326 Prof. Oersted on Electro-magnetism. [Nov. 



effect of the other side of the needle may be immediately tried. It is 

 also easy to place S N horizontally, and to try the attraction or 

 repulsion exerted upon it by any given part of the connecting wire. 



Many ingenious attempts have been made to explain electro- 

 magnetic phenomena. The first which I am acquainted with is 

 that of my illustrious friend Berzelius. This philosopher sup- 

 poses, that the galvanic conductor possesses double transverse 

 magnetism, so that a conductor in the form of a parallelopiped 

 has a north magnetic pole at one of its angles, and a south at 

 the other. Let N S, N S, fig. 4 a, represent the transverse sec*- 

 tion of such a conductor placed in the magnetic meridian, and 

 receiving the current of electricity from the positive end of the 

 pile in the direction of south to north. The letters N N denote 

 the two north poles ; the letters S S the two south poles of the 

 conductor. This theory explains many of the phenomena satis- 

 factorily, and with surprising facility, as might naturally be 

 expected in the hypothesis of so distinguished a philosopher, but 

 it agrees nevertheless with only a part of the phenomena. The 

 observation which I have so frequently had occasion to make in 

 my experiments, that round conductors act in so equable a man- 

 ner in every part of the periphery, that no distribution of poles is 

 discoverable in them, excited some suspicions against this 

 new hypothesis, and a direct experiment decided me absolutely 

 against it. Twist a steel wire round one half of a square conductor, 

 in such a manner that it may coincide with the semiperiphery 

 NSN, or 8 N S, on which side soever it may be ; according to 

 the hypothesis, this wire ought to have either no magnetism at 

 all, or equal poles at the two ends ; but it will be found that the 

 wire has always a north pole at that point towards which — s is 

 directed, and a south pole at the point to which + s is directed. 

 These directions will be explained in fig. 4. 



As in these experiments very fine wire only should be used, a 

 weak needle should also be employed : a small piece of the same 

 iron wire fastened to a bit of raw silk is extremely convenient. 

 In general, a steel wire may be magnetized by placing it across 

 the conductor, although the latter be a parallelopiped, round or 

 flat, and the wire may occupy a great or small part of the peri- 

 phery; the point towards which — s turns always gains the 

 property of turning towards the north. What is also remarkable 

 is, that the magnetic pole produced in the steel wire applied to 

 the conductor, is of the same kind as the pole of a neighbouring 

 magnet repelled in the same direction. This proves also that 

 the conductor cannot be considered as a body which has distin- 

 guishable poles on the surface ; for in this case the poles pro- 

 duced and repelled would be of the same denomination. 



In order to answer the question, whether the wire attached to 

 the surface of the conductor might be considered as a part of 

 that surface, differing only from others in itspowerof retainingthe 

 magnetism communicated, I put a piece of fine paper between 

 the conductor and the steel wiFe : in other respects I performed 



