Naïve Insights and Ingenious Devices: Electricity

ON A RARE OCCASION, an American could discover something, even in physics, simply because he was less learned than his European colleagues. Ignorance of the respectable paths of scientific thought might leave him freer to wander off wherever facts beckoned. Such was no foundation for a solid tradition of speculative science, but it was not absolutely impossible to advance physics under American conditions. To exploit naïveté in a subject as cumulative as physics required great genius, but at least one colonial American—Benjamin Franklin—was able to do so.

Franklin’s concepts did of course grow in the context of Newtonian experimental science, but Franklin was not, and never pretended to be, well read in the Newtonian classics. The evidence even for his reading of Newton’s Optics is only circumstantial; everything confirms our suspicion that Franklin lacked the mathematical knowledge to understand Newton’s Principia or other works of similar difficulty. His theoretical equipment for advanced study in any of the physical sciences was meager.

Franklin’s actual accomplishment was obscured by extravagant comparison here and abroad to the greatest mathematical and physical theorists. John Adams declared his reputation “more universal than that of Leibnitz or Newton, Frederick or Voltaire.” Lord Chatham praised him in the House of Lords as “one whom all Europe held in high Estimation for his Knowledge and Wisdom, and rank’d with our Boyles and Newtons.” The great chemist Joseph Priestley declared Franklin’s discovery in his kite experiment “the greatest, perhaps since the time of Sir Isaac Newton.” Franklin’s special genius has been buried under the even less discriminating praise heaped on him since his death.

In fact his achievement illustrated the triumph of naïveté over learning. A clue to Franklin’s peculiar success as a “physicist” is found in the explanation for Cadwallader Colden’s failure. Colden, the New York official whose work as a naturalist we have already noted, aimed at greatness in the European mold. In his Principles of Action in Matter (1751), he professed to carry on the work of Newton, even to outdo Newton by providing a general theory of the “cause” of gravitation. Colden did not possess the specialized learning, the architectonic mind, nor the community with other learned physicists without which great works in mathematical physics have seldom been produced. Yet he pretended “to have discovered the true cause of the motion of the planets and comets, and from thence to deduce the reason of all the phaenomena, with that exactness as to agree with the most accurate observations.” Happily, he explained, all this would be accomplished, “without any aid of the conic sections, or of any other knowledge, besides the common rules of arithmetic and trigonometry:” Franklin, in contrast to Colden, had no illusion that he was at home in Newton’s mathematical world; he merely set out to explain certain specific phenomena. Colden’s work would probably have been of higher quality had he lived in Europe near the ancient seats of learning, but under such circumstances Franklin’s work might not have been done at all.

Electricity was where Franklin earned his reputation as a physicist; only there did he make physical discoveries of lasting significance. Franklin’s electrical discoveries were not embodied in treatises nor were they the minor premises of a large theory about the nature, origin, or causes of electricity, much less of all matter. His writings on electricity were diffuse and miscellaneous. His book, which became famous under the title Experiments and Observations on Electricity, made at Philadelphia in America, was actually a collection of letters, so loosely organized that some readers have doubted whether the items were intended for publication. They were not published as a book in America until 1941.

“He has endeavoured,” said Sir Humphry Davy, “to remove all mystery and obscurity from the subject. He has written equally for the uninitiated and for the philosopher; and he has rendered his details amusing as well as perspicuous, elegant as well as simple.” Even today the reader is amazed to find that so fundamental a work is so commonplace and non-mathematical in its language. This work, the basis of Franklin’s scientific reputation, reads more like a book of kitchen-recipes or instructions for parlor-magic than like a treatise on physics. In explaining “the wonderful effect of pointed bodies, both in drawing off and throwing off the electrical fire,” in one of his most important letters, he writes:

Place an iron shot of three or four inches diameter on the mouth of a clean dry glass bottle. By a fine silken thread from the cieling, right over the mouth of the bottle, suspend a small cork-ball, about the bigness of a marble; the thread of such a length, as that the cork-ball may rest against the side of the shot. Electrify the shot and the ball will be repelled to the distance of four or five inches, more or less, according to the quantity of Electricity.— — —When in this state, if you present to the shot the point of a long, slender, sharp bodkin, at six or eight inches distance, the repellency is instantly destroyed, and the cork flies to the shot. A blunt body must be brought within an inch, and draw a spark to produce the same effect.

