ON ELECTRO-DYNAMIC INDUCTION. 323 



Fig. 10. 



a coil No. 2, I helix No. 1, c coil No. 3, and d helix No, 2. 



helix No. 2, in the arrangement exhibited in Fig. 10. In this ease 

 the quantity of electricity in the current from the helix appears to be 

 too small to produce any effect, unless its power is multiplied by pass- 

 ing it through a conductor of many spires. 



90. The next inquiry was in reference to the direction of these cur- 

 rents, and this appeared important in connection with the nature of the 

 action. The experiments of Dr Faraday would render it probable, that 

 at the beginning and ending of the secondary current, its induction on 

 an adjacent wire is in contrary directions, as is shown to be the case 

 in the primary current. But the whole action of a secondary current 

 is so instantaneous, that the inductive effects at the beginning and end- 

 ing cannot be distinguished from each other, and we can only observe 

 a single impulse, which, however, may be considered as the difference 

 of two impulses in opposite directions. 



91. The first experiment happened to be made with a current of 

 the fourth order. The magnetizing spiral (11) was attached to the 

 ends of coil No. 4, Fig. 9, and by the polarity of the needle it was 

 found that this current was in the same direction with the secondary and 

 primary currents.* By a too hasty generalization, I was led to con- 

 clude, from this experiment, that the currents of all orders are in the 

 same direction as that of the battery current, and I was the more con- 

 firmed in this from the results of my first experiments on the currents 

 of ordinary electricity. The conclusion, however, caused me much 

 useless labour and perplexity, and was afterwards proved to be erro- 

 neous. 



92. By a careful repetition of the last experiment, in reference to 



* It should be recollected that all the inductions which have been mentioned were pro- 

 duced at the moment of breaking the circuit of the battery current. The induction at the for- 

 mation of the current is too feeble to produce the effects described. 

 VI. 4 F 



