amp6re 229 



the electrostatic forces, which the electricities in the wires 

 would exert upon one another when at rest. Ampere car- 

 ried out these experiments also with wires bent into a circular 

 form, and with coils consisting of many circular windings, 

 through which he passed current. In this way coils (called 

 by Ampere 'solenoids') came into use, though these had 

 already, shortly before, appeared in the 'multiplier.' Am- 

 pere also showed that Newton's law of reaction also holds for 

 the newly discovered force as well as for the forces discovered 

 by Oersted, so that the current-carrying conductor is able to 

 set the magnet in motion, and conversely the magnet the 

 conductor. 



The discovery of the forces between current and current 

 immediately led Ampere further to a peculiar conception of 

 magnetism. He regarded a magnetised rod as a coil carry- 

 ing a current, a current which flows by itself uninterruptedly. 

 He was actually able to show that two coils, one of which is 

 movable, deflect one another, and act upon one another 

 with their ends, in exactly the same way as do two mag- 

 netised rods with their poles. Indeed he was even able to 

 show that a single circular current, when suspended so as to 

 be free to move, sets itself like a magnetic needle with refer- 

 ence to the earth's magnetism. In this way all magnetic 

 forces could be referred to the forces between current and 

 current; and magnetism ceased to be a thing by itself. This 

 was entirely in accordance with reality, inasmuch as it was 

 already clear since Gilbert's experiments with broken mag- 

 nets, that in actual fact there is nothing peculiar about mag- 

 netic poles, but that we have in a magnetised rod a state 

 uniformly distributed and directed. 



According to Ampere, every magnet could be imagined as 

 composed of circular currents similar in direction and set 

 side by side, and could actually be completely substituted 

 in all eflFects of its forces by such a circular current. In the 

 last resort it was only necessary to assume that every iron or 



