On Eledi^o- Dynamic Induction. 139 



nomena. And, first, however varied may be the intensity of the 

 induction expressed by the different parts of the two ends of the 

 curve, we may immediately infer that a galvanometer, placed in 

 the circuit of the secondary conductor, will be equally affected 

 at the beginning and ending of the primary current ; for, since 

 the deflection of this instrument is due to the whole amount of 

 a current, whatever may be its intensity, {57^) and since the or- 

 dinates cB and Cd are equal, which represent the quantity of in- 

 duction in the two directions, and, consequently, the amount of 

 the secondary current, therefore the deflection at the beginning 

 and ending of the battery current will, in all cases, be equal. 

 This inference is in strict accordance with the results of experi- 

 ment ; for, however rapidly or slowly we may plunge the battery 

 into the acid, and however irregular may be the rate at which it 

 is drawn out, still, if the whole effect be produced within the 

 time of one swing of the needle, the galvanometer is deflected to 

 an equal degree. 



66. Agahi, the intensity of one part of the inductive action, 

 for example that represented by A^, may be supposed to be so 

 great as to produce a secondary current capable of penetrating the 

 body, and of thus producing a shock* while the other parts of the 

 action, represented by ^B and CD, are so feeble as to affect the 

 galvanometer only. We would then have a result the same as 

 one of those given in the last section, (42,) and which was sup- 

 posed to be produced by two kinds of induction ; for if the shock 

 were referred to as the test of the existence of an induced cur- 

 rent, one would be found at the beginning only of the battery 

 current, while, if the galvanometer were consulted, we would 

 perceive the effects of a current as powerful at the ending as at 

 the beginning. 



67. The results mentioned in the last paragraph cannot be 

 obtained by plunging a battery into the acid ; the formation of 

 the current in this way is not sufficiently rapid to produce a shock. 

 The example was given to illustrate the manner in which the 

 same effect is supposed to be produced, in the case of the more 

 sudden formation of a current, by plunging one end of the conduc- 

 tor into a cup of mercury permanently attached to a battery already 



* The shock depends more on the intensity than on the quantity. See para- 

 graph 13. 



