504 Prof. J. Henry's Contributions 



gradual development of the current in the short conductor, 

 with a single battery, and the gradual decline of the same, 

 are represented by the gentle rise of A B and iall of C D, 

 fig. 18; while, in the next fig, (19.)> ^^^^ sudden rise oi' A B 

 indicates the intensity which produces the increased shock, 

 after the number of elements of the battery has been increased. 

 The accumulation of the electricity, whicii almost instantly 

 subsides, is represented by the part Bee, fig. 19; and from 

 this we see, at once, that although the shock is increased by 

 using the compound battery, yet the needle of the galvano- 

 meter will be deflected only to the same number of degrees, 

 since the parts Be and ce give inductive actions in contrary 

 directions, and both within the time of a single swing of the 

 needle, and, consequently, will neutralize each other. The 

 resulting deflecting force will, therefore, be represented by 

 ej] which is equal to C/i', or to b B, in fig. 18. 



c Fig. 19. 



The intensity of the shock at the breaking is represented 

 as being the same in the two figures, by the similarity of the 

 rate of descent of the part C D of thecurve in each. 



71. We have said (69.) that the quantity of current elec- 

 tricity in a short conductor and a compound battery, after the 

 first discharge, is nearly the same as with a single battery. 

 The exact quantity, according to the theory of Ohm, in a 

 unit of length of the conductor, is given by the formula 



n A 



?• ?j + R ■ 



In this n represents the number of elements; A, the elec- 

 tromotive force of one element; ?•, the resistance to conduc- 

 tion of one element; and R, the length of the conductor, or 

 rather its resistance to conduction in terms of /•. Now, when 

 R is very small, in reference to r n, as is the case wilh a very 

 short metallic conductor, it may be neglected, and then the 

 expression becomes 



n K A 



or — ; 



r n r 



and since this expresses the quantity of current electricity in 

 a unit of the length of the circuit, with either a single or a 

 compound battery, therefore, wilh a short conductor, the quan- 

 tity of current electricity in the two cases is nearly the same. 



