Electro-Magnetism, as a Moving Powe7\ 109 



powers be not more than sufficient to compensate for the loss ; 

 third, the power of a machine does not increase with its velocity^ 



The second general rule is, that integrity of the conducting 

 and magnetizing wires, is of the utmost consequence. By integ- 

 rity, I mean not only entire absence of flaws, fractures, and im- 

 perfectly soldered joints, but a perfect molecular arrangement. 

 Bending or twisting a wire, impairs its conducting power ; and a 

 wire which has once been wound upon a magnet, is not fit for 

 the same purpose again. 



Third. — It is well known that the repulsive power is not equal 

 to the attractive, of the same magnet, be it even of the hardest 

 steel. The difference between the two forces is still greater in 

 electro-magnets, and for the same reason. There is also another 

 cause which operates to diminish the repulsive forces of electro- 

 magnets, which will be considered when treating of the influence 

 of secondary currents. 



Fourth. — Two electro-magnets, unequally charged, attract each 

 other, even when similar poles are presented. The same is true 

 of the steel magnets, but not to so great an extent. 



Fifth. — Change of poles cannot be introduced in a machine, 

 for the following reasons: 1. It requires time; and during this 

 time, the magnets which change poles, are attracted and re- 

 tained somewhat by those which do not change. 2. Similar 

 poles will attract and produce back action ; for, unless the mag- 

 nets which change poles be favored by excess of battery, or 

 superior conductors, they cannot receive near the same charge, as 

 those which do not change : for, first, there is magnetism of an 

 opposite character to be overcome ; and secondly, two breaks in 

 the galvanic circuit are necessary to produce change of poles. 

 3. Two magnets which have a statical repelling power, that is, 

 a power which will merely keep them asunder when the machine 

 is at rest, will attract each other when the machine is in motion. 

 This singular fact is a consequence of secondary currents, shortly 

 to be described. 



The next law to be observed is, that the sum of the forces of 

 any number of magnets charged by one battery, is in a diminish- 

 ing ratio to the forces of one magnet charged by the same bat- 

 tery, provided the battery be not in excess. Hence there must 

 be a great loss of power, when a number of magnets are charged 



