Front Page Titles (by Subject) CXV: ELECTRICAL EXPERIMENTS - The Works of Benjamin Franklin, Vol. III Letters and Misc. Writings 1753-1763
Return to Title Page for The Works of Benjamin Franklin, Vol. III Letters and Misc. Writings 1753-1763
The Online Library of Liberty
A project of Liberty Fund, Inc.
Search this Title:
Also in the Library:
CXV: ELECTRICAL EXPERIMENTS - Benjamin Franklin, The Works of Benjamin Franklin, Vol. III Letters and Misc. Writings 1753-1763 
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. III (Letters and Misc. Writings 1753-1763).
About Liberty Fund:
Liberty Fund, Inc. is a private, educational foundation established to encourage the study of the ideal of a society of free and responsible individuals.
The text is in the public domain.
Fair use statement:
This material is put online to further the educational goals of Liberty Fund, Inc. Unless otherwise stated in the Copyright Information section above, this material may be used freely for educational and academic purposes. It may not be used in any way for profit.
Made in Pursuance of those made by Mr. Canton, dated December 6, 1753; with Explanations, by Benjamin Franklin
read at the royal society, december 18, 1755
Philadelphia, 14 March, 1755.
I. Electric atmospheres that flow round non-electric bodies, being brought near each other, do not readily mix and unite into one atmosphere, but remain separate and repel each other.
This is plainly seen in suspended cork balls and other bodies electrified.
II. An electric atmosphere not only repels another electric atmosphere, but will also repel the electric matter contained in the substance of a body approaching it, and, without joining or mixing with it, force it to other parts of the body that contained it.
This is shown by some of the following experiments.
III. Bodies electrified negatively, or deprived of their natural quantity of electricity, repel each other (or at least appear to do so by a mutual receding), as well as those electrified positively, or which have electric atmospheres.
This is shown by applying the negatively charged wire of a phial to two cork balls suspended by silk threads, and many other experiments.
Fix a tassel of fifteen or twenty threads, three inches long, at one end of a tin prime conductor (mine is about five feet long and four inches diameter) supported by silk lines.
Let the threads be a little damp, but not wet.
Pass an excited glass tube near the other end of the prime conductor, so as to give it some sparks, and the threads will diverge.
Because each thread, as well as the prime conductor, has acquired an electric atmosphere, which repels and is repelled by the atmospheres of the other threads; if those several atmospheres would readily mix, the threads might unite, and hang in the middle of one atmosphere, common to them all.
Rub the tube afresh, and approach the prime conductor therewith, crosswise, near that end, but not nigh enough to give sparks, and the threads will diverge a little more.
Because the atmosphere of the prime conductor is pressed by the atmosphere of the excited tube, and driven towards the end where the threads are, by which each thread acquires more atmosphere.
Withdraw the tube, and they will close as much.
They close as much, and no more, because the atmosphere of the glass tube, not having mixed with the atmosphere of the prime conductor, is withdrawn entire, having made no addition to or diminution from it.
Bring the excited tube under the tuft of threads, and they will close a little.
They close, because the atmosphere of the glass tube repels their atmospheres, and drives part of them back on the prime conductor.
Withdraw it, and they will diverge as much.
For the portion of atmosphere which they had lost returns to them again.
Excite the glass tube and approach the prime conductor with it, holding it across, near the end opposite to that on which the threads hang, at the distance of five or six inches. Keep it there a few seconds, and the threads of the tassels will diverge. Withdraw it, and they will close.
They diverge, because they have received electric atmospheres from the electric matter before contained in the substance of the prime conductor, but which is now repelled and driven away by the atmosphere of the glass tube from the parts of the prime conductor opposite and nearest to that atmosphere, and forced out upon the surface of the prime conductor at its other end, and upon the threads hanging thereto. Were it any part of the atmosphere of the glass tube that flowed over and along the prime conductor to the threads, and gave them atmospheres (as is the case when a spark is given to the prime conductor from the glass tube), such part of the tube’s atmosphere would have remained, and the threads continue to diverge; but they close on withdrawing the tube, because the tube takes with it all its own atmosphere, and the electric matter, which had been driven out of the substance of the prime conductor, and formed atmospheres round the threads, is thereby permitted to return to its place.