In Franklin’s day it was possible to carry on important electrical experiments with kitchen equipment because the subject was still in its infancy, and had not yet begun to become mathematical. Of all the sciences which saw great advances in the 17th and 18th centuries electricity had had the least history. There was a great deal less to know, or to be ignorant of, in electricity than in astronomy or mathematical physics in general Since it seemed to have no practical application at the time, there was full scope for the play of idle curiosity. Franklin’s interest in electricity was, if anything, less “practical” than that of some of his contemporaries, for he doubted that electricity would ever be the medical cure-all that some were then predicting it would be. His amateur and non-academic frame of mind was his greatest advantage; like many another discovering American, he saw more because he knew much less of what he was supposed to see.

When Franklin first became interested in electricity, just after 1746, he knew very little of what had been done in Europe. Returning to Philadelphia after a trip to Boston, where he had happened to witness “electrical entertainments,” Franklin was delighted to find that the Library Company had received some glass tubes from Peter Collinson. Three fellow-amateurs joined him in repeating the experiments he had seen. Most active was Ebenezer Kinnersley, an ordained Baptist minister who never had a pulpit—“an ingenious neighbor,” according to Franklin, “who, being out of business, I encouraged to undertake showing the experiments for money.” The other two were Philip Syng (1703-1789), a silversmith by trade, and Thomas Hopkinson (1709-1751), a lawyer and the father of the ingenious Francis Hopkinson. Both were to be among the founders of the American Philosophical Society. The precise role of each in the important early experiments is not easy to assign, partly because Franklin showed no excessive modesty in his accounts. But no one of the miscellaneous group was primarily a “natural philosopher”; none held a regular university degree nor could have been called learned by English standards.

The Philadelphia amateurs were quite out of touch with the work of European natural philosophers. They thought that Syng had accomplished something novel and important when he “invented” a simple electrical machine: a sphere of glass that turned on an iron axle producing friction which collected the electricity. This seemed a great improvement over the “fatiguing exercise” of rubbing a glass tube. But machines like Syng’s had long before been used in England and were already popular among electrical experimenters on the continent.

It seems that Franklin’s only knowledge of earlier European work on electricity was what he had gained from his London correspondent Peter Collinson. That was not a great deal. Franklin reported to Collinson that he and his three Philadelphia collaborators were observing “some particular phaenomena, that we look upon to be new.” But he had no way of knowing whether these were really discoveries or had already been noticed by European scientists. Franklin’s later letters to Collinson (which became the book on electricity) continued to have the tantalizing quality of a journal by an explorer who does not know whether anyone has seen his land before.

If Franklin had been better informed of what European scientists had accomplished, he might not have dared to make his boldly simple suggestion: that electricity was a single fluid, not varying with the material from which it was produced. This was Franklin’s fundamental electrical discovery. The two forms of electricity he then described simply as “plus” and “minus,” depending on what he conceived to be the direction of the flow.

Sophisticated European thinking on the subject had already “advanced” to Du Fay’s more elaborate doctrine:

There are two distinct Electricities, very different from one another; one of which I call vitreous Electricity and the other resinous Electricity. The first is that of Glass, Rock-Crystal, Precious Stones, Hair of Animals, Wool, and many other Bodies. The second is that of Amber, Copal, Gum-Lack, Silk, Thread, Paper, and a vast Number of other Substances.

Franklin seems to have known nothing of Du Fay’s distinction. He proceeded directly from his own observations to his epochal assumption that all electricity was a single fluid. Even if Franklin had known the misleading distinction which European scientists had made, he might have offered his own simple explanation. But it would have required boldness of imagination from a man whose forte was not boldness but common sense. It is more likely that he would not have dared even to voice his revolutionary observation.

