1 822 .] Histonml Sketch of Electro-magnetism . 11 7 



in the Annales de Chiniie. I must again say, that having 

 assumed the existence of two distinct electric fluids, and the 

 identity of electricity with magnetism, I think the first part o€ 

 the theory by no means sufficiently developed. M. Oersted has, 

 in this respect, aimed at more perfection than M. Ampere ; with 

 what success, it is not necessary forme to determine. 



[To the historical sketch of electro-magnetism with which 1 

 have been favoured by my anonymous correspondent, I shall add 

 a sketch of the discoveries that have been made by Mr. Faraday, 

 of the Royal Institution ; the memoirs which contain the 

 account of these very important experiments are contained in 

 the 12th volume of the Quarterly Journal. — Ed.J 



Mr. Faraday's attention was first directed to the verificatioa 

 of the results obtained by previous experimenters as to the 

 attractions and repulsions of the needle by a connecting wire : 

 in attempting this, he ascertained that the position of the needle 

 with respect to the wire greatly modified the effects produced ; 

 he ascertained that the apparent attraction of the needle on one 

 side, and its consequent repulsion on the other, did not occur 

 under all circumstances, but that accordingly as the wire was 

 placed nearer to, or further from, the pivot of the needle, attrac- 

 tion or repulsion was produced on the same side of the wire : 

 this will, perhaps, be more clearly understood in the author's 

 own words : " If the wire be made to approach perpendicularly 

 towards one pole of the needle, the pole will pass off' on one side 

 in that direction which the attraction and repulsion at the 

 extreme point of the pole w^ould give ; but if the wire be conti- 

 lUially made to approach the centre of motion, by either the one 

 or the other side of the needle, the tendency to move in the 

 former direction diminishes ; it then becomes null, and the 

 needle is quite indifferent to the wire ; and ultimately the motion 

 is reversed, and the needle powerfully endeavours to pass the 

 opposite way." 



From the facts which have been now stated, Mr. Faraday 

 concludes, that the centre of magnetic action, or true pole of the 

 needle, is not placed at its extremity, but in its axis at a httle 

 distance from the extremity and towards the middle ; that this 

 point has a tendency to revolve round the wire, and necessarily, 

 therefore, the wire round the point; and as the same effects in 

 the opposite direction take place with the other pole, it is evi- 

 dent, in the opinion of Mr. F. that each pole had the power of 

 acting on the wire by itself, and not as any part of the needle, 

 or as connected with the opposite pole. The attractions and 

 repulsions he considers merely as exhibitions of the revolving 

 motion in different parts of the circle. 



It will not be necessary to follow Mr. Faraday through all the 

 difficulties which he had to contend with, or to describe every 



