Miscellanies. 171 



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 jjIus, then the direction of the third 

 current will be minus, of the fourth cxuxeni 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 

 ordinary electricity. Shocks are obtained from these; the screening 

 influence of good conductors is shown to take place; magnetism is 

 developed ; and the alternations in the direction are found to exist as 

 in the currents from galvanic induction. Some remarkable results 

 are given in reference to the great distance at which the induction 

 takes place. Experiments are detailed in which needles were made 

 magnetic, when the conductors were removed to the distance of 

 twelve feet from each othei*. 



Prof. Henry made a verbal communication, during the course of 

 which he illustrated, experimentally, the phenomena developed in 

 his paper. 



November 16, 1838 — The Committee on the solar eclipse of the 

 18lh of September, made a further Report in part, comprising the fol- 

 lovi^ing observations : — 



