240 Contributions to Electricity and Magnetism. 
ments of Wilson prove that the same effect is not produced with 
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, Fig. 14. 
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 
Fig. 14; the ends are shown bent 
back at a,a,a,a. In the popular experiment of the pierced card, 
es on each side appears to be due to an action of the same 
ind. 
a a «2D 
b glass 
plate; @, a, 4, 4, openings 
in tinfoil. 
127. It now appears probable, from the facts given in para 
gtaphs 119 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 ™ 
the direction of itself, and that the inverse influence takes placé 
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 - 
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 4 di- 
