On Electro- Dynamic Induction. 151 



be supposed to be more rapid at the first moment, than after 

 it has lost somewhat of its intensity, or sunk more nearly to its 

 normal state. These variations are indicated by the rapid rise of 

 the curve, Fig. 17, from A to g, and the more gradual increase of 

 the ordinates from A to B ; and by the rapid diminution of the 

 ordinates between C and Z, and the gradual decrease of those to- 

 wards the end of the curve. 



89. These more minute considerations, relative to the form of 

 the curve, will enable us to conceive, how the time of the end- 

 ing of the secondary current, as we have suggested, (78,) may 

 be prolonged beyond that of the natural subsidence of the dis- 

 turbance of the electricity of the conductor on which this current 

 depends. If the development of the primary current is produ- 

 ced by equal increments in equal times, as would be the case in 

 plunging the battery (59) into the acid with a uniform velocity ; 

 then the part AB of the curve Fig. 17, would be a straight line, 

 and the resulting secondary current, after the first instant, would 

 be one of constant quantity during nearly the whole time repre- 

 sented by Ac; but if the rate of the development of the primary 

 current be supposed to vary in accordance with the views we 

 have given in the last paragraph, then the quantity of the secon- 

 dary current will begin to decline before the termination of the 

 induction, or as soon as the increments of the primary begin to 

 diminish ; and hence the whole time of the subsidence of the 

 secondary will be prolonged, or the length of hC, Fig. 20, will 

 be increased, the descent of BC be more gradual, and the inten- 

 sity of the ending induction of the secondary current be dimin- 

 ished: (see last part of paragraph 78.) 



90. Besides the considerations we have mentioned, (88,) there 

 are others of a more obvious character, which would also appear 

 to affect the form of particular parts of the curve. And first we 

 might perhaps make a slight correction in the drawing of Figs. 

 17, 18, &c., at the point A, in consideration of the fact that the 

 very first contact of the end of the conductor with the surface of 

 the mercury is formed by a point of the metal, and hence the 

 increment of development should be a little less rapid at the first 

 moment than after the contact has become larger ; or in other 

 words, the curve should perhaps start a little less abruptly from 

 the axis at the point A. Also Dr. Page has stated* that he finds 



Vide this Journal, Vol. xxxiv, p. 166. 



