On Electro-Dynamic Induction. 



229 



arrangement exhibited in Fig. 10. In this case 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 passing it 

 through a conductor of many spires. 



Fig. 10. 



a, c 



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



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

 currents, and this appeared important in connection with the na- 

 ture of the action. The experiments of Dr. Faraday would ren- 

 der 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 induc- 

 tive effects at the beginning and ending 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 nee- 

 dle it was found that this current was in the same direction with 

 the secondary and primary currents.* By a too hasty generaliza- 

 tion, I was led to conclude, from this experiment, that the currents 

 of all orders are in the same direction as that of the battery cur- 

 rent, and I was the more confirmed in this from the results of my 

 first experiments on the currents of ordinary electricity. This 

 conclusion, however, caused me much useless labor and perplex- 

 ity, and was afterwards proved to be erroneous. 



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

 to each current, the important fact was discovered, that there ex- 



* It should be recollected that all the inductions which have been mentioned, 

 were produced at the moment of breaking the circuit of the battery current. The 

 induction at the formation of the current is too feeble to produce the eifecta de- 

 scribed. 



