnets. 
For such relations to be assumed, of course the separate 
magnets must be free to revolve on their equatorial planes. 
But even where they have not this freedom of movement 
the vigour of this influence often shows itself by a reversal of 
the magnetism of some of the magnets. Such a reversal is 
stubbornly resisted, and the energy producing it must be 
considerable. We have instances of this result in the 
experiments of Coulomb and of Nobili. The former found 
on examining bundles of magnets that the exterior plates 
were the strongest, and that some in the interior had their 
magnetism reversed. Nobili experimented with bundles of 
fifty small needles which had been powerfully magnetised. 
On opening the bundles after a short time, all the magnetism 
continued in the same direction. But on opening again two 
hours afterwards, several of the needles were found to have 
reversed their magnetism. In another experiment, part of 
the needles lost their magnetism. In cases like this a 
general reversal could not well take place, for every magnet 
so reversed would exercise a counter force, and diminish the 
reversing influence upon the remaining magnets. And any 
vigour of retention of the original magnetism would also 
oppose the reversing agency. 
It may be supposed that the other relation of magnets 
alluded to — that of freedom to rotate and so change the 
direction of their axes — could not be produced in practice. 
Yet the practical existence of this relation may be found in 
every instance of magnetic energy. For it is well known 
that magnetism is not an energy belonging to masses as 
wholes, but that it belongs to their molecules or separate 
particles, and that what we call a magnet is really a com- 
pound mass of minute molecular magnets. In such an 
aggregate of minute magnets the conditions are different 
from those applying to masses of larger magnets. In the 
case of molecules there is no physical resistance to a change 
of the axial direction. They have no need to reverse their 
magnetism in response to the surrounding forces, for they 
