ON MAGNETISM. 539 



so little understood as the theory of magnetism, we are obliged to admit 

 some paradoxical propositions, which are only surprising on account of 

 the imperfect state of our knowledge. Yet, little as we can understand 

 the intimate nature of magnetical actions, they exhibit to us a number 

 of extremely amusing as well as interesting phenomena ; and the prin- 

 ciples of crystallization, and even of vital growth and reproduction, are 

 no where so closely imitated, as in the arrangement of the small particles 

 of iron in the neighbourhood of a magnet, and in the production of a 

 multitude of complete magnets, from the influence of a parent of the 

 same kind. 



[Numerous and important as are the additions which have been recently 

 made to our knowledge of the agencies of electric and magnetic forces, our 

 limits will merely suffice us to mention those which appear to constitute 

 new and distinct branches of science. 



In 1819, Professor Oersted, of Copenhagen, discovered* that a current 

 of voltaic electricity exerts an action on the magnetic needle, which differs 

 in its character from the other forces observed in nature, inasmuch as it is 

 tangential to the course of the current. This will be best understood from 

 an inspection of the accompanying figures, in which N and S are the north 

 and south poles of Tin 



a magnet, cz is a c 

 wire, along which 

 flows a current of 

 voltaic electricity, 

 the end c being in 

 connexion with the 

 positive or copper 

 plate of the simple 

 battery, and the 



other end with the 



~"c 

 - negative or zinc 



plate. In figure 1, 

 where the wire is above the needle, it causes the north pole to be deflected 

 towards the east, as at n ; in figure 2, where it is below, towards the west. 

 Were the wire placed in the same horizontal plane with the needle, the 

 poles of the latter would simply suffer elevation or depression. The effect 

 of this force on the north pole of a magnet (that on the south pole being 

 of course the reverse) is represented by the following diagram, in which 

 the repulsion is in the 

 direction in which the 

 hands of the watch are ac- * *$ - 



customed to move. The 

 science which is built on 

 this fact is termed ELEC- 

 TRO-MAGNETISM. 



Fro,m the nature of the ^-j^^ 



* Thomson's Annals of Philosophy, 1820, xvi. 273. A.nn. de Ch. xxii. 201. 

 Schweigg. Jour, xxxii. 199 ; xxxiii. 123. 



