Philada. July 28. 1747
The inclosed is a Copy of my last, which went
by the Governour’s Vessel: since which we have received, by Mesnard
and Ouchterlony, Hill’s Theophrastus, Pemberton’s Dispensatory,
Wilson’s Electricity and some other Pamphlets. The Proprietor’s
handsome Present of a complete Electrical Apparatus &c. is also
come to Hand in good Order, and is put up in the Library; but
little has been done with it yet, the Weather having been
excessively hot and moist ever since it arrived. The Directors have
ordered his very kind Letter to be answered with the Thanks of the
Company. I suppose it will be done by this Ship, if her unexpected
sudden Departure does not prevent.
The necessary Trouble of copying long Letters
which perhaps, when they come to your Hands, may contain Nothing
new or worth your Reading, so quick is the Progress made with you
in Electricity, half discourages me from writing anymore on that
Subject. Yet I can not forbear adding a few Observations on Mr.
Muschenbroek’s wonderful Bottle. vizt.
1 The Non-electric, contained in the Bottle,
differs, when electrised from a Non-electric electrised out of the
Bottle in this; That the Electrical Fire of the latter is
accumulated on it’s Surface, and forms an Electrical
Atmosphere round it, of considerable Extent; but the Electrical
Fire is crouded into the Substance of the former; the Glass
confining it.
2 At the same Time that the Wire and Top of the
Bottle &c. is electrised positively or plus, the
Bottom of the Bottle is electrised negatively or
minus in exact Proportion. i.e. Whatever Quantity of
Electrical Fire is thrown in at [the] Top, an equal Quantity goes
out of the Bottom. To understand this, Suppose the common Quantity
of Electricity in each Part of the Bottle, before the Operation
begins, is equal to 20, and at every Stroke of the Tube, suppose a
Quantity equal to 1 is thrown in; then after the first Stroke, the
Quantity contained in the Wire and upper Part of the Bottle will be
21, in the Bottom. 19. After the second, the upper Part will have
22, the lower 18, and so on, till after 20 Strokes, the upper Part
will have a Quantity of Electrical Fire equal to 40, the lower
none: and then the Operation ends; for no more can be thrown into
the upper Part, when no more can be driven out of the lower Part.
If you attempt to throw more in, it is spued back thro’ the Wire,
or flies out in loud Cracks thro’ the Sides of the
Bottle.
3 The Equilibrium can not be restored in the
Bottle by inward Communication, or Contact of the Parts; but
it must be done by a Communication form’d without the
Bottle, between the Top and Bottom, by some Non-electric touching
both at the same Time. In which Case, if the Contact be large
especially, it is restored with a Violence and Quickness
inexpressible; or touching each alternately, in which Case the
Equilibrium is restored by Degrees.
4 As no more Electrical Fire can be thrown into
the Top of the Bottle, when all is driven out of the Bottom. So in
a Bottle not yet electrised, none can be thrown into the Top, when
none can get out of the Bottom; which happens either when
the Bottom is too thick, or when the Bottle is placed on an
Electric-per-se. Again, when the Bottle is electrised, but little
of the Electrical Fire can be drawn out from the Top, by
touching the Wire, unless an equal Quantity can at the same Time
get in at the Bottom. Thus place an Electris’d Bottle on
clean Glass or dry Wax, and you will not, by touching the Wire, get
out the Fire from the Top. Place it on a Non-electric, and touch
the Wire, you will get it out in a short Time; but soonest, when
you form a direct Communication, as above.
So wonderfully are these two States of
Electricity, the plus and minus combined and
ballanced in this miraculous Bottle! situated and related to each
other in a Manner that I can by no Means comprehend! If it were
possible that a Bottle should in one Part contain a Quantity of Air
strongly comprest, and in another Part a perfect Vacuum; We know
the Equilibrium would be instantly restored within. But here
we have a Bottle, containing at the same Time a Plenum of
Electrical Fire and a Vacuum of the same fire; and yet the
Equilibrium can not be restored between them but by a Communication
without! Tho’ the Plenum presses violently to expand, and the
hungry Vacuum seems to attract as violently in Order to be
filled.
