The First Scientific American

by Joyce Chaplin

  Franklin explained the aurora borealis as the result of atmospheric density in northern regions, where cold kept electricity from entering the earth, as it could in warmer places. Imagine, he asked his readers, “a Room” heated “by a Stove.” Heated air rose to the ceiling, spreading down as it accumulated. This could be “render’d visible” in a real room by introducing smoke, which would “rise & circulate with the Air.” And “a Similar Operation is perform’d by Nature on the Air of this Globe.” The tropics were the stove within the globe’s “Atmosphere” and sent warm air rising, replaced by cooler air from the poles: “Thus a Circulation of Air is kept up in our Atmosphere as in the Room above mentioned.” To verify this motion, one could watch clouds move in “Currents of different & even opposite Direction,” according to thermal variation, or use a candle to see the different air currents in a heated room, with cool air (below) bending the flame in one direction and hot air (above) in the other.104

  Franklin’s illustration of the aurora borealis. Benjamin Franklin, Political, Miscellaneous and Philosophical Pieces (1779). HARVARD COLLEGE LIBRARY.

  This atmosphere created differences in the earth’s receptivity to electricity. The vapor arising in the tropics created motion in the air, which generated electricity; in warm climates, where the earth was “a good Conductor,” atmospheric electricity could easily discharge in the form of lightning. Frozen earth was less receptive; an electrified cloud was unable to discharge in cold climates, where it became “as a bottle [Leyden jar] overcharg’d.” Moreover, the cold air refracted the bursting electricity’s light. The electric rays would converge and diverge depending on whether a “Conducting Body” could receive them, so the light they emitted darted about in characteristically auroral patterns—thus, the light show on December 3.105

  Poor Richard would have admired Franklin’s thrifty use of old materials: his first experiment on heating systems is here, as well as chunks of his meteorologic work, all garnished with his fundamental discovery that lightning was a form of atmospheric electricity. In English and French, he had made clear that his “Suppositions and Conjectures” were just that. He made statements about thermal trends in the atmosphere but posed questions on the auroral lights themselves. It would be charitable to call the essay old-fashioned; Franklin’s image of a dangerously overcharged Leyden jar was outdated, meaning it ignored Volta’s electrophore, which placidly stored electricity for long periods. Yet he also bolstered his important claim that heat and electricity behaved similarly, each in relation to the physical “conductors” of its fluid motions.106

  Praise for the essay was rapturous, and Franklin received many solicitations for publication. The piece appeared in the June issue of the Journal de Physique, a new publication that reflected, in contrast to the Académie’s Mémoires, a more specialized focus on physical science. In a London version of 1779, the editor’s comment was three times as long as Franklin’s six-page thesis. All the praise—or flattery really—generally noted Franklin’s ability to comment on nature while attending to the fates of nations. The periodical Mémoires secrets marveled that the minister of a new republic found time to “amuse himself with physics.” This was the tenor of all American, French, and even British admiration.107

  Franklin was aware that experimental science remained beyond his reach—Ingenhousz’s reports of his painstaking experiments made that clear. Ingenhousz still divided his time between Vienna and London (he was now Lord Shelburne’s client, as Priestley had returned to his ministry) and was turning from electrical to chemical experiments, indeed following in Priestley’s path. Priestley’s trials of mice and mint had established that plants did something that sustained life in animals. He had hypothesized that plants somehow purified the tainted air that animals exhaled.

  Ingenhousz decided to investigate what plants did to air. He planned and executed an experiment that eventually required a prodigious 500 tests. In each, Ingenhousz put a plant, foliage end down, into a glass vessel, filled the vessel with water, and then inverted it into a larger container of water so the plant was upright yet still submerged. He then set everything in the sun and watched air bubbles gradually displace the water in the glass vessel. Plants kept in the dark did not do this, even if warmed as if by the sun. Assisted by light, plants produced air of their own accord; they did not even need gasping mice to exhale tainted air they would then purify. As Ingenhousz put it, common plants thus generated “common air,” the “invisible fluid which surrounds the whole earth.” “One of the great laboratories of nature for cleansing and purifying the air of our atmosphere,” Ingenhousz declared, “is placed in the substance of the leaves.”108

