n. THROUGH A CONDUCTING WIRE. 33 



exists a length of spark corresponding to a maximum 

 chemical action. 



Professor Seebeek of Berlin discovered that electii3 

 currents are produced by the partial application of heat 

 to a circuit formed of two solid conducting substances 

 as antimony and bismuth soldered together, another 

 proof of the correlation of heat and electricity. 



There cannot be a doubt that the atoms of a con- 

 ducting wire are in motion, and that they successively 

 take definite and momentary positions during the pas- 

 sage of an electric current, after which they return 

 successively to their normal state. When electricity is 

 invariably sent from the same pole of an inductive 

 apparatus through the wire of a telegraph, in a very 

 short time the wire is torn or divided into small sections, 

 which destroy its continuity ; but when the electricity 

 is sent from each pole alternately, the conducting wire 

 is not injured. As each atom of the wire has its own 

 electricity, this seems to indicate that during the suc- 

 cessive transits of the same kind of electricity, the pole 

 of each individual atom is attracted more and more in 

 the same direction, till at last they no longer return to 

 their normal state, the cohesive force is overcome, and 

 a rupture takes place, the more readily if there be any 

 imperfection in the wire. Since the electricity from 

 the other pole of the machine would have the same 

 effect, but in the contrary direction, an alternate 

 motion in the atoms must maintain the continuity of 

 the wire. 



A closed current of electricity or magnetism is accom- 

 panied by a simultaneous current of the opposite force 

 in the tangential direction equal in quality and inten- 

 sity. Thus the electric and magnetic currents, which 

 are merely transmissions of energy, differ by moving at 

 right angles to one another ; their effects are alike, yet 

 they are not identical. 



VOL. i. * D 



