ON ELECTRO-DYNAMIC INDUCTION. 



321 



79. The arrangement exhibited in Fig. 8 furnishes a ready means of 



Fig. 8. 



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



testing this. The primary current, as usual, is passed through coil No. 

 1, while coil No. 2 is placed over this to receive the induction, with 

 its ends joined to those of coil No. 3. By this disposition the secondary 

 current passes through No. 3 ; and since this is at a distance, and with- 

 out the influence of the primary, its separate induction will be rendered 

 manifest by the effects on helix No. 1. When the handles a, b are 

 grasped a powerful shock is received, proving the induction of a tertiary 

 current. 



80. By a similar but more extended arrangement, as shown in Fig. 

 9, shocks were received from currents of a fourth and fifth order ; and 

 with a more powerful primary current, and additional coils, a still 

 greater number of successive inductions might be obtained. 



81. The induction of currents of different orders, of sufficient inten- 

 sity to give shocks, could scarcely have been anticipated from our pre- 

 vious knowledge of the subject. The secondary current consists, as 

 it were, of a single wave of the natural electricity of the wire, dis- 

 turbed but for an instant by the induction of the primary ; yet this has 

 the power of inducing another current, but little inferior in energy to 

 itself, and thus produces effects apparently much greater in proportion 

 to the quantity of electricity in motion than the primary current. 



82. Some difference may be conceived to exist in the action of the 

 induced currents, and that from the battery, since they are apparently 

 different in nature ; the one consisting, as we may suppose, of a single 

 impulse, and the other of a succession of such impulses, or a continu- 

 ous action. It was therefore important to investigate the properties of 

 these currents, and to compare the results with those before obtained. 



83. First, in reference to the intensity, it was found that with the 



