Benjamin Franklin Experiments With Electricity

Introducing Franklin and the Kite,
serialized in five easy 5 minute installments.

Benjamin Franklin made two important discoveries in electricity: (a) identifying lightning as electricity and (b) identifying two charges, positive and negative, to electricity.

The ancients had no scientific acquaintance with electricity. The early Greeks, so far as known, observed but a single phenomenon in connection with it — the electrification of amber by friction. Aristotle and Pliny note the production of electricity by certain fishes, especially the torpedo, a ray possessing an electrical apparatus with which it kills or stuns its prey and defends itself against its enemies. Not before the sixteenth century of the Christian era was there any recorded scientific study of electrical phenomena. The early predecessors of Franklin, such as Gilbert, Boyle, and others, are considered to have created the science of electricity and magnetism. The invention of the Leyden jar or vial, in 1745, said to have been “hit upon by at least three persons working independently,” was a very important advance.

The work of Franklin, following so soon upon the then latest step of progress in Europe, is best made known to the world through his own writings, particularly in the letters, selected by Bigelow, which appear in this selection from his book.

This selection from The Complete Works of Benjamin Franklin; Including His Private as Well as His Official and Scientific Correspondence, and Numerous Letters and Documents Now for the First Time Printed, With Many Others not Included in any Former Collection, Also, the Unmutilated and Correct Version of His Autobiography by John Bigelow (edited) and by Benjamin Franklin published in 1887. The selection is serialized in five installments for daily reading.

Time: 1747 – 1752
Place: Philadelphia

While on a visit to Boston in 1746 Franklin witnessed some electrical experiments performed by a Mr. Spence, recently arrived from Scotland. Shortly after his return to Philadelphia the Library Company received from Mr. Collinson, of London, and a member of the Royal Society, a glass tube, with instructions for making experiments with it. With this tube Franklin began a course of experiments which resulted in discoveries which, humanly speaking, seem to be exerting a larger material influence upon the industries of the world than any other discovery of the human intellect. Dr. Stuber, then a resident of Philadelphia, and author of the first continuation of Franklin’s Life, who seems to have enjoyed peculiar opportunities of obtaining full and authentic information upon the subject, gives us the following account of the observations which this letter brought for the first time to the notice of the world through Mr. Collinson.

“His observations,” says Dr. Stuber, “he communicated, in a series of letters, to his friend Collinson, the first of which is dated March 28, 1747. In these he shows the power of points in drawing and throwing off the electrical matter which had hitherto escaped the notice of electricians. He also made the grand discovery of a plus and minus, or of a positive and negative, state of electricity. We give him the honor of this without hesitation; although the English have claimed it for their countryman, Dr. Watson. Watson’s paper is dated January 21, 1748; Franklin’s, July 11, 1747, several months prior. Shortly after Franklin, from his principles of the plus and minus state, explained in a satisfactory manner the phenomena of the Leyden vial, first observed by Mr. Cuneus, or by Professor Muschenbroeck, of Leyden, which had much perplexed philosophers. He showed clearly that when charged the bottle contained no more electricity than before, but that as much was taken from one side as was thrown on the other; and that to discharge it nothing was necessary but to produce a communication between the two sides, by which the equilibrium might be restored, and that then no sign of electricity would remain. He afterward demonstrated by experiments that the electricity did not reside in the coating, as had been supposed, but in the pores of the glass itself. After a vial was charged he removed the coating, and found that upon applying a new coating the shock might still be received. In the year 1749 he first suggested his idea of explaining the phenomena of thunder-gusts and of the aurora borealis upon electrical principles. He points out many particulars in which lightning and electricity agree, and he adduces many facts, and reasonings from facts, in support of his positions.

“In the same year he received the astonishingly bold and grand idea of ascertaining the truth of his doctrine by actually drawing down the lightning, by means of sharp-pointed iron rods raised into the region of the clouds. Even in this uncertain state his passion to be useful to mankind displayed itself in a powerful manner. Admitting the identity of electricity and lightning, and knowing the power of points in repelling bodies charged with electricity, and in conducting their fires silently and imperceptibly, he suggested the idea of securing houses, ships, etc., from being damaged by lightning, by erecting pointed rods that should rise some feet above the most elevated part, and descend some feet into the ground or water. The effect of these he concluded would be either to prevent a stroke by repelling the cloud beyond the striking distance, or by drawing off the electrical fire which it contained; or, if they could not effect this, they would at least conduct the electric matter to the earth without any injury to the building.

“It was not till the summer of 1752 that he was enabled to complete his grand and unparalleled discovery by experiment. The plan which he had originally proposed was to erect, on some high tower or other elevated place, a sentry-box, from which should rise a pointed iron rod, insulated by being fixed in a cake of resin. Electrified clouds passing over this would, he conceived, impart to it a portion of their electricity, which would be rendered evident to the senses by sparks being emitted when a key, the knuckle, or other conductor was presented to it. Philadelphia at this time afforded no opportunity of trying an experiment of this kind. While Franklin was waiting for the erection of a spire, it occurred to him that he might have more ready access to the region of clouds by means of a common kite. He prepared one by fastening two cross sticks to a silken handkerchief, which would not suffer so much from the rain as paper. To the upright stick was affixed an iron point. The string was, as usual, of hemp, except the lower end, which was silk. Where the hempen string terminated, a key was fastened. With this apparatus, on the appearance of a thunder-gust approaching he went out into the commons, accompanied by his son, to whom alone he communicated his intentions, well knowing the ridicule which, too generally for the interest of science, awaits unsuccessful experiments in philosophy. He placed himself under a shed, to avoid the rain; his kite was raised, a thunder-cloud passed over it, no sign of electricity appeared. He almost despaired of success, when suddenly he observed the loose fibers of his string to move toward an erect position. He now presented his knuckle to the key and received a strong spark. How exquisite must his sensations have been at this moment! On this experiment depended the fate of his theory. If he succeeded, his name would rank high among those who had improved science; if he failed, he must inevitably be subjected to the derision of mankind, or, what is worse, their pity, as a well-meaning man, but a weak, silly projector. The anxiety with which he looked for the result of his experiment may be easily conceived. Doubts and despair had begun to prevail, when the fact was ascertained, in so clear a manner that even the most incredulous could no longer withhold their assent. Repeated sparks were drawn from the key, a vial was charged, a shock given, and all the experiments made which are usually performed with electricity.

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