Franklin was the first scientist to propose that the identity of lightning and electricity could be proved experimentally, but he was not the first to suggest that identity, nor even the first to perform the experiment.4 For many years pioneer electricians had noted the similarity between electrical discharges and lightning, and in 1746 John Freke in England and Johann Heinrich Winkler in Germany separately advanced the idea of identity and suggested theories to account for it. Franklin’s later adversary the Abbé Nollet wrote to the same effect in 1748.5 Franklin and his Philadelphia collaborators, working independently, also observed the similarities, and in his letter of April 29, 1749, to John Mitchell on thundergusts he took as the basis for his entire discussion the hypothesis that clouds are electrically charged.6 In the “minutes” he kept of his experiments he listed under the date of November 7, 1749, twelve particulars in which “electrical fluid agrees with lightning,” and noted further that “the electrical fluid is attracted by points,” but that it was not yet known whether this property was also in lightning. “But since they agree in all other particulars wherein we can already compare them, is it not probable they agree likewise in this? Let the experiment be made.”7

However obvious the suggestion of such an experiment may now seem, no one had made it before. Herein lies Franklin’s principal claim to priority in this great discovery. A test of lightning required the prior discoveries embodied in the “doctrine of points,” of which he was the undisputed author, and the knowledge he had gained of the role of grounding in electrical experiments. It was the pointed metal rod, with its peculiar effectiveness in electrical discharge, which both led to the suggestion and facilitated the experiment.

In the following March Franklin, writing to Collinson, suggested that pointed rods, instead of the usual round balls of wood or metal, be placed on the tops of weathervanes and masts, and that they would draw the electrical fire “out of a cloud silently,” thereby preserving buildings and ships from being struck by lightning.8 He repeated the suggestion in July 1750 in his “Opinions and Conjectures,” with the important addition that a wire be run down from the rod to the ground or water, and he then proposed the “sentry-box” experiment. This was the first public suggestion of an experiment to prove the identity of lightning and electricity.9

According to Joseph Priestley, who almost certainly received his information directly from Franklin about fifteen years later, he did not perform the experiment himself at once because he believed a tower or spire would be needed to reach high enough to attract the electrical charge from a thunder cloud, and there was no structure in Philadelphia he deemed adequate for the purpose. Presumably he was waiting until Christ Church steeple, then in the early discussion stage, should be erected.1 English scientists, who could have read Franklin’s proposal when it was published in Experiments and Observations in April 1751, apparently failed to recognize its significance. But about a year later, in the spring of 1752, when a translation had been published in Paris, the French reaction was very different. Delor, “master of experimental philosophy,” repeated most of Franklin’s experiments before the King, and then in May Dalibard, Franklin’s translator, and Delor each set up apparatus which performed successfully the “Philadelphia experiment” of drawing electricity from a thunder cloud.2 Word of these achievements awoke the English electricians, and during the summer of 1752 the experiment was repeated several times in England as well as in France and Germany.3

At some time during 1751 or 1752 Franklin got the idea that he could send his conductor high enough by means of a kite, and that if it were flown during a thunder shower, the wet string might serve to bring the electrical charge down within reach. When the idea first came to him and just when he carried it out cannot be established with absolute certainty. Priestley wrote that the famous experiment with kite and key took place during June 1752, and the present editors believe there is no good reason to doubt the correctness of this date. If so, then Franklin performed his experiment before he learned of what Dalibard and Delor had done in France.

Almost never during these years did Franklin report a particular electrical experiment until some time had elapsed and this affair seems to have been no exception. Word of Dalibard’s and Delor’s successes reached Philadelphia toward the end of August and the Pennsylvania Gazette of August 27 carried a short account reprinted from the May issue of the London Magazine. During September Franklin erected a lightning rod on his own house, ingeniously equipping it with bells that would ring when the wire became charged and thus notify him when the atmosphere above the house was electrified.4 Then at last, on October 19, he printed in the Gazette a brief statement about the kite experiment with instructions for repeating it. The text of this statement, transmitted to Collinson, was read to the Royal Society on December 21. Neither in this paper nor at any later time did Franklin—or Priestley on his behalf—ever claim priority in carrying out the experiment he had been the first to propose.5

The same October 19 issue of the Gazette also announced that Poor Richard for 1753 was then “In the Press, and speedily will be published”; in that almanac Franklin printed for the first time precise instructions for the erection of lightning rods for the protection of buildings.6 The sequence of events in this somewhat complicated chain may be clarified by the following chronology:

