276 LOCALIZED ELECTRIZATION. 



tion acts as a second initial source, nearly in the same manner as 

 the battery, upon the wire of the primary coil, the current of 

 which it reinforces, and which, in its turn, reacts upon the current 

 of the secondary coil, so that the power of this last current is pro- 

 portionately increased. In the magneto-faradic instruments, the 

 initial force is more simple ; it is the intermittent changes in the 

 state of the fixed magnet which produce induction in the wire 

 coiled immediately around it. But the power of this induction is 

 very feeble, if exerted by that influence alone, or, in other words, 

 only by the rotary movements of the armature. In order that the 

 induction should acquire power, it is necessary that the solutions 

 of contact should take place in the wire of the coil, at the moment 

 when the modifications of the magnet are at their maximum (a 

 little before the contact reaches the vertical or horizontal position). 

 Such are the arrangements of the primary coil of my magneto- 

 faradic apparatus ; the solutions of contact, which are produced by 

 the rheotome, occur only in the thick wire which immediately 

 surrounds the fixed magnet ; the long fine wire, which is rolled 

 round the thick wire, has no communication with the rheotome. 

 If we suppress, in the thick wire, the solutions of contact produced 

 by the rheotome, the current in the fine wire of the outer coil 

 immediately becomes extremely weak, just as if we produced, by 

 the same rheotome, solutions of contact in the fine wire. The 

 intensity of the current of the last then increases a little, but 

 ' remains very feeble, as compared with that which is developed 

 when the solutions of contact occur in the thick wire. The 

 following is the proof : — 



Experiment. — The power of tbe current develoiied in the firie wire of my 

 magneto-faradic apparatiis is considerable. But if the solutions of contact of 

 the wii'e of the primary coil, produced by the rheotome, are suspended (which 

 may be effected in my instrument by tui-ning the knob Q, tig. 64, from right to 

 left), that is to say, when the cmi-ent formed by the wire of the primary coil 

 remains interrupted, the power of the current of the secondary coil is so 

 diminished that it can scarcely be felt, even by placing the rheophores upon 

 the lips. Even when the solutions of contact are produced by the rheotome 

 in the wire of the secondary coil itself — an effect which I have obtained by a 

 simple mechanism, in an apparatus constructed purposely for these experi- 

 ments — its current is still infinitely more feeble than when the same coil is 

 induced by the primary one. 



I have thought, and the idea has, without doubt, presented itself 

 to the minds of my critics, although they have Jiot succeeded in 

 expressing it very clearly,''' that possibly my primary coil acted 



7 I here qixote, precisely, the criticism properties of its two coils: "In the mag- 



which one ol' my learned opiionents, M. neto-electric apparatus of M. Duchenue," 



A. Becquerel, has bestowed upon my lie says, " two wires are coiled, one over 



magneto-faradic instrument, and upon the the other, around a fixed magnet, the first 



