55 



The first section of the paper refers to the conditions which infill* 

 ence the induction of a current on itself, as in the case of a long 

 wire and a spiral conductor. These are shown to depend on the 

 intensity and quantity of the battery current, and on the length, thick- 

 ness, and form of the conductor. 



The next section examines the conditions necessary to the produc- 

 tion of powerful secondary currents, and also the changes which take 

 place in the same, when the form of the battery, and the size and form 

 of the conductor are varied. The important fact is shown, that not 

 only a current of intensity can be induced by one of quantity, but 

 also the converse, that a current of quantity can be produced by one 

 of intensity. 



The third section relates to the effect of interposing different sub- 

 stances between the conductor which transmits the current from the 

 battery, and that which is arranged to receive the induced current. 

 All good conducting substances are found to screen the inducing ac- 

 tion, and this screening effect is shown, by the detail of a variety of 

 experiments, to be the result of the neutralizing action of a current, 

 induced in the interposed body. This neutralizing current is sepa- 

 rately examined, and its direction found to be the same as that of the 

 battery current. The question is then raised, how two currents in 

 the same direction can counteract each other? An answer to this 

 question is given in a subsequent part of the paper. 



The fourth section relates to the discovery of induced currents of 

 the third, fourth, and fifth orders; — that is, to the fact that the second 

 current is found capable of inducing a third current, and this latter 

 again another, and so on. The properties of these new currents are 

 next examined, and the screening influence is found to take place be- 

 tween them; quantity is induced from intensity, and conversely; 

 magnetism is developed in soft iron; decomposition is effected, and 

 intense shocks are obtained, even from the current of the fourth or- 

 der. A remarkable and important fact is stated in reference to the 

 direction of these currents. If the direction of the battery current 

 and that of the second be called plus, then the direction of the third 

 current will be minus, of the fourth current plus, of the fifth minus, 

 and so on. The application of the fact of these alternations is made 

 to the explanation of the phenomenon of screening before mentioned, 

 and also to the improvement of the magneto-electrical machine. 



The last part of the paper relates to the discovery of secondary 

 currents, and of currents of the several orders, in the discharge of 



