and in consequence a thin plate of air, or of
their own repulsive ethers exists between them.

Hence when two plates of zinc and silver are thus brought in to the
vicinity of each other, the plate of air between them, as they are not
in adhesive contact, becomes like a charged coated jar; and if these
two metallic plates are touched by your dry hands, they do not unite
their electricities, as the dry cuticle is not a sufficiently good
conductor; but if one of the metals be put above, and another under
the tongue, the saliva and moist mucous membrane, muscular fibres, and
nerves, supply so good a conductor, that this very minute electric
shock is produced, and a kind of pungent taste is perceived.

When a plate or pencil of silver is put between the upper lip and the
gum, and a plate or pencil of zinc under the tongue, a sensation of
light is perceived in the eyes, as often as the exterior extremities
of these metals are brought into contact; which is owing in like
manner to the discharge of a very minute electric shock, which would
not have been produced but by the intervention of such good conductors
as moist membranes, muscular fibres, and nerves.

In this situation, a sensation of light is produced in the eyes; which
seems to show, that these ethers pass through nerves more easily, than
through muscular flesh simply; since the passage of them through the
retina of the eyes from the upper gum to the parts beneath the tongue
is a more distant one, than would otherwise appear necessary. It is
not so easy to give the sensation of light in the eyes by passing a
small shock of artificially accumulated electricity through, the eyes
(though this may, I believe, be done) because this artificial
accumulated electricity, as it passes with greater velocity than the
spontaneous accumulations of it, will readily permeate the muscles or
other moist parts of animal bodies; whereas the spontaneous
accumulations of electricity seem to require the best of all
conductors, as animal nerves, to facilitate their passage.

4. In the Galvanic pile of Volta this electric shock becomes so much
increased, as to pass by less perfect conductors, and to give shocks
to the arms of the conducting person, if the cuticle of his hands be
moistened, and even to show sparks like the coated jar; which appears
to be effected in this manner. When a plate of silver is laid
horizontally on a plate of zinc, the plate of air between them becomes
charged li