ADDRESS OF PROF. A. M. MAYER. 477 



About 1820, men of science spoke of electrical knowledge as 

 almost complete. The mathematical consequences of the laws dis- 

 covered by Coulomb and others having been, they thought, fully 

 developed; electricity was hardly to be regarded as an experi- 

 mental science, but henceforth might be grouped with mechanics. 

 Such opinion was so general that Faraday (in 1831), when he began 

 his ever remarkable series of discoveries, was influenced by this 

 prevailing feeling to style his papers "Experimental Researches in 

 Electricity." 



It seemed almost impossible that any discovery could again give 

 an impulse to electrical studies equal to that produced by the bril- 

 liant and most fertile researches of Volta; yet to the universal 

 surprise of the scientific world this happened. In the winter of 

 1819 Oersted announced that he had at last discovered a correlation 

 of actions between electricity and magnetism in his celebrated 

 experiment of the deflection of a magnet athwart the conjunctive 

 wire of a battery when the latter was laid parallel to the direction 

 of the magnet. 



During the month of July, 1820, the news of Oersted's discovery 

 reached Paris. It at once excited profoundly the ever active and 

 versatile mind of Ampere. This man, already celebrated as a 

 mathematician, was now destined to show greater genius as an 

 experimenter. He at once began a series of researches in the field 

 opened by the discovery of Oersted ; and with astonishing rapidity 

 reached results of such importance that they gained him the title 

 of the Newton of electro-dynamics; and justly, for he did for this 

 branch of science even more than Coulomb had previously done 

 for electro-statics. 



On the 1 8th of September, 1820, Ampere read before the Academy 

 of Sciences of Paris his first paper on electro-dynamics. In this 

 he shows that the battery exerts an electro-magnetic action as well 

 as its conjunctive wire, and he gives a rule by which one can readily 

 predict the direction in which a magnet will be deflected by a voltaic 

 current. He supposes a current to flow from the copper to the 

 zinc plate of the battery; then, says he, if you imagine yourself at 

 full length and facing the wire, the current entering your heels and 

 passing out at your head, the north pole of the magnet is always 



