OF ARTS AND SCIENCES. 



447 



and, since we know the positions of the poles of a magnet relatively to 

 a surrounding coil, we may determine the kind of magnetism, or, in 

 other words, the direction of the Amperian currents in either half of 

 llie bai*, which Jamiu's method fails to do. 



The results of this experiment, which are directly opposed to those 

 of Jamin, and, therefore, tend to confirm the theory of Ampere, are 

 given in the following table : — 



TABLE I. 



The first column gives the distances from the left end of the bar ; 

 column two gives the deflections of the galvanometer for parallel cur- 

 rents ; column three for opposed currents ; column four the calculated 

 means of column.s two and three ; column five the deflections due to a 

 sin<rle bobbin ; and column six the differences between columns four 



and five. 



A 470 



The equation to the curve of column six is 3/:= 73^ = .. > which is 



the same as the equation obtained by Jamin for the same case. 



From the above table it may be seen that, when currents are par- 

 allel, the deflection of the galvanometer is greater than when they are 

 opposed ; and, when the current is sent through a single bobbin, the 

 deflections are very nearly the means of the other two, as should be 

 the case if Ampere's theory were true. 



The conclusions which I have drawn are : — 



1°. Parallel currents add to each other. 



2°. Opposed currents diminish each other. 



3°. The action in the latter case oivAit to be nothing at the middle 



o O 



of the bar. Experiment shows this to be the case. 