  Ingenhousz published his findings as Experiments upon Vegetables . . . (1779). He sent a copy to Franklin in late 1779, asking, in his lovely, approximate English, “whether I spended my time alltogeather useless.” Franklin hardly thought so. He extolled Igen-housz’s exhaling vegetables to a fellow of the American Philosophical Society as “the greatest discovery made in Europe for some time past.” Later scientists would claim that Ingenhousz had provided the first evidence of photosynthesis, a term Ingenhousz never used (and was no longer alive to assess). But at the time, Priestley disputed the findings—he found a direct chemical action, in which plants performed something on mephitic air, more convincing than Ingenhousz’s idea that light somehow stimulated plants to produce air. If this was possible, Priestley asked, should not Ingenhousz be able to define the physical process that achieved it? Franklin cautioned Ingenhousz not to weary the public and strain a friendship with a direct refutation of Priestley’s objections. He instead recommended his own strategy of allowing ideas to fend for themselves. 109

  That approach was ingenuous, if not ungrateful. It had been Ingenhousz, among others, who had, in fact, defended Franklin’s ideas against critics. And Ingenhousz lured Franklin back to experimentation. He hoped Franklin was “not lost to the world of Nature, tho many of your old friends thinck so”—it was very nearly a threat. The Dutchman proposed to Franklin to “steal from your political occupations consecrated only to the service of your own country, some hours for the benefit of whole mankind,” a cunning pitch.110

  At some point, Franklin had devised experiments to test the speed at which various metals conducted heat. He sent a written protocol and materials to Ingenhousz, who did the tests. These experiments built on Franklin’s earlier observations, as during Philadelphia’s hot summer of 1749, that different materials conducted heat (and electricity) differently. Ingenhousz dipped wires made of various metals into melted wax, cooled them, and then dipped their unwaxed ends in hot oil; the faster a wire shed its wax, the faster it must transfer heat down its length. He reported the results to Franklin, who assured his friend that the distant experiments gave him “a great deal of Pleasure.”111

  Perhaps Franklin and Ingenhousz busied themselves as much as they did with science in order to avoid corresponding about the war. Ingenhousz favored the Americans. He could state this in Vienna, murmur it at his patron’s house (Lord Shelburne had his own doubts about the war), but would have been unwise to proclaim it on the streets of London or write about it. In late 1780, he riskily wrote Franklin that he deplored Britain’s “cowardly, shameful, and unmanly” tactics and stressed “how necessary it is for the tranquillity of Europe that your Country should remain free.” It then dawned on Ingenhousz that Franklin might not be the only one to see the letter. He saw spies everywhere. (They were.) Early in 1781, he panicked when a letter from a mutual friend in Paris arrived only after it had been slit open. Ingenhousz resolved that his correspondence with Franklin should go via his French bankers, and he recommended against entrusting letters to servants, who might pocket the postage and discard the letters or pass them to the Paris police.112

  Was it so hard to keep philosophy and politics apart? Franklin had to make an effort. Once the United States retreated from privateering, he took the high ground, insisting that everyone respect the neutrality of let
ters and ships unrelated to the war. In December 1777, he issued a passport for Ingenhousz to travel between England and Austria; Ingenhousz was “not an Enemy of the said States, nor a Subject of Great Britain” but rather “a Person of distinguished Merit” traveling on “private” business. Franklin likewise forbade captains of American ships to “meddle with the Pacquets between Dover and Calais” while they still ran. And he commanded the captains not to attack ships engaged in peaceful pursuits. He first did so to protect supply ships bound for a Moravian mission on Labrador in 1778.113

  Franklin made an even grander gesture in March 1779, when he ordered protection for James Cook’s third Pacific voyage. The Duc de Croÿ had been pressing Franklin to issue such protection; finally, the American exclaimed, “with his sublime brevity, ‘It shall be done!’” Franklin issued letters to all U.S. and allied ships: let pass Cook’s vessels, devoted as they were to “the benefit of Mankind in general” and the exploration that “facilitates the Communication between distant Nations.” Franklin learned later that his passport postdated, by a month, Cook’s death in the Sandwich Islands—Pacific islanders proved deadlier than Atlantic privateers.114