5 The Shock to the Nerves (or Convulsion
rather) is occasioned by the sudden Passing of the Fire thro’ the
Body in its Way from the Top to the Bottom of the Bottle. The Fire
takes the shortest Course, as Mr. Watson justly observes; but he
was mistaken in supposing, that for a person to be shock’d a
Communication with the Floor is necessary (see Sequel p. 67,
68, 69). He that holds the Bottle with one Hand, and touches the
Wire with the other, will be shockt as much, tho’ his Shoes be dry,
or even standing on Wax, as otherwise. And on the Touch of the Wire
(or of the Gun Barrel, which is the same Thing) the Fire does not
proceed from the touching Finger to the Wire, as he supposes, but
from the Wire to the Finger, and passes thro’ the Body to the other
Hand, and so into the Bottom of the Bottle. We are all obliged to
that Gentleman for Publishing his ingenious Observations. It is
likely he has seen these little Mistakes himself before this Time;
and therefore it is hardly necessary to shew him what I write: If
you should, I hope, he will excuse the Freedom I have taken; it
being only in a private Letter; There is also some apparent
Contradiction between his No. XLVII and LXII in the Sequel which I
need not further point out.
Exper. I. Place an electrised Vial on Wax. A
small Cork Ball suspended by a dry Silk Thread held in your Hand,
and brought near to the Wire, will first be attracted and then
repell’d. When in this State of Repellency, sink your Hand, that
the Ball may be brought towards the Bottom of the Bottle, it will
there be instantly and strongly attracted, ’till it has parted with
it’s Fire. If the Bottle had an Electrical Atmosphere as well as
the Wire, an Electrified Cork would be repell’d from one as well as
from the other.
Exper. II [fig. 1]. From a bent Wire [(a)]
sticking in the Table, let a small Linen Thread [(b)] hang down
within half an Inch of the Electrised Vial [(c)]. Touch the Wire of
the Vial repeatedly with your Finger; and at every touch you will
see the Thread instantly attracted by the Bottle. This is best done
with a Vinegar Cruet, or some such belly’d Bottle. As soon as you
draw any Fire out from the upper Part, by touching the Wire, the
lower Part of the Bottle draws an equal Quantity in
by the Thread.
Exper. III [fig. 2]. Fix a Wire in the Lead,
with which the Bottom of the Bottle is armed [(d)], so as that
bending upwards, it’s Ring End may be level with the Top, or Ring
End of the Wire in the Cork [(e)], and at 3 or 4 Inches Distance.
Then electrise the Bottle, and place it on Wax. If a Cork suspended
by a Silk Thread [(f)] hang between these two Wires, it will play
incessantly from one to the other, ’till the Bottle is no longer
electrised. That is, it fetches and carries Fire from the Top to
the Bottom of the Bottle till the Equilibrium is restored.
Exper. IV [fig. 3]. Place in electricised Vial
upon Wax. Take a Wire [(g)] bent in the Form of a C, the Ends at
such a Distance when bent, as that the upper may touch the Wire of
the Bottle, when the lower touches the bottom; stick the outer Part
to a Piece of Sealing Wax [(h)] which will serve as a Handle. Then
apply the lower End to the Bottom of the Bottle, and gradually
bring the upper End near the Wire in the Cork: the Consequence is;
Spark follows Spark till the Equilibrium is restored. Touch the Top
first, and on approaching the Bottom with the other End, you have a
constant Stream of Fire from the Wire entering the Bottle. Touch
Top and Bottom together, and the Equilibrium will soon be restored
but silently and imperceptibly, the Contact being
small; the crooked Wire forming the Communication.
