83.2 



miles. 



Near the battery .... 33| 



110 31 



220 25 



330 15 



440 12 



550 5 



660 



The deflections of the needle of the galvanometer employed in 

 these experiments were, when they did not surpass 36, very nearly 

 comparable with the force of the current. This I ascertained in the 

 following way. I took six cells of the small constant battery de- 

 scribed in my paper " On new Instruments and Processes for deter- 

 mining the Constants of a Voltaic Circuit," printed in the Philo- 

 sophical Transactions for 1843, and placed in the circuit formed of 

 the 660 miles of wire, the earth, and the galvanometer, successively 

 1, 2, 3, 4, 5 and 6 cells. Leaving out of consideration the resist- 

 ances in the cells themselves and in the earth, which were very in- 

 considerable in comparison with that in the long wire, the force of 

 the current should be approximately proportionate to the number 

 of the elements ; and since the deflections of the needle nearly indi- 

 cated this proportionality, as the following table will show, it may 

 be assumed that the force of the current, when the deflection of the 

 needle did not surpass 36, nearly corresponded with the angular 



deviation. 



cell. 



1 6 



2 14 



3 19 



4 28 



5 32 



6 36 



From the preceding experiments (6. and 7.) it seems to result, 

 that whatever length of wire is connected with the battery, if a gal- 

 vanometer is placed at the farther extremity of the wire and a con- 

 stant length added to the other termination of the galvanometer, its 

 indication remains always nearly the same. Thus the galvanometer 

 indicated e^when it was placed close to the battery and 110 miles 



