ELEMENTARY MAGNETISM. 275 
your magnet than to the other; the forces acting on the 
particle are no longer equal; the nearest pole of the 
magnet will act more powerfully on the particle than 
the more distant one. Let s N, fig. 12, be the magnet, 
and n the particle of north magnetism, in its new posi- 
tion. It is repelled by N, and attracted by s. Let the 
repulsion be represented in magnitude and direction by 
the line n o, and the attraction by the shorter line n m. 
The resultant of these two forces will be found by com- 
pleting the parallelogram m n op, and drawing its diagonal 
np. Along np, then, a particle of north magnetism 
would be urged by the simultaneous action of s and N. 
Substituting a particle of south magnetism for n, the same 
reasoning would lead to the conclusion that the particle 
would be urged along nq. If we place at n a short mag- 
netic needle, its north pole will be urged along n p, its 
south pole along n g, the only position possible to the 
S I.' 
FIG. 12. 
needle, thus acted on, being along the line p q, which is no 
longer parallel to the magnet. Verify this deduction by 
actual experiment. 
In this way we might go round the entire magnet; and, 
considering its two poles as two centers from which the 
force enamates, we could, in accordance with ordinary 
mechanical principles, assign a definite direction to the 
magnetic needle at every particular place. And substitut- 
ing, as before, a bit of iron wire for the magnetic needle, 
the positions of both will be the same. 
Now, I think, without further preface, you will be able 
to comprehend for yourselves, and explain to others, one of 
the most interesting effects in the whole domain of 
magnetism. Iron filings you know are particles of iron, 
irregular in shape, being longer in some directions than in 
others. For the present experiment, moreover, instead of 
