Masterpieces of Science 



covered by Oersted, in the winter of 1819-' 20. 

 It is illustrated by figure i, in which the mag- 

 netic needle is deflected by the action of a cur- 

 rent of galvanism transmitted through the wire 

 A B. 



B 



Fig. i 



The second fact of importance, discovered in 

 1820, by Arago and Davy, is illustrated in Fig. 2. 

 It consists in this, that while a current of gal- 

 vanism is passing through a copper wire A B, it 

 is magnetic, it attracts iron filings and not those 

 of copper or brass, and is capable of developing 

 magnetism in soft iron. 



Fig. 



The next important discovery, also made in 



1820, by Ampere, was that two wires through 



which galvanic currents are passing in the same 



direction attract, and in the opposite direction, 



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