110 Electro-Magnetism, as a Moving Poioer. 



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 or re- 

 cession of two charged magnets. These currents are found to 

 obey the following laws. 



The battery power remaining the same, the more coils sur- 

 rounding the magnet, the greater the power of the secondary cur- 

 rent. 



After one coil has been wound upon a magnet, the addition of 

 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 discoveries, when mag- 

 netism is developed in a bar of iron inclosed within a helix, a 

 secondary current flows in the helix contrary to the battery 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 toyvards 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 an 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 

 direction as the battery current. Therefore, an independent mo- 

 tion of an electro-magnetic machine diminishes the influence of 