  So science and politics could enjoy somewhat separate spheres. Franklin got letters to many of Britain’s men of science even after France closed its coast to British traffic in May 1779. The British stopped the Dover-Calais packet boat a month later, yet men of science still communicated, often via neutral Catholics. Spaniards delivered to Franklin publications from the Royal Society of Arts in 1778, before Spain entered the war. Two months after Priestley published his Experiments and Obser vations . . . (1778), he had a Catholic priest deliver a copy to Franklin. The same year, John Fothergill got a text on Linnaean botany to Franklin, and Franklin requested back issues of the Royal Society’s Philosophical Transactions, published since his departure from London in 1775. “I do not suppose that Politicks have so far taken the Lead of Philosophy” as to deny him the volumes, he declared. The society granted the request without discussion. Receiving later volumes, Franklin presented them to the Académie.115

  Indeed, Franklin’s philosophic reputation in Britain was flourishing. Ingenhousz easily published his defense of Franklinist electricity in the Philosophical Transactions in 1778, not otherwise a good year for Anglo-American relations. James Cook, in his A Voyage Towards the South Pole, and Round the World . . . (1777), praised Franklin as the author of “the most rational account I have read of water spouts.”116

  In London, Benjamin Vaughan produced a major edition of Franklin essays, Political, Miscellaneous, and Philosophical Pieces (1779). Franklin’s political position deterred neither the volume’s production nor its favorable review in the British press. Indeed, Vaughan did not even feel compelled to disguise his subject’s contributions to political affairs. He estimated that “no man ever made larger or bolder guesses than Dr. Franklin from like materials in politics and philosophy.” He opened the volume with “Observations on the Increase of Mankind,” Franklin’s first and most aggressive challenge to Britain. “Can Englishmen read these things,” Vaughan asked, “and not sigh at recollecting that the country which could produce their author, was once without controversy their own!” (Remember that Vaughan had, in 1777, sent Franklin those useful maps of the Great Lakes region.)117

  Even amid pronouncements about knowledge belonging to all humanity, Franklin employed science in an openly partisan manner. Once his nation was formally allied with France, he used his expertise to advise France’s military experts. One of Lavoisier’s official duties was to serve as keeper of the nation’s gunpowder. This task, as in England, involved both men of science and state officials. In 1779, a new powder magazine needed to be constructed. Franklin joined Lavoisier and Le Roy on an Académie committee to advise the project’s leaders. He and Lavoisier also tried to get chemical materials that were essential to the American war effort to the beleaguered states.118

  In addition, Franklin used the press to promote the American cause. He exulted to Richard Price that the printing press allowed modern people to “speak to nations; and good books and well written pamphlets have great and general influence.” But the press could also produce propaganda. As early as 1777, Franklin considered setting up a press at Passy for official U.S. purposes, and he began to buy French type. He later acquired a full press and even a British copying machine, which he described to customs officials, falsely, as a scientific instrument. (It was illegal to import printing machinery.) While Franklin used the press for personal writings, notably his bagatelles, he also turned out U.S. documents, including passports. His first product was an invitation to a triumphant Fourth of July party at Passy in 1779.119

  Franklin’s patriotism only partly masked a growing disillusionment with the war. When Priestley joked that his chemical experiments might discover “the Philosopher’s Stone” that would transform base materials into gold, Franklin made “a Request, that when you have found it you will take care to lose it again.” If not, he said, people would “continue slaughtring one another as long as they can find Money to pay the Butchers.” Five wearying years later, he told Joseph Priestley that he longed for “Leisure to search with you into the Works of Nature; I mean the inanimate, not the animate or moral part of them, the more I discover’d of the former, the more I admir’d them; the more I know of the latter, the more I am disgusted with them.” Franklin then teased the Reverend Priestley for his interest in saving human souls: “Perhaps as you grow older, you may look upon this as a hopeless Project, or an idle Amusement, repent of having murdered in mephitic air so many honest, harmless mice, and wish that to prevent mischief, you had used Boys and Girls instead.”120

