26 
ing the north poleof a magnet near ai piece of soft iron, the nearer 
end of the iron is of south polarity, and the farther of north. This 
is called induced magnetism, because the magnetism of the piece 
of soft iron is induced by the near presence of the permanent 
magnet. 
We can also have induced currents of electricity. If a wire 
through which an electric current is flowing be brought near a 
second wire, through the latter will also run a current, but in the 
opposite direction to the first, and only momentary. So long as 
the two wires are kept together, no further induced current will 
flow. But on withdrawing the wire connected with the battery, 
another induced current will flow through the other wire, again 
momentary, but this time in the opposite direction to the former 
one, and therefore in the same direction as the current from the 
battery. 
I will illustrate this by connecting this bobbin of wire with this 
delicate galvanometer, which consists simply of a small magnet 
placed in the ‘centre of a coil of wire. So sensitive is the magnetic 
needle in the galvanometer, that if a feeble current of Hlectricity 
be started round the coil, it will be defected. 
I connect another coil of wire with the battery, so that a strong 
electric current is sent through it; this one I shall rapidly insert 
in the bobbin, and the defection of the needle informs us that a 
current of Electricity has been induced in the wire round the 
bobbin; but only for a moment; the needle quickly resumes its 
original position, shewing that no more Electricity is flowing round 
it. 
Directly however I withdraw the coil, the defection of the needle 
again informs us that another induced current is started, but this 
time in the opposite direction to the first, as the needle moves in 
the opposite direction, So we can: have induced currents of Blec- 
tricity as well as induced magnetism. Perhaps this can be shown 
plainer by using the lantern galvanometer so that the movements 
of the needle can be thrown upon the screen. 
If, instead of a coil of wire being inserted in the bobbin, a 
permanent magnet be used, we have the same results. 
An electro-magnet may likewise be used. Over this powerful 
one which is connected with the galvanometer, I will rapidly bring 
down another electro-magnet, this one being connected with the 
battery, and we have the same approach causing deflection in one 
direction, and withdrawal in the opposite, and the currents only 
momentary. 
What I particularly wish to draw your attention to is, that these 
induced. currents are only momentary, and that the quicker ‘the 
approach;. orithe) witlidrawal, . theo greater: the deflection, proving 
