Preface

LETTER I.

FROM

Mr Benj. Franklin, in Philadelphia.

TO

Mr Peter Collinson, F.R.S. London.

July 28, 1747.

SIR,

Here are my observations on M. Muschenbroek’s wonderful bottle.

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 its 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 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.

At every stroke of the tube, suppose a quantity equal to 1 is thrown in.

Then, after the first stroke, the quantity contain’d 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 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 spued back thro’ the wire, or flies out in loud cracks thro’ 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 {3}bottle, between the top and bottom, by some non-electric, touching 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 electrised, 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 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 electrised 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.

These 2 states of Electricity are the plus and minus. They are combined and balanced in this miraculous bottle!

5. The shock to the nerves (or convulsion rather) is from 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 shortest course, as Mr Watson justly observes.

But a communication with the floor is necessary for a person to be shocked.

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.