Take a spark from the prime conductor near the threads, when they are diverged as before, and they will close.
For by so doing you take away their atmospheres, composed of the electric matter driven out of the substance of the prime conductor, as aforesaid, by the repellency of the atmosphere of the glass tube. By taking this spark you rob the prime conductor of part of its natural quantity of the electric matter, which part so taken is not supplied by the glass tube, for, when that is afterwards withdrawn, it takes with it its whole atmosphere, and leaves the prime conductor electrized negatively, as appears by the next operation.
Then withdraw the tube, and they will open again.
For now the electric matter in the prime conductor returning to its equilibrium, or equal diffusion, in all parts of its substance, and the prime conductor having lost some of its natural quantity, the threads connected with it lose part of theirs, and so are electrized negatively, and therefore repel each other, by Principle III.
Approach the prime conductor with the tube, near the same place as at first, and they will close again.
Because the part of their natural quantity of electric fluid which they had lost is now restored to them again, by the repulsion of the glass tube forcing that fluid to them from other parts of the prime conductor; so they are now again in their natural state.
Withdraw it, and they will open again.
For what had been restored to them is now taken from them again, flowing back into the prime conductor, and leaving them once more electrized negatively.
Bring the excited tube under the threads, and they will diverge more.
Because more of their natural quantity is driven from them into the prime conductor, and thereby their negative electricity increased.
The prime conductor not being electrified, brings the excited tube under the tassel, and the threads will diverge.
Part of their natural quantity is thereby driven out of them into the prime conductor, and they become negatively electrized, and therefore repel each other.
Keeping the tube in the same place with one hand, attempt to touch the threads with the finger of the other hand, and they will recede from the finger.
Because the finger being plunged into the atmosphere of the glass tube, as well as the threads, part of its natural quantity is driven back through the hand and body by that atmosphere, and the finger becomes, as well as the threads, negatively electrized, and so repels, and is repelled by them. To confirm this, hold a slender, light lock of cotton, two or three inches long, near a prime conductor that is electrified by a glass globe or tube. You will see the cotton stretch itself out towards the prime conductor. Attempt to touch it with the finger of the other hand, and it will be repelled by the finger. Approach it with a positively charged wire of a bottle, and it will fly to the wire. Bring it near a negatively charged wire of a bottle, it will recede from that wire in the same manner that it did from the finger; which demonstrates the finger to be negatively electrized, as well as the lock of cotton so situated.
Turkey killed by Electricity.—Effect of a Shock on the Operator in making the Experiment
As Mr. Franklin, in a former letter to Mr. Collinson, mentioned his intending to try the power of a very strong electrical shock upon a turkey, that gentleman accordingly has been so very obliging as to send an account of it, which is to the following purpose:
He made first several experiments on fowls, and found that two large, thin glass jars gilt, holding each about six gallons, were sufficient, when fully charged, to kill common hens outright; but the turkeys, though thrown into violent convulsions, and then lying as dead for some minutes, would recover in less than a quarter of an hour. However, having added three other such to the former two, though not fully charged, he killed a turkey of about ten pounds weight, and believes that they would have killed a much larger. He conceited, as himself says, that the birds killed in this manner eat uncommonly tender.
In making these experiments, he found that a man could, without great detriment, bear a much greater shock than he had imagined; for he inadvertently received the stroke of two of these jars through his arms and body, when they were very near fully charged. It seemed to him a universal blow throughout the body from head to foot, and was followed by a violent, quick trembling in the trunk which went off gradually in a few seconds. It was some minutes before he could recollect his thoughts so as to know what was the matter; for he did not see the flash, though his eye was on the spot of the prime conductor, from whence it struck the back of his hand; nor did he hear the crack, though the by-standers said it was a loud one; nor did he particularly feel the stroke on his hand, though he afterwards found it had raised a swelling there of the bigness of half a pistol-bullet. His arms and the back of the neck felt somewhat numbed the remainder of the evening, and his breast was sore for a week after, as if it had been bruised. From this experiment may be seen the danger, even under the greatest caution, to the operator, when making these experiments with large jars; for it is not to be doubted but several of these fully charged would as certainly, by increasing them in proportion to the size, kill a man, as they before did a turkey.