1840] WRITINGS OF JOSEPH HENRY. 173 



short time A a, while the part g B denotes a more feeble 

 induction during the time represented by a c. In the same 

 way, by drawing up the battery suddenly at first, and after- 

 wards slowly, we may produce an inductive action such as 

 would be represented by the parts between C and D of the 

 ending of the curve. 



65. Having thus obtained representations of the different 

 elements of action, we are now prepared to apply these to the 

 phenomena. And first, however varied may be the inten- 

 sity 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 con- 

 ductor, 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 c B and 

 C d, which represent the quantity of induction in the two 

 directions, are equal, and consequently the amount of the 

 secondary current, therefore the deflection at the beginning 

 and ending of the batteiy 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 pro- 

 duced within the time of one swing of the needle, the gal- 

 vanometer 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 pene- 

 trating the body, and of thus producing a shock* while the 

 other parts of the action, represented hy g B and C D, are so 

 feeble as to effect the galvanometer only. We would then 

 have a result the same as one of those given in the last sec- 

 tion (42), and which was suppposed 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 



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

 paragraph 13. 



