_ 130

[A] It can hardly be necessary for me to say here, that whatever
general state the carrier ball acquired in any place where it was
uninsulated and then insulated, it retained on removal from that
place, notwithstanding that it might pass through other places that
would have given to it, if uninsulated, a different condition.

1219. To comprehend the full force of these results, it must first be
understood, that all the charges of the ball B and the carrier are charges
by induction, from the action of the excited surface of the shell-lac
cylinder; for whatever electricity the ball B received by _communication_
from the shell-lac, either in the first instance or afterwards, was removed
by the uninsulating contacts, only that due to induction remaining; and
this is shown by the charges taken from the ball in this its uninsulated
state being always positive, or of the contrary character to the
electricity of the shell-lac. In the next place, the charges at _a_, _c_,
and _d_ were of such a nature as might be expected from an inductive action
in straight lines, but that obtained at _b_ is _not so_: it is clearly a
charge by induction, but _induction_ in _a curved line_; for the carrier
ball whilst applied to _b_, and after its removal to a distance of six
inches or more from B, could not, in consequence of the size of B, be
connected by a straight line with any part of the excited and inducing
shell-lac.

1220. To suppose that the upper part of the _uninsulated_ ball B, should in
some way be retained in an electrified state by that portion of the surface
of the ball which is in sight of the shell-lac, would be in opposition to
what we know already of the subject. Electricity is retained upon the
surface of conductors only by induction (1178.); and though some persons
may not be prepared as yet to admit this with respect to insulated
conductors, all will as regards uninsulated conductors like the ball B; and
to decide the matter we have only to place the carrier ball at _e_ (fig.
107.), so that it shall not come in contact with B, uninsulate it by a
metallic rod descending perpendicularly, insulate it, remove it, and
examine its state; it will be found charged with the same kind of
electricity as, and even to a _higher degree_ (1224.) than, if it had been
in contact with the summit of B.

1221. To suppose, again, that induction acts in some way _through or
across_ the metal of the ball, is neg