Fortunately for our understanding of Franklin’s work, we know what happened to his thinking after he became better acquainted with the writings of his European contemporaries. From the standard European writings on electricity, many of which Peter Collinson sent to the Library Company of Philadelphia, Franklin learned the respectable ideas and the conventional vocabulary. His own insights lost their freshness. As early as 1748, he showed a tendency to learn from books rather than from observation; he began to see things as his European contemporaries saw them. A pamphlet published in London in 1751 with four of Franklin’s letters on electricity offered nearly all his basic contribution to the subject. The more perceptive European scientists themselves feared that if Franklin acquired their learning he would soon see no more than they did. Pieter van Musschenbroek, discoverer of the principle of the condenser and an inventor of the Leyden jar, warned the American scientist. On receiving Franklin’s request for books on electricity in 1759, he urged him to “go on making experiments entirely on your own initiative and thereby pursue a path entirely different from that of the Europeans, for then you shall certainly find many other things which have been hidden to natural philosophers throughout the space of centuries.” Unfortunately, by this time Franklin had already become “learned” in electricity and the damage was done.

Franklin’s writings on electricity, then, were not exceptions to the descriptive, limited character of colonial science. With his usual good luck, Franklin had happened on a subject where his lack of mathematics was no disadvantage, where his lack of learning was in fact an advantage, and where the play of his idle curiosity could bear fruit. Here was hardly enough to justify Jefferson’s boast that America was already producing great physicists to vie with those of the Old World. Least of all did it show that America was a fruitful soil for basic scientific discoveries of a theoretical character. If it suggested anything, it was the contrary. American barrenness of other discoveries in the physical sciences during the colonial period only emphasized the atypical and coincidental character of Franklin’s discovery in this field.

The achievement by Franklin which most fired the popular imagination and which has been hallowed in American folklore, was even further from the rarefied world of Newtonian physics: his proof of the identity of lightning and electricity, and his invention of the lightning-rod thus made possible. Franklin’s famous experiment of the electrical kite was not a basic theoretical discovery. It was a clever way of putting to practical use the “power of points” and the “single fluid” theory of electricity, both of which had already been developed in Franklin’s letters. It was a combination of applied science and mechanical ingenuity. The identity of lightning and electricity had already been suspected by Europeans, but they had found no way to prove it. Franklin’s contribution was a simple device that, as he said, “might have occurred to any electrician,” but which somehow had not occurred to European physicists preoccupied with their “electrical machines,” their laboratory experiments, and their theoretical arguments among themselves.

When Dr. John Lining of Charleston asked Franklin how he had come to think of the kite experiment to test the identity of lightning and electricity, Franklin replied by quoting from his scientific journal:

Nov. 9, 1749. Electrical fluid agrees with lightning in these particulars: 1. Giving light. 2. Colour of the light. 3. Crooked direction. 4. Swift motion. 5. Being conducted by metals. 6. Crack or noise in exploding. 7. Subsisting in water or ice. 8. Rending bodies it passes through. 9. Destroying animals. 10. Melting metals. 11. Firing inflammable substances. 12. Sulphureous smell.—The electric fluid is attracted by points.—We do not know whether this property is in lightning.—But since they agree in all the particulars wherein we can already compare them, is it not probable they agree likewise in this? Let the experiment be made.

Once Franklin had proposed the obvious and only conclusive test of the hypothesis, several Europeans made the trial. They may even have pursued Franklin’s suggestion before Franklin himself got around to it.

