450 PROCEEDINGS OF THE AMERICAN ACADEMY 



angles to the bar, when, as should be the case, it was supported. The?e 

 results show, as we had expected, tliat parallel currents increase each 

 other, while opposite currents diminish each other. 



The experiment was repeated, approaching the armature with its 

 axis at right angles to the axis of the bar, when results similar to 

 those of Jamin were obtained. 



The delicacy of these experiments required a great number of 

 repetitions. This was done, and care was also taken to carefully 

 clean the armature each time lest any moisture from the hands, or 

 other foreign matter, should make it adhere to the bar. Chemically 

 pure iron was used to prevent the armatures acquiring a permanent 

 magnetism. 



I have thus attempted to show that the results of M. Jamin's experi- 

 ments, altliough undoubtedly correct, do not warrant the conclusions 

 respecting Ampere's theory which he has drawn, but, on the contrary^ 

 are a direct consequence of that theory : first, by investigating the con- 

 dition of the currents in the armature ; and, secondly, by showing that 

 contrary results are obtained by making the armature very long in 

 proportion to its diameter, and approaching it always with its longer 

 axis parallel to that of the bar. 



