594 SPECIAL METHODS OF DISCOVERT. 



tested it by further experiments, proved it, and made 

 the discovery. By reasoning upon all the results, and 

 basing calculations upon them, he reduced to a simple and 

 extensive mathematical theory, all the new and complex 

 facts of electro-magnetism almost as soon as they were 

 published. His theory not only explained known facts, 

 but enabled new cases to be deductively inferred and 

 predicted, and these also were soon confirmed by experi- 

 ment ; it included also the mutual actions of magnets 

 as well as of conductors. He termed the phenomena 

 ' electro-dynamic ' ; and he published his views on Sep- 

 tember 18, 1820, before the French Academy of Sciences 

 only about two months after Oersted's discovery was first 

 made known in Paris. His theory was that an electric 

 current circulates round each particle of a magnet. 

 Faraday, by studying the phenomena of electro-mag- 

 netism, and the mutual relation of forces, was led to infer 

 that as an electric current produced magnetism, so mag- 

 netism might be caused to produce electric currents ; and 

 in the year 1831, by devising a suitable experiment of 

 introducing a bar-magnet into a coil of insulated copper 

 wire, and then withdrawing the magnet whilst the two 

 ends of the wire were connected with a distant galvano- 

 meter, he succeeded in proving his inference and making 

 the discovery. Seebeck, in 1823, inferred the hypothesis 

 that heat might be caused to produce electricity, and 

 devised an experiment for the purpose. He joined together 

 the ends of two bars of copper and antimony so as to form 

 a kind of circle or stirrup. In this he suspended deli- 

 cately a magnetised needle, and then heated one of the 

 junctions of the dissimilar metals. The needle moved by 

 the influence of the current thus produced, and the dis- 

 covery was made. The eminent philosopher, Gauss, by 

 studying the various facts at his command, inferred his 



