g||2 . Mistorical Sketch of Electro-mas^netiim . [Fe b . 



^Hftltaic battery, being a conductor of electricity, it carries off the 



^llpro fluids ; but the battery having within itself the power of 

 continually conveying fresh portions of the fluids to the two 

 extremities, the first portions that are removed by the wire are 

 succeeded by others, and thus currents are produced, which are 

 constant as long as the battery remains in action, and the poles 

 continue connected by the wire. Now as it is in this state that 

 .tlie wire is capable of affecting the magnetic needle, it is very 

 important for the exact comprehension of the theory that a clear 

 and precise idea of its state, or of what is assumed to be Us 



relate, should be gained, for on it in fact the whole of the theory 

 .is founded. Portions of matter in the same state as this wire, 



/may be said to constitute the materials from which M. Ampere 

 vibrms, theoretically, not only bar magnets, but even the great 



. magnet of the earth ; and we may, therefore, be allowed to 

 expect that a very clear description will first be offered of it. 

 This, however, is not the case, and is, I think, very much to be 

 regretted, since it renders the rest of the theory considerably 

 obscure, for though certainly the highly interesting facts disco- 

 vered by M. Ampere could have been described, and the general 

 »laws and arrangements both in conductors and magnets stated 

 with equal force and effect without any reference to the internal 

 state of the wire, but only to the powers which experiment 

 proves it to be endowed with, yet as M. Ampere has chosen 

 always to refer to the currents in the wire, and in fact founds 

 his theory upon their existence, it became necessary that a cur- 



jreiit should be described. 



At p. 63, vol. XV. Annales de Chimie, M. Ampere, while 



. -^peaking of the battery and connecting wire, says, it is generally 

 agreed that the battery continues to convey the two electricities 

 ia the two directions it did at the moment the connexion was 

 rfirst completed ; ** so that a double current results, the one of 

 piositive electricity, the other of negative electricity, parting in 

 ^t)pposite directions from the points where the electro-motire 

 .action exists, and reuniting in that part of the circuit opposed 

 to those points.*^ This reunion would, of course, take place. in 

 the wire, and one may be allowed to ask, whether the magnetic 

 effects depend on it, as M. Oersted seems to think, who calls it 

 the electric conflict, and also what becomes of the electricities 

 that accumulate in the wire. But from other parts of M. 

 Ampere's memoirs, a very different idea of the electric currents 

 jg^y be gained; the one electricity is considered as continually 

 circulating in one direction ; while the other electricity circu- 

 iales and moves in a current in the opposite directiot;, so that 



^e two electricities are passing by each other in opposite direc- 

 «lioQS in the same wire and apparatus. 



Without, however, dwelling on the state of the wire when 

 thus circumstanced, M. Ampere is content, in order to avoid 

 confusion, when speaking of the direction of the electrical cur- 



4itnts. to wave attention to the two, and to speak as if there 



