24 



CONTRIBUTIONS TO ELECTRICITY AND MAGNETISM. 



cuit is broken by a cup of mercury, the rate of the diminution of the current, 

 within certain limits, remains the same, however the intensity of the electricity or 

 the length of the conductor may be varied. 







:Elq. dL8 

 3 ^ C 



V 





\ + 



A 



J> 



70. The several conditions of the foregoing examples are exhibited by the 

 parts of the curves, Figs. 18 and 19. The 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 AB and fall of CD, Fig. 18; 

 while, in the next Fig., (19,) the sudden rise of AB indicates the intensity 

 which produces the increased shock, after the number of elements of the bat- 

 tery has been increased. The accumulation of the electricity, which 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 bat- 

 tery, yet the needle of the galvanometer will be deflected only to the same 

 number of degrees, since the parts B c and ce give inductive actions in contrary 

 directions, and both within the time of a single swing of the needle, and, con- 

 sequently, will neutralize each other. The resulting deflecting force will, 

 therefore, be represented by ef, which is equal to Ck, or to bB, in Fig. 18. 



JTt^. 19 



A. hiU" 



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 

 the curve in each. 



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