Unfortunately, Franklin’s statement of the kite experiment has not been found in his own handwriting. Two text versions survive: that printed in the Pennsylvania Gazette of October 19, 1752, reprinted below; and a copy in the hand of Peter Collinson, now in the Royal Society.7 Aside from unimportant variations in paragraphing, spelling, capitalization, and punctuation, the Collinson copy differs from the Gazette version in several respects: (1) It is headed “From Benn: Franklin Esqr To P Collinson” and is dated “Philadelphia Octo: 1: 1752.” (2) At the end, following the words “compleatly demonstrated,” Collinson skipped the equivalent of about three lines, then added in two lines: “See his Kite Experiment” and “to be printed with the rest.” These lines were later struck out. (3) In the intervening space and running on to the right of the two canceled lines appears the following insertion not in Collinson’s hand, but in one which is strikingly like that of William Watson: “I was pleased to hear of the Success of my experiments in France, and that they there begin to Erect points on their buildings. Wee had before placed them upon our Academy and Statehouse Spires.” (4) The paper is endorsed in the hand of a Royal Society clerk: “Letter of Benjamin Franklin Esq to Mr. Peter Collinson F.R.S. concerning an Electrical Kite. Read at R.S. 21 Decemb. 1752. Ph. Trans. XLVII. p. 565.”

These text differences present several puzzles. The heading and date (item 1) have led several writers8 to believe that the text which follows is an extract of a letter from Franklin to Collinson of October 1, written more than two weeks before the statement was printed in the Gazette. In that case the Gazette text would be an extract from this earlier letter to Collinson. This is possible, but it leaves unexplained Franklin’s undated letter to Collinson, assigned below (p. 376) to the latter part of October, in which he wrote that he was sending, among other items, “my kite experiment in the Pennsylvania Gazette.” If what he had printed in the Gazette was indeed a passage from a letter already sent to Collinson, there would seem to have been no need to send him another copy of it. Conceivably, Collinson’s pen slipped when he wrote “Octo: 1,” as it occasionally did in referring to other Franklin letters, and he should have written “19,” “21,” or “31,” in which case he might have been copying the Gazette statement enclosed in Franklin’s later letter. Subsequent correspondence between the two men does not clarify the point.

The canceled addendum at the bottom (item 2) seems to have been intended as an instruction to a printer. Possibly Collinson first meant this paper for the printer of the 1753 Supplement of Experiments and Observations, and then decided to submit this copy to the Royal Society instead. But the question remains unexplained why he should have written “See his Kite Experiment,” when this document itself is the kite experiment, and is the only account of it we have in Franklin’s own words. The endorsement (item 4) presents no problem. The fact that the paper is lodged in the Royal Society makes it clear that this endorsement was added later for filing purposes after it had been printed in the Philosophical Transactions.

This leaves for consideration item 3, the short paragraph added to Collinson’s paper which mentions the French experiments and the erection of “points” in France and Philadelphia. The facts that it is written in a different hand from Collinson’s and that it is clearly an addition have not been considered by previous commentators. The paragraph has been taken as evidence that lightning rods were erected on the Academy building and the State House (Independence Hall) before October 1, 1752. The words are doubtless Franklin’s, though they have not been traced with certainty to any surviving document of his. If they were in fact part of a letter of October 1 to Collinson which also contained the original text of the statement on the kite experiment, then they must have been added to Collinson’s copy by someone else, probably Watson, who saw the original letter and thought this passage more important than Collinson had done. Or the paragraph may have been part of the later undated letter, probably of late October (the full text of which may not have been printed in the 1753 Supplement), with which Franklin enclosed the item on the kite experiment from the Gazette. Whatever the source, the paragraph must have been written by about November 1, 1752, in order for it to be read to the Royal Society as part of the report on the kite experiment on December 21 and printed as such in the Philosophical Transactions.9 The probable date for the erection of the two Philadelphia lightning rods is not materially affected in any case. The problem of the source of this added paragraph is not resolved by any printed version of Franklin’s account. The Philosophical Transactions printed the text from Collinson’s copy. The Gentleman’s Magazine and London Magazine and the 1753 Supplement to Experiments and Observations also printed the report, but all three followed the dating and text of the Gazette version, not the Collinson copy.1

It will be noticed that Franklin’s paper is not really an account of the kite experiment, but rather a brief statement that the experiment had taken place, followed by instructions as to how it could be successfully repeated. Franklin never, so far as is known, wrote out a narrative of his experience. The most detailed account that has survived is that which Joseph Priestley inserted in 1767 in his History of Electricity. There is every reason to believe that he learned the details directly from Franklin, who was in London at the time Priestley wrote the book. Franklin encouraged him to undertake the work and Priestley acknowledged in his preface the information Watson, Franklin, and Canton had supplied him. The account of the kite experiment, as Priestley wrote it about fifteen years after the event, may err in some details through faulty memory on Franklin’s part or misunderstanding on the Englishman’s, but it is probably correct in all major respects. In any case, since it is the nearest thing we have to a contemporary, first-hand account of one of the most famous episodes in Franklin’s career, it is reprinted here directly following Franklin’s statement.