292 TERRESTRIAL MAGNETISM.—MURPRHY. 
If two magnets similar to that at the figure be brought into 
proximity so that the poles of the same touch, they will repel 
each other; if, on the other hand, the north pole of one be 
approached to the south pole of the other, both bars, as if instinet 
with life, will fly in contact and cling one unto the other, and this 
intense affinity of opposite magnetisms is a general characteristic. 
The Magnetic Property is Molecular.—Apart altogether from 
the question as how we are to represent the action of a magnet 
upon other magnets, there arises another distinct question as to 
where the course of the action resides. A very old experiment 
at once throws considerable light on this point. If we break a 
bar magnet into two pieces, it will be found that each of these is 
itself a nagnet, its axis being in much the same direction as that 
of the original magnet, and its poles in corresponding positions. 
The same holds if we break the bar into any number of pieces, 
and, quite generally, if we remove any piece however small 
from a magnet, this piece will be found to be magnetic, the 
direction of its axis usually bearing a distinct and easily recogniz- 
able relation to the direction of the axis of the whole magnet. 
We are driven to the conclusion, therefore, that the magnetic 
quality of a body is related to its ultimate structure, and not 
simply to its mass as a whole, or to its surface alone, and this 
conclusion is not to be invalidated by the fact that we can in 
general, as will afterwards appear, represent the action of the 
inagnet at external points by means of a proper distribution 
of centres of attractive and repulsive forces upon its surface 
merely. We shall again refer to this property of the magnet. 
Temporary magnetism of soft iron and steel in the magnetic 
field.—Bodies which possess permanent magnetic properties not 
depending on the circumstances in which they are placed we 
shall call “ permanent magnets.” The law of the action of one 
permanent magnet on another, as we have seen, is that like poles 
repel and unlike poles attract each other. The action of a per- 
manent magnet on pieces of soft iron is, at first sight, different, 
for either pole attracts them alike. 
THE EKaArtH A MAGNET.—The earth has magnetic features 
entirely analagous to those of the bar marget. If we examine 
o 
