by Electricity i?i Motion. 283 



mity be attached to the copper pole of the trough, the other 

 being fixed to the zinc pole. Imagine also that the person 

 who makes the experiment looks northward, and consequently 

 towards the copper or negative pole. In this position of things, 

 when the wire is placed above the needle, the north pole of 

 the magnet moves towards the west ; when the wire is placed 

 underneath, the north pole moves towards the east; and if 

 we carry the wire to the right or the left, the needle has no 

 longer any lateral deviation, but it loses its horizontality. If 

 the wire be placed to the right hand, the north pole rises ; to 

 the left, its north pole dips ; and in thus transporting the con- 

 junctive wire all around the needle, in directions parallel to 

 one another, we merely present it to the needle, by the different 

 sides of its circular contour, without affecting in the least the 

 proper tendency of the needle towards the terrestrial magnetic 

 poles. Since then the deviations observed in these successive 

 positions are first of all directed from right to left, when the 

 wire is above the needle ; then from above downwards, when 

 the wire is to the left ; from the left to the right, when the wire 

 is beneath ; and, finally, from below upwards, when it is to the 

 right hand, we must necessarily conclude from these effects, 

 that the wire deranges the needle, by a force emanating from 

 itself, a force directed transversely to the length of its axis, and 

 always parallel to the portion of its circular contour, to which the 

 needle is opposite. M. Oersted drew this inference from his 

 first observations. 



Now this revolutive character of the force, and revolutive 

 according to a determinate direction, in a medium which like 

 silver, copper, or other pure metal, seems perfectly identical in 

 all its parts, is a phenomenon very remarkable, of which we 

 had heretofore only one singular example in the deviations which 

 certain bodies impress on the planes of polarization of the lumi- 

 nous rays. The first fact of the magnetism transiently impressed 

 upon the conjunctive wire by the voltaic current, might have 

 oflfered itself to a vulgar observer. I do not know whether some 

 traces of this property "may not have been previously perceived 

 and indicated; but to have recognised this peculiar character of 



