The First Scientific American
Page 37
Franklin routs the mesmerists. “Le magnétisme dévoilé.” BIBLIOTHÈQUE NATIONALE DE FRANCE.
Finally, consider the aerial travel. The delightful globe Franklin saw from his terrace was spawned by the late war as well as the ongoing chemical experiments. In 1777, Joseph Montgolfier, from a family of paper manufacturers, had quizzed a doctor cousin about the new chemistry. From him, Montgolfier learned of the varying weights and qualities of different gases. Then, in 1782, Montgolfier pondered the long, unsuccessful, and bloody Spanish siege of the British at Gibraltar. Could the fortifications not be taken by air? he wondered. A device to carry bombs would be a remarkable, albeit dangerous, invention. Since ancient times, people had attempted aerial travel, which usually ended quite badly.11
Chemicals were the answer. In 1782 and 1783, Joseph Montolfier and his brother Étienne made containers (usually of cloth reinforced, appropriately, with paper) and filled them with air heated by a fire. They first tried box-shaped kites, but when they attempted to make them bigger, these rectangles proved perilously rigid. Bouncy bubbles, they discovered, would distribute the interior tension more evenly—and this has remained the classic shape for hot-air balloons. In June 1783, the Montgolfiers unveiled their invention—the Montgolfière— before an audience, sending a globe up about 3,000 feet to “general astonishment.”12
Imitators were quick to follow, and soon, many balloons soared over France. Some were filled with hydrogen made from iron filings and “vitriol” (sulfuric acid). These so-called Charlières were the creations of J.-A.-C. Charles and Barthélemy Faujas de Saint-Fond. (Earlier, Faujas had raised a subscription for Charles’s popular demonstrations of physics.) Hydrogen had greater lifting power, lasted longer, and interested chemical experimenters—all of which represented a big threat to the Montgolfiers. The Montgolfiers responded by launching the first manned flight (in November 1783), the one Franklin saw.13
Suddenly, balloons were the rage of Paris. They inspired everything, including (this being France, after all) fashionable clothing, interior decoration, and tableware. Soon, it was no longer sufficient to send a balloon aloft—it had to be gorgeously decorated and released to prove some new point. The subsequent contest between heated-air Montgolfières and inflammable-air Charlières brought about the first instance of inner-ear pain due to abrupt change in pressure (in December 1783), the first hijacking (in January 1784), the first air crash (in January 1785), and the first commercial flight (in January 1786). Each of the Montgolfier brothers received the title savant, or learned one, from the Académie Royale, though Charles received more attention from men of science. He shared the glory. At his own December 1783 liftoff, Charles respectfully asked Étienne Montgolfier to release a little pilot balloon to test the wind—and he gallantly toasted the crowd with champagne.14
Franklin, a former kite enthusiast, avidly watched these ventures into the sky, knew most of the balloonists, and was a touchstone for them. During the war, he had corresponded with the Montgolfier family patriarch about stationery and about getting letters to a Montgolfier relative in Canada. When Joseph and Étienne had requested an official Académie demonstration of their balloon, they remarked that it enabled the observation of electricity in clouds, science’s Franco-Franklinian topic. One Masonic admirer compared Joseph Montgolfier to Franklin. And before Charles turned to ballooning, Franklin had been one of his patrons. He had encouraged Charles’s chemical demonstrations, some of which used a glass armonica. (Seeing Franklin at a Charles lecture, an observer commented that it was like spotting Jupiter amid the mortals.) And it was as a designated witness of the Académie Royale that Franklin saw the ascent of the first successful aeronauts. 15
He marveled at aerostatics. He declared that “a few months since[,] the idea of witches riding thro’ the air upon a broomstick, and that of philosophers upon a bag of smoke, would have appeared equally impossible and ridiculous.” Le Roy sent him descriptions of the Montgolfiers’ work; he and Franklin, among others, wrote an official report on the Montgolfière as a technical device.16
Franklin immediately grasped that balloons were not only tremendous fun but also boons for philosophy. Their construction and motion confirmed the significance of temperature to fluid dynamics. As the first manned flight “went over our Heads,” he reported, “we could see the Fire [it carried,] which was very considerable. As the Flame slackens, the rarified Air cools and condenses, the Bulk of the Balloon diminishes and it begins to descend.” Of Charles’s little pilot balloon, Franklin concluded that its “falling at Vincennes shows that mounting higher it met with a current of air in a contrary direction, an observation that may be of use to future aerial voyagers.” Franklin appreciated that balloons were even airborne laboratories, with gondolas outfitted for philosophical aeronauts: “There is room in this car for a little table to be placed between them, on which they can write and keep their journal; that is, take notes of everything they observe, the state of their thermometer, barometer, hygrometer, etc.” One aeronaut even took samples of upper air for chemical analysis. (It was similar to air at sea level.)17
It was clear that ballooning was a young person’s activity—as when Cook had headed to the Pacific, Franklin could not hope to embark. But he enjoyed playing with miniature balloons, the fad in France in 1783. In September, he wrote Richard Price that “they make small Balloons now of the same material with what is called Gold-beater’s Leaf. Inclos’d I send one, which being fill’d with inflammable Air by my Grandson [Temple], went up last Night, to the Cieling in my Chamber, and remained rolling about there for some time. Please give it also to Sir Joseph Banks.” Yet again, an interior room or atmosphere gave Franklin all the experimental space he needed.18
Happily, balloons were invented too late to be used in the recent War of Independence. Instead, they symbolized the nascent peace. Frenchman Jean-Pierre François Blanchard and loyalist American John Jeffries made this point when they ballooned from England to France in 1785. Four years earlier, a big, unearthly globe approaching France would have seemed menacing, destined to be incinerated by Dr. Franklin’s rumored mirrors at Calais.
