to Electricity and Magnetism. 

 Fig. 10. 



263 



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



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 ending cannot be distinguished from each 

 other, and we can only observe a single impulse, which, how- 

 ever, may be considered as the difference of two impulses in 

 opposite directions. 



91. The first experiment happened to be made with a cur- 

 rent 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 conclude, from this ex- 

 periment, that the currents of all orders are in the same di- 

 rection as that of the battery current, and I was the more 

 confirmed in this from the results of my first experiments on 

 the currents of ordinary electricity. The conclusion, how- 

 ever, caused me much useless labour and perplexity, and 

 was afterwards proved to be erroneous. 



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

 ference to each current, the important fact was discovered, 

 that there exists an alternation in the direction of the currents 

 of the several orders commencing with the secondary. This 

 result was so extraordinary, that it was thought necessary to 

 establish it by a variety of experiments. For this purpose 

 the direction was determined by decomposition, and also by 

 the galvanometer, but the result was still the same ; and at 

 this stage of the inquiry I was compelled to the conclusion 

 that the directions of the several currents were as follows : 



Primary current -f 



Secondary current -1- 



* It should be l-ecollected that all the inductions which have been men- 

 tioned 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 effects described. ^ 