  Franklin hoped that peace would return him and his friends to the convivial learning he had enjoyed in London. In a letter to Joseph Banks, he expressed his longing “for a Return to those peaceful Times, when I could sit down in sweet Society with my English philosophic Friends, communicating to each other new Discoveries, and proposing Improvements of old ones; all tending to extend the Power of Man over Matter.” By 1782, that prospect seemed to him infinitely sweeter than his life as one of “the Grandees of the Earth projecting Plans of Mischief.”121

  AND THEN, peace came. On November 11, 1781, Vergennes sent Franklin the news of the American victory at Yorktown, Virginia. The message arrived at eleven o’clock at night; it would have been welcome at three in the morning. The Franco-American defeat of the British vindicated the alliance and guaranteed a truce. It also demanded one final test of Dr. Franklin as a grandee not of the earth but of the ocean.

  To Franklin’s joy, the truce opened prison doors and made free communication between Americans and Britons possible again. In 1782, Parliament conceded that captive Americans had the formal status of prisoners of war. Franklin was pleased that British newspapers and parliamentary speeches used the word reconciliation—“it certainly means more than a mere peace. It is a sweet expression.” He hoped the war would end with a show of humane principles. When American prisoners were exchanged for imprisoned Britons, he ventured, “it would be well, if some Kindness were mix’d in the transaction, with regard to their comfortable accommodation on shipboard.” Franklin rejoiced when, in May 1782, David Hartley related the “general and absolute” British order to release all American prisoners. For his part, Hartley praised Franklin’s wish for “sweet rec-oncilation” between their countries.122

  But actual reconciliation proved difficult. It would require intricate procedures and arrays of carefully recruited diplomats. John Adams had his moment of glory—Congress appointed him minister plenipotentiary to negotiate with Britain and charged four other men, including Franklin, to help him.123

  Franklin was mostly sidelined. Attacks of gout and a kidney stone often left him prostrate. But even in absentia, he overshadowed his colleagues. The British peacemakers included Lord Shelburne, Ingenhousz’s patron, and Benjamin Vaughan, who had published Franklin’s Political, Miscellaneous, and Philo
sophical Pieces. Shelburne reopened correspondence with Franklin in April 1782, recalling their work on American affairs fifteen years earlier. He complimented Franklin on the “Compass of your Mind and of your Foresight” and offered greetings to “Madame Helvetius and the Abbé Morellet” before he remembered himself and deleted reference to these French advocates of American independence.124

  Polite greetings notwithstanding, it was the Seven Years’ War all over again. The interested parties disputed some of that war’s contested pieces of land and water in America, Africa, India, and Europe. As ever, Franklin worried about room for his nation’s teeming people but also about their access to the Mississippi River and to the Atlantic. Fishing and whaling raised particular problems that defied national boundaries. Britain regarded the fishing banks off Canada as essential places where they could get not only fish but also men bred to the sea—potential seamen. The French king and ministers wanted to expand French whaling, perhaps in cooperation with the dubiously American Nantucketers. And extraordinarily, Congress passed a resolution in early 1783 permitting British ships to protect Nantucket.125

  These unstable bargains could accumulate indefinitely, especially if the peace negotiations made several treaties rather than one. That was Franklin’s worst fear and one of long standing. As early as 1778, rumors had flown that Britain might offer independence to the United States if it signed a separate peace. Franklin protested that the Franco-American treaty made such a bargain impossible: “An obligation of Gratitude and Justice” bound the United States to “a Nation which is engaged in a War on her Account.” Without one binding document, he warned, Britain might continue a vindictive war against France, the most faithful ally of the new United States. Any “honest American would cut off his right hand rather than Sign an Agreement with England contrary to the spirit of it.” Yet even in 1781 and 1782, when honest Americans held the upper hand, Great Britain threatened to recognize U.S. independence only if it could continue war against the Republic’s allies, particularly the French and Spanish.126