350 NOTICES OF THE MEETINGS [Jan. 20, 
through a will deflect it in. the reverse direction ; so that currents 
will flow out of both extremities of the wire in opposite directions, 
whilst no current is going into it from any source. Or if a be 
quickly put to the battery and then to the earth, it will shew a 
current first entering into the wire, and then returning out of the 
wire at the same place; no sensible part of it ever travelling on 
to 6 or e. 
When an air wire of equal extent is experimented with in like 
manner, no such effects as these are perceived: or if, guided by 
principle, the arrangements are such as to be searching, they are 
perceived only in a very slight degree, and disappear in comparison 
with the former gross results. The effect at the end of the very 
long air wire (or c) is in the smallest degree behind the effect at gal- 
vanometer a; and the accumulation of a charge in the wire is 
not sensible, 
All these results as to dime, &c. evidently depend upon the same 
condition as that which produced, the former effect of static charge, 
namely, lateral induction; and are necessary consequences of the 
principles of conduction, insulation, and induction, three terms 
which in their meaning are inseparable from each other (Exp. Res. 
1320, 1326,* 1338, 1561, &c.). If we put a plate of shell lac upon 
a gold leaf electrometer and a charged carrier (an insulated metal 
ball of two or three inches diameter) upon it, the electrometer is 
diverged ; removing the carrier, this divergence instantly falls, this 
is insulation and induction: if we replace the shell lac by metal, the 
carrier causes the leaves to diverge as before, but when removed, 
though after the shortest possible contact, the electroscope is left 
diverged, this is conduction. If we employ a plate of spermaceti 
instead of the metal, and repeat the experiment, we find the diver- 
gence partly falls and partly remains, because the spermaceti insu- 
lates and also conducts, doing both imperfectly: but the shell lac 
also conducts, as is shewn if time be allowed; and the metal also 
obstructs conduction, and therefore insulates, as is shewn by simple 
arrangements. For if a copper wire, 74 feet in length and +; of 
* 1326. All these considerations impress my mind strongly with the con- 
viction, that insulation and ordinary conduction cannot be properly separated 
when we are examining into their nature: that is, into the general law or laws 
under which their phenomena are produced. They appear to me to consist in 
an action of contiguous particles, dependent on the forces developed in electrical 
excitement; these forces bring the particles into a state of tension or polarity, 
which constitutes both induction and insulation ; and being in this state the 
contiguous particles have a power or capability of communicating these forces, 
one to the other, by which they are lowered and discharge occurs. Every body 
appears to discharge (444.987); but the possession of this capability in a greater 
or smaller degree in different bodies, makes them better or worse conductors, 
worse or better insulators: and both induction and conduction appear to be the 
same in their principle and action (1320), except that in the latter, an effect 
common to both is raised to the highest degree, whereas in the former, it occurs 
in the best cases, in only an almost insensible quantity. 
