240 Contributions to Electricity and Magnetism. 



ments of Wilson prove that the same effect is not produced witll 

 an equal amount of electricity on the surface of a large conduc- 

 tor. It appears evidently therefore a case of the induction of an 

 electrical current on itself. The wire is charged with a consid- 

 erable quantity of feeble electricity, which passes off in the form 

 of a current along its whole length, and thus the induction takes 

 place at the end of the discharge, as in the case of a long wire 

 transmitting a current of galvanism. 



126. It is well known that the discharge from an electrical 

 battery possesses great divellent powers ; that it entirely separates, 

 in many instances, the particles of the body through which it 

 passes. This force acts, in part, at least, in the direction of the 

 line of the discharge, and appears to be analogous to the repulsive 

 action discovered by Ampere, in the consecutive parts of the same 

 galvanic current. To illustrate this, paste on a piece of glass a 

 narrow slip of tinfoil, cut it through at several points, and loosen 

 the ends from the glass at the places so cut. Pass a discharge 

 through the tinfoil from about nine half gallon jars ; the ends, at 

 each separation, will be thrown up, 

 and sometimes bent entirely back, 

 as if by the action of a strong, re- 

 pulsive force between them. This 

 will be understood by a reference to ,, „i^,„ „i,»„. „ „ 



•' b glass plate ; a, a, a, a, openings 



Fig. 14; the ends are shown bent in tinfoil. 



back at a, a, a, a. In the popular experiment of the pierced card, 



the bur on each side appears to be due to an action of the same 



kind. 



127. It now appears probable, from the facts given in para- 

 graphs 1 19 and 120, that the table in paragraph 92 is only an ap- 

 proximation to the truth, and that each current from galvanism, 

 as well as from electricity, first produces an inductive action in 

 the direction of itself, and that the inverse influence takes place 

 at a little distance from the wire. 



128. In reference to this view, the compound helix was placed 

 on coil No. 1, to receive the induction, and its ends joined to those 

 of the outer riband of tinfoil of the glass cylinder, while the 

 magnetizing spiral was attached to the ends of the inner riband- 

 A feeble tertiary current was produced by this arrangement, 

 which in two cases gave a polarity to the needle indicating a di- 



