These appearances we attempt to account for thus: We suppose, as
aforesaid, that electrical fire is a common element, of which every
one of the three persons abovementioned has his equal share, before
any operation is begun with the tube. _A_, who stands on wax and
rubs the tube, collects the electrical fire from himself into the
glass; and his communication with the common stock being cut off
by the wax, his body is not again immediately supplied. _B_,(who
stands on wax likewise) passing his knuckle along near the tube,
receives the fire which was collected by the glass from _A_; and
his communication with the common stock being likewise cut off, he
retains the additional quantity received.--To _C_, standing on the
floor, both appear to be electrised: for he having only the middle
quantity of electrical fire, receives a spark upon approaching _B_,
who has an over quantity; but gives one to _A_, who has an under
quantity. If _A_ and _B_ approach to touch each other, the spark is
stronger, because the difference between them is greater: After such
touch there is no spark between either of them and _C_, because the
electrical fire in all is reduced to the original equality. If they
touch while electrising, the equality is never destroyed, the fire
only circulating. Hence have arisen some new terms among us; we say
_B_, (and bodies like circumstanced) is electrised _positively_; _A_,
_negatively_. Or rather, _B_ is electrised _plus_; _A_, _minus_. And
we daily in our experiments electrise bodies _plus_ or _minus_, as
we think proper.--To electrise _plus_ or _minus_, no more needs to
be known than this, that the parts of the tube or sphere that are
rubbed, do, in the instant of the friction, attract the electrical
fire, and therefore take it from the thing rubbing: the same parts
immediately, as the friction upon them ceases, are disposed to give
the fire they have received, to any body that has less. Thus you may
circulate it, as Mr. Watson has shewn; you may also accumulate or
subtract it, upon, or from any body, as you connect that body with
the rubber or with the receiver, the communication with the common
stock being cut off. We think that ingenious gentleman was deceived
when he imagined (in his _Sequel_) that the electrical fire came down
the wire from the cieling to the gun-barrel, thence to the sphere,
and so electrised the machine and the man turning the wheel, &c. We
suppose it was _driven off_, and not brought on through that wire;
and that the machine and man, &c. were electrised _minus_; _i. e._
had less electrical fire in them than things in common.
As the vessel is just upon sailing, I cannot give you so large an
account of American electricity as I intended: I shall only mention
a few particulars more.--We find granulated lead better to fill the
phial with, than water, being easily warmed, and keeping warm and
dry in damp air.--We fire spirits with the wire of the phial.--We
light candles, just blown out, by drawing a spark among the smoke
between the wire and snuffers.--We represent lightning, by passing
the wire in the dark, over a china plate that has gilt flowers, or
applying it to gilt frames of looking-glasses, &c.--We electrise a
person twenty or more times running, with a touch of the finger on
the wire, thus: He stands on wax. Give him the electrised bottle in
his hand. Touch the wire with your finger, and then touch his hand
or face; there are sparks every time[22].--We encrease the force of
the electrical kiss vastly, thus: Let _A_ and _B_ stand on wax; or
_A_ on wax, and _B_ on the floor; give one of them the electrised
phial in hand; let the other take hold of the wire; there will be
a small spark; but when their lips approach, they will be struck
and shock'd. The same if another gentleman and lady, _C_ and _D_,
standing also on wax, and joining hands with _A_ and _B_, salute or
shake hands. We suspend by fine silk thread a counterfeit spider,
made of a small piece of burnt cork, with legs of linnen thread, and
a grain or two of lead stuck in him, to give him more weight. Upon
the table, over which he hangs, we stick a wire upright, as high as
the phial and wire, four or five inches from the spider: then we
animate him, by setting the electrified phial at the same distance
on the other side of him; he will immediately fly to the wire of
the phial, bend his legs in touching it, then spring off, and fly
to the wire in the table, thence again to the wire of the phial,
playing with his legs against both, in a very entertaining manner,
appearing perfectly alive to persons unacquainted. He will continue
this motion an hour or more in dry weather.--We electrify, upon wax
in the dark, a book that has a double line of gold round upon the
covers, and then apply a knuckle to the gilding; the fire appears
every where upon the gold like a flash of lightning: not upon the
leather, nor, if you touch the leather instead of the gold. We rub
our tubes with buckskin, and observe always to keep the same side to
the tube, and never to sully the tube by handling; thus they work
readily and easily, without the least fatigue, especially if kept in
tight pasteboard cases, lined with flannel, and sitting close to the
tube[23]. This I mention, because the European papers on electricity
frequently speak of rubbing the tube as a fatiguing exercise. Our
spheres are fixed on iron axes, which pass through them. At one end
of the axis there is a small handle, with which you turn the sphere
like a common grind-stone. This we find very commodious, as the
machine takes up but little room, is portable, and may be enclosed in
a tight box, when not in use. It is true, the sphere does not turn
so swift as when the great wheel is used: but swiftness we think
of little importance, since a few turns will charge the phial, &c.
sufficiently[24].