The Abbé Nollet, one of the most “advanced” and learned of the French physicists and a leading exponent of the two-fluid theory, rejected such a direct appeal to “mere” observation. Franklin recounted in his Autobiography that Nollet, already offended by Franklin’s omission of his name from the Experiments and Observations on Electricity, “could not at first believe that such a work came from America and said it must have been fabricated by his enemies at Paris, to decry his system. Afterwards, having been assur’d that there really existed such a person as Franklin at Philadelphia, which he had doubted, he wrote and published a volume of letters, chiefly address’d to me, defending his theory, and denying the verity of my experiments, and of the positions deduc’d from them.” Still Franklin would not be drawn into quibbling over questions that could be settled only by observation. “My writings contain’d a description of experiments which any one might repeat and verify, and if not to be verifi’d, could not be defended…. I concluded to let my papers shift for themselves, believing it was better to spend what time I could spare from public business in making new experiments, than in disputing about those already made.”

So eager was Franklin for the application of his ideas, that in the very letter in which he proposed his experiment to test the identity of lightning and electricity (and even before the experiment had been made or his hypothesis had been confirmed), Franklin described the lightning-rod. “If these things are so,” he wrote from Philadelphia in 1749, “may not the knowledge of this power of points be of use to mankind, in preserving houses, churches, ships, &c. from the stroke of lightning, by directing us to fix on the highest part of those edifices, upright rods of iron made sharp as a needle, and gilt to prevent rusting, and from the foot of those rods a wire down the outside of the building into the ground, or down round one of the shrouds of a ship, and down her side till it reaches the water?” In Poor Richard’s Almanack for 1753, he published a simple description of a lightning-rod under the heading “How to secure Houses, &c. from Lightning.”

The lightning-rod quickly took hold in America. Even though academic learning on electricity was scarce, what men did know about electricity was soon put to more widespread practical use than in the great centers of European learning. We do not have reliable statistics, but observers from both sides of the Atlantic noticed that lightning-rods were more widely used in America than in England. “No country has more certainly proved the efficacy of electrical rods, than this,” the Rev. Andrew Burnaby noted as early as 1759 when he traveled through Virginia. Although buildings were sometimes struck by lightning, rods were so generally in use that it had become rare to hear of their being damaged. Burnaby hoped that this American example would inspire others to give up their religious prejudices against using scientific devices for human safety.

Even in America, however, the introduction of the lightning-rod had been delayed by religious prejudice and scientific conservatism. In 1755, soon after rods had first come into use, Boston was shaken by a severe earthquake, which the Rev. Thomas Prince explained in a new appendix to his sermon Earthquakes, The Works of God and Tokens of His Just Displeasure. “The more points of Iron are erected around the Earth, to draw the Electrical Substance out of the Air; the more the Earth must needs be charged with it…. In Boston are more erected than anywhere else in New England; and Boston seems to be more dreadfully shaken. O! there is no getting out of the mighty Hand of God! If we think to avoid it in the Air, we cannot in the Earth: Yes, it may grow more fatal.” But the sensible Professor John Winthrop, who understood Franklin’s points, read a lecture in the Harvard College Chapel to refute such wild imaginings; and the cases in which the rods had actually worked seemed in the popular mind to outweigh fancy theoretical objections. In London in 1772, Franklin found it curious that the English were only then beginning to use lightning-rods although in America rods had already been in common use for nearly 20 years and were found not only on public buildings, churches, and country mansions but even on small private houses.

The circumstances of life here had probably prodded the Americans. “Thunder Storms are much more frequent there [in America] than in Europe, …” Franklin wrote from London in 1772. “Here in England, the Practice [of using rods] has made a slower Progress, Damage by Lightning being less frequent, & People of course less apprehensive of Danger from it.” Meteorologists tell us that, although the frequency of thunderstorms in southern Canada is about the same as in Europe (occurring on the average on about eleven days in the year), the frequency increases as one goes south until thunderstorms are nearly seven times as frequent in states bordering the Gulf of Mexico (occurring on the average on about 72 days in the year). All such figures are crude, and it is possible that the weather was different in the 18th century. But we do have enough information to make us suspect that lightning and thunder were more frequent here than in Europe. At any rate they must have seemed more threatening to colonial Americans dispersed over a half-known continent.

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