Front Page Titles (by Subject) XLVII: TO PETER COLLINSON - The Works of Benjamin Franklin, Vol. II Letters and Misc. Writings 1735-1753
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XLVII: TO PETER COLLINSON - Benjamin Franklin, The Works of Benjamin Franklin, Vol. II Letters and Misc. Writings 1735-1753 
The Works of Benjamin Franklin, including the Private as well as the Official and Scientific Correspondence, together with the Unmutilated and Correct Version of the Autobiography, compiled and edited by John Bigelow (New York: G.P. Putnam’s Sons, 1904). The Federal Edition in 12 volumes. Vol. II (Letters and Misc. Writings 1735-1753).
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TO PETER COLLINSON
Philadelphia, 1 September, 1747.
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 of writing any more on that subject. Yet I cannot forbear adding a few observations on M. Muschenbroek’s wonderful bottle.
1. The non-electric contained in the bottle differs, when electrized, from a non-electric electrized out of the bottle, in this: that the electrical fire of the latter is accumulated on its surface, and forms an electrical atmosphere round it of considerable extent; but the electrical fire is crowded into the substance of the former, the glass confining it.1
2. At the same time that the wire and the top of the bottle, &c., is electrized positively or plus, the bottom of the bottle is electrized negatively or minus, in exact proportion; that is, whatever quantity of electrical fire is thrown in at the top, an equal quantity goes out of the bottom.2 To understand this, suppose the common quantity of electricity in each part of the bottle, before the operation begins, is equal to twenty; and at every stroke of the tube, suppose a quantity equal to one is thrown in; then, after the first stroke, the quantity contained in the wire and upper part of the bottle will be twenty-one, in the bottom nineteen; after the second, the upper part will have twenty-two, the lower eighteen; and so on, till after twenty strokes, the upper part will have a quantity of electrical fire equal to forty, the lower part 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 spewed back through the wire, or flies out in loud cracks through the sides of the bottle.
3. The equilibrium cannot be restored in the bottle by inward communication or contact of the parts; but it must be done by a communication formed without the bottle, between the top and bottom, by some non-electric, touching or approaching both at the same time; in which case 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 electrized, none can be thrown into the top when none can get out at 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 electrized, 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.1 Thus, place an electrized 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 balanced 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 compressed, 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 cannot be restored between them but by a communication without, though 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 through the body in its way from the top to the bottom of the bottle. The fire takes the shortest2 course, as Mr. Watson justly observes. But it does not appear from experiment that, in order for a person to be shocked, a communication with the floor is necessary; for he that holds the bottle with one hand and touches the wire with the other, will be shocked as much, though 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 is supposed, but from the wire to the finger, and passes through the body to the other hand, and so into the bottom of the bottle.
Experiments confirming the above
Place an electrized phial 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 repelled; when in this state of repellency, sink your hand that the ball may be brought towards the bottom of the bottle. It will be there instantly and strongly attracted till it has parted with its fire.
If the bottle had a positive electrical atmosphere, as well as the wire, an electrified cork would be repelled from one as well as from the other.
Plate III., 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 electrized phial (c). Touch the wire or the phial repeatedly with your finger, and at every touch you will see the thread instantly attracted by the bottle. (This is best done by a vinegar-cruet, or some such bellied 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.
Fig. 2.—Fix a wire in the lead, with which the bottom of the bottle is armed (d), so as that, bending upwards, its ring-end may be level with the top or ring-end of the wire in the cork (e), and at three or four inches distance. Then electrize 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 electrized; that is, it fetches and carries fire from the top to the bottom1 of the bottle till the equilibrium is restored.
Fig. 3.—Place an electrized phial on wax; take a wire (g) in 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 on a stick 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 the top and bottom together, and the equilibrium will instantly be restored, the crooked wire forming the communication.
Fig. 4.—Let a ring of thin lead or paper surround a 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 fixed cannot by any means be electrized; the equilibrium is never destroyed; for while the communication between the upper and lower parts of the bottle is continued by the outside wire, the fire only circulates; what is driven out at bottom is constantly supplied from the top.1 Hence a bottle cannot be electrized that is foul or moist on the outside, if such moisture continue up to the cork or wire.
Place a man on a cake of wax, and present him the wire of the electrified phial 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.
Give him the electrical phial 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.
Lay two books on two glasses, back towards back, two or three inches distant. Set the electrified phial 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 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.
When a body is electrized plus, it will repel a positively 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.
Though, as in Experiment VI, a man standing on wax may be electrized a number of times by repeatedly touching the wire of an electrized 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, though he draws a strong spark, and is violently shocked, no electricity remains in him, the fire only passing through 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 of his body; for in taking hold of the bottom of the bottle he sometimes becomes a little electrized minus, which will continue after the shock, as would also any plus electricity which he might have given him before the shock. For restoring the equilibrium in the bottle does not at all affect the electricity in the man through whom the fire passes; that electricity is neither increased nor diminished.
The passing of the electrical fire from the upper to the lower part1 of the bottle, to restore the equilibrium, is rendered strongly visible by the following pretty experiment. Take a book whose covering is filleted with gold; bend a wire of eight or ten inches long in the form of (m), Fig. 5, slip it on the end of the cover of the book, over the gold line, so as that the shoulder of it may press upon 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,2 and on the other end of the gold line set the bottle electrized; then bend the springing wire by pressing it with a stick of wax till its 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 darkened. 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.
I am, &c.,
[1 ]See this opinion rectified in § 16 and 17, p. 242. The fire in the bottle was found by subsequent experiments not to be contained in the non-electric, but in the glass. 1748.
[2 ]What is said here, and after, of the top and bottom of the bottle, is true of the inside and outside surfaces, and should have been so expressed.
[1 ]See the preceding note, relating to top and bottom.
[2 ]Other circumstances being equal.
[1 ]That is, from the inside to the outside.
[2 ]Placing the book on glass or wax is not necessary to produce the appearance; it is only to show that the visible electricity is not brought up from the common stock in the earth.