110 | Electro-Magnetism, as a Moving Power. 
by the same battery. The secondary current has also an impor- 
tant bearing upon this case. | 
One of the greatest obstacles we have yet to encounter, in the 
prosecution of this subject, is the influence of secondary currents 
to diminish the power of a machine, just in proportion to the use 
_ of those which at present we consider the most obvious means of 
increasing the power. By secondary currents are here meant, 
those currents which flow in the conducting wires, either with : 
or against the battery current, and are consequences of the devel- 
opment or cessation of magnetism, or of the approximation 
cession of two charged magnets, These currents are | 
obey the following laws. 
— one coil oe eco wound upon a magnet, the addition it 
a second coil increases the power of the secondary current in a 
greater ratio than the power of the magnet. Hence, as it has 
been found, some machines have had greater power with two 
coils of wire on the magnets than with four or five; although 
actual experiment proves, that the real or statical power of the 
magnets is considerably greater when a large number of coils is 
used. According to Faraday’s interesting Sem tists when mag- 
netism is developed in a bar of iron inclosed within a helix, a 
secondary current flows in the helix contrary to the Tccory cur- 
rent. When the magnetism ceases, the secondary flows in the 
same direction as the battery current. The development of mag- 
netism is equivalent to the determination or movement of mag- | 
netic forces towards the poles. The cessation of magnetic power 
is equivalent to the retreating of those forces. Now the ap- 
proximation of two electro-magnets attracting each other, occa- 
sions au additional movement or accumulation towards the poles, 
and consequently develops a secondary current flowing against 
the battery current. The power of this current is in proportion 
to the velocity with which the magnets approach each other. 
When two such magnets in proximity or contact are separated 
by mechanical force, a recession of accumulated forces takes place, 
and consequently a secondary is developed, flowing in the same 
as the at current. Therefore, an independent mo- 
c ine di the influence of 
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