Exper. V [fig. 4]. Let a Ring of thin Lead or
Paper surround the Bottle [(i)], even at some Distance from or
above the Bottom: From that Ring let a Wire proceed up till it
touch the Wire of the Cork [(k)]. A Bottle, so fixt, can not by any
Means be electrised; the Equilibrium is never destroyed. For while
the Communication between the upper and lower Parts of the Bottle
is continu’d by the outside Wire what is driven out at Bottom is
constantly supplied from the Top. Hence a Bottle can not be
electrised that is foul or moist on the Outside.
Exper. VI. Place a Man on a Cake of Wax and
present him the Wire of the Electrified Vial to touch, you standing
on the Floor, and holding it in your Hand. As often as he touches
[it] he will be electrified plus, and any one standing on
the Floor may draw a Spark from him. The Fire in this Experiment
passes out of the Wire into him; and at the same Time out of your
Hand into the Bottom of the Bottle.
Exper. VII. Give him the electrified Vial to
hold, and do you touch the Wire. As often as you touch it, he will
be electrified minus, and may draw a Spark from any one
standing on the Floor. The Fire now Passes from the Wire to you,
and from him into the Bottom of the Bottle.
Exper. VIII. Lay two Books on two Glasses back
towards back, 2 or 3 Inches distant, set the electrified Vial on
one, and then touch the Wire; that Book will be electrified
minus; the Electrical Fire being drawn out of it by the
Bottom of the Bottle. Take off the Bottle, and holding it in your
Hand, touch the other Book with the Wire; that Book will be
electrified plus; the Fire passing into it from the Wire,
and the Bottle at the same Time supplied from your Hand. A
suspended small Cork Ball will play between these Books, ’till the
Equilibrium is restored.
Exper. IX. When a Body is electrised
plus it will repel an electrified Feather or small Cork
Ball. When minus (or when in [the] common State) it will
attract them; but stronger when minus than when in the
Common State, the Difference being greater.
Exper. X. Tho’ as in Expert. VI. a Man standing
on Wax may be electrised a Number of Times by repeatedly touching
the Wire of an electrised Bottle held in the Hand of one standing
on the Floor, he receiving the Fire from the Wire each Time; yet
holding it in his own Hand, and touching the Wire, tho’ he draws a
Strong Spark, and is violently shockt, no Electricity remains in
him; the Fire only passing thro’ him from the upper to the lower
Part of the Bottle. Observe, before the Shock, to let some one on
the Floor touch him, to restore the Equilibrium in his Body; for in
taking hold of the Bottom of the Bottle, he sometimes becomes a
little electrised minus, which will continue after the
Shock, as would also any plus Electricity he might have
given him before the Shock. For, restoring an Equilibrium in the
Bottle, does not at all effect the Electricity in the Man thro’
whom the Fire passes: that Electricity is neither increased nor
diminished.
Exper. XI. The Passing of the Electrical Fire
from the upper to the lower Part of the Bottle to restore the
Equilibrium, is rendered strongly visible by the following pretty
Experiment. Take a Book, whose Cover is filletted with Gold; bend a
Wire of 8 or 10 Inches long in this Form, slip it on the End of the
Cover of the Book, over the Gold line, so as that the Shoulder of
it may press on one End of the Gold Line, the Ring up, but leaning
towards the other End of the Book. Lay the Book on [a] Glass or
Wax; and on the other End of the Gold Line set the Bottle
electrised. Then bend the springing Wire, by pressing it with a
Stick of Wax, ’till it’s Ring approaches the Ring of the Bottle
Wire: instantly there is a strong Spark and Stroke, and the whole
Line of Gold, which completes the Communication between the Top and
bottom of the Bottle, will appear a vivid Flame, like the sharpest
Lightning. The closer the Contact between the Shoulder of the Wire
and the Gold at one End of the Line, and between the bottom of the
Bottle and the Gold at the other End, the better the Experiment
succeeds. The Room should be darkned. If you would have the whole
Filleting round the Cover appear in Fire at once, let the Bottle
and Wire touch the Gold in the diagonally opposite Corners.
The rest of this Letter on private Affairs.
To Peter Collinson Esqr. F. R. S. London