hy 'Electricity in Motion. 289 



Among the arrangements which he has thus formed, one of 

 the most remarkable consists in winding the conjunctive wire 

 around a cylinder of wood or glass, forming an elongated 

 spiral. Then the force emanating from each point of the 

 thread being always directed transversely to its length, becomes 

 in each element of the spiral, perpendicular to the plane of the 

 coils, and consequently parallel to the length of the spiral 

 itself. Farther, on account of the revolutive character of the 

 force, all the inner points of the different rings exercise, in the 

 interior of the spiral, forces which are equal, and operate in 

 the same direction; whilst in their action exteriorly, the forces 

 emanating from the different points of each ring, oppose and 

 weaken each other greatly by their obliquity. Thus the 

 result of all these actions ought to be much more energetic 

 within the spiral than outside of it ; a consequence which actu- 

 ally happens. If we place in the interior of a spiral, unmagnetic 

 steel needles, they will acquire in a few instants a per- 

 manent and very perceptible longitudinal magnetism; whereas, 

 if we place them without the spiral, they suffer no change. 

 This experiment is due to M. Arago. Sir H. Davy, without 

 being acquainted with it, has since succeeded in magnetizing 

 small steel needles, by rubbing them transversely on a single 

 conjunctive wire, or even without contact, by placing them at 

 some distance from it. This process does not differ from the 

 preceding, except in using the force of only one wire, a force 

 which the spiral multiplies. 



Since the electricity developed by the friction of our ordinary 

 machines, differs in no other respect from that evolved from 

 the voltaic apparatus, than that the former is retained and 

 fixed, while the latter is in motion ; we find that whenever we 

 cause the electricity of our machines to flow in a continuous 

 current, it has produced absolutely the same effects as the 

 voltaic battery. The similarity, or rather the identity, of these 

 two forms of electricity, is manifested likewise in the produc- 

 tion of the electro-magnetic phenomena. This has been shewn 

 by M. Arago, who transmitted along the spirals of M. Ampere, 

 no longer the voltaic current, but a succession of very small 



