to Electricity and Magnetism. 489 



breaking of the circuit, In this experiment, did not appear af- 

 fected by joining or separating the ends of coil No. 4. 



20. Having investigated the conditions on which the induc- 

 tive action at the beginning of a battery current depends, 

 experiments were next instituted to determine the nature of the 

 effects produced by this induction : and first the coils were 

 arranged in the manner described in my last paper (III. 79.), 

 for producing currents of the different orders. The result 

 with this arrangement was similar to that which I have de- 

 scribed in reference to the ending induction, namely, currents 

 of the third, fourth, and fifth orders were readily obtained. 



21. Also, when an arrangement of apparatus was made si- 

 milar to that described in paragraph 87 of my last paper, it 

 was found that a current of intensity conld be induced from 

 one of quantity and the converse. 



22. Likewise, the same screening or rather neutralizing 

 effect was produced, when a plate of metal was interposed 

 between two consecutive conductors of the series of currents, 

 as was described (III. Section IV.) in reference to the ending 

 induction. In short, the series of induced currents produced 

 at the beginning of the primary current appeared to possess 

 all the properties belonging to those of the induction at the 

 ending of the same current. 



23. I may mention, in this place, that I have found, in the 

 course of these experiments, that the neutralizing power of a 

 plate of metal depends, in some measure, on its superficial 

 extent. Thus a broad plate which extends, in every direc- 

 tion, beyond the helix and coil, produces a more perfect 

 screening than one of the same metal and of the same thick- 

 ness, but of a diameter only a little greater than that of the coil. 



24. The next step in the investigation was to determine the 

 direction of the currents of the different orders produced by 

 the beginning induction, and fortius purpose the magnetizing 

 spirals (5.) were used, and the results obtained by these veri- 

 fied by the indications of the galvanometer. It shotild be 

 stated here, as a fact which was afterwards found of some im- 

 portance, that although the needle of the galvanometer was 

 powerfully deffected when the instrument was placed in the 

 circuit of the secondary current, yet a very feeble eflect was 

 produced on it by the action of a current of the third, fourth 

 or fifth order. The directions, however, of these current, as 

 indicated by the feeble motion of the needle, were the same 

 as those given by the magnetizing spiral, 



25. The direction of the different currents jiroduced at the 

 making of the battery current, as determined by these instru- 

 ments, is as follows : namely, the direction of the secondary 



