110 Historical Sketch of FJeciro-magnetiim. "J Feb. 



nions, and contributo. to the advancement of this branch of science, 

 by something worthy of his great name. 



Among the names of those whom I have had occasion to note 

 at different times as occupied in endeavouring to give such an 

 account of the principles of electro-magnetic phenomena as 

 should form a correct theory, or at least such a statement of the 

 laws which oovern them as should account for the phenomena, is 

 that of Dr. Wollaston. 



Dr. Wollaston has not himself, that I know of, published any 

 thing; but a statement appeared in the Quarterly Journal of 

 Science, x. 363, which has his name to it, and is to be assumed, 

 therefore, as containing his opinions. The high value of this 

 philosopher's opinion is well known, and I should withhold a very 

 important part of this sketch, if I were not to copy all the Httle 

 that comes with such authority. 



** The phenomena exhibited by the electro-magnetic or con- 

 junctive wire may be explained upon the supposition of an elec- 

 tro-magnetic current passing round the axis of the conjunctive 

 ■wire, its direction depending upon that of the electric current, 

 or upon the poles of the battery with which it is connected. 



Dr. Wollaston. 



'* In the above figures, such a current is represented in two 

 sections at right angles to the axis of the wire, when similarly 

 electrified, from which it will be apparent that the north and 

 south povrci's meeting will attract each other. 



" In the following figures, the sections of the wire are shown 



dissimilarly electrified, by which similar magnetic powers meet, 

 and consequently occasion a repulsion." 



M. Schweiger, of Halle, has also proposed a theory which he 

 thinks more expl'.matory of the new phenomena than that of M. 

 Oersted. The latter indeed he opposes as insufficient to account 

 for many of the effects, and inconsistent with others. The only 

 account I have yet seen of M. Schweigger's theory is in the 

 Bibliotheque Universelle, March, 1821, p. 199, where it is stated 

 that to explain the phenomena, he supposes two magnetic axes 

 to exist in each transverse section of the conducting wire, the 

 axes being perpendicular to the direction of the cuiTent, and the 