The craft barely made it across the channel, but that probably increased public interest in its intrepid mission. The balloon’s barometer is now considered the oldest surviving flight instrument; a portrait of Jeffries shows him, in a splendid fur cap, holding the barometer. And the Charlière bore mail. Jeffries called at Passy with the world’s first airmail letter, from loyalist William Franklin. Only in this way did William dare to contact his father and son. It was a “sweet reconciliation” indeed: an Anglo-Franco-American venture sailed over national boundaries and reconnected a family divided by war. Sadly, an excursion crossing from France to England in June 1785 ended horribly when its Montgolfière-Charlière hybrid exploded and its gondola plummeted to the rocks below. Its two aeronauts “were both found dashed to pieces,” as Franklin warned a would-be imitator.19
DESPITE the breathtaking tableaux all around him—science in midair!—Franklin found it hard to restart his own efforts. The casualty rate (Mesmer discredited, aeronauts dead) might have been a deterrent, but the real problem was the continued demand of public affairs. In October 1783, Franklin had discovered an incomplete letter on hygrometers to London instrument maker Edward Nairne, one that he had begun three years earlier. He finished and sent it, accepting Nairne’s forgiveness in advance: “You are so good as to consider how much my time has been taken up.” As during the war, he read and corresponded widely. He read the electrical work of others but did not attempt any himself; neither Volta’s electrophore nor Symmer’s socks tempted him back into experimentation. His rooms at Passy accumulated chemical books and equipment, but they were probably for his grandson, Temple.20
As he had done decades earlier, with Cadwallader Colden, Franklin used letters to ease himself into philosophy. From 1782 to 1785, he wrote several long letters on topics in science, addressing them to old friends such as Jan Ingenhousz or Benjamin Vau
ghan or to minor figures such as the Abbé Jean-Louis de Giraud-Soulavie, none of whom were likely to be overly critical. Franklin usually took up topics he already knew a great deal about, for instance, meteorology. If he discussed subjects that were new to him, he tended to focus on fields in which he would not be expected to do experiments, such as geomorphism.21
Franklin’s 1782 “Conjectures Concerning the Formation of the Earth” was characteristic. When he sent the essay to Soulavie, he confessed he had “given loose to imagination” because “actual observation” of nature was “out of my power.” In his essay, he reviewed the theories of others—Gottfried Wilhelm Leibnitz’s idea that the earth’s core might be fluid and Isaac Newton’s theory that gravity made matter converge on a common center. The “internal parts” of the resulting earth were, Franklin concluded, a “fluid more dense, and of greater specific gravity than any of the solids we are acquainted with; which therefore might swim in or upon that fluid.” The “surface of the globe” was a mere “shell, capable of being broken and disordered” by its fluid center, which probably held a great deal of iron. “The iron contained in the substance of this globe,” Franklin speculated, had “made it capable of becoming as it is a great magnet.” Further, “the fluid of magnetism exists perhaps in all space,” giving the “universe” a “magnetical North and North” and making interstellar travel possible.22
In his “Meteorological Imaginations and Conjectures” of 1784, Franklin was on even better form. In this letter, he addressed one of his oldest interests, the weather. Once again, he took up the idea that the atmosphere contained layers of warmth and cold. He hypothesized “a Region high in the Air over all Countries, where it is always Winter.” He believed that cold zone formed hail and snow and counterbalanced warmth from the sun and the heat-absorbing earth. (The fact that balloonists got colder as they ascended might have made him remember his earlier speculation.)23
Then Franklin noted, almost in passing, the “constant Fog over all Europe” in the summer of 1783. This oddly “dry” fog had occluded the sun and made the summer milder, and it brought winter on earlier than usual. Everyone noticed it, and everyone was mystified by it—except Franklin. A dry fog must be a form of smoke, he reasoned, but why was there so much smoke in the atmosphere? Maybe the earth had encountered one of “those great burning Balls or Globes,” he posited. In other words, a big comet might have entered and been destroyed by “our Atmosphere,” which then retained the smoke from the explosion. Or the fog might have come from a volcano. Mount Hecla in