22 CONTRIBUTIONS TO ELECTRICITY AND MAGNETISM. 



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 ordinates cB and Cd are equal, which 

 represent the quantity of induction in the two directions, and, consequently, 

 the amount of the secondary current, therefore the deflection at the begin- 

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

 inference is in strict accordance with the results of experiment; 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. Again, the intensity of one part of the inductive action, for example that 

 represented by A g, 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 supposed to be produced 

 by two kinds of induction; for if the shock were referred to as the test of the 

 existence of an induced current, one would be found at the beginning only of 

 the battery current, while, if the galvanometer were consulted, we would per- 

 ceive 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 sufliciently 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 con- 

 ductor into a cup of mercury permanently attached to a battery already in the 

 acid, and in full operation. The current, in this case, rapid as may be its de- 

 velopment, cannot be supposed to assume per saltum its maximum state of 

 quantity ; on the contrary, from the general law of continuity we would infer, 

 that it passes through all the intermediate states of quantity, from that of no 

 current, if the expression may be allowed, to one of full development; there 

 are, however, considerations of an experimental nature which would lead us 



* The shock depends more on the intensity than on the quantity. See paragraph 13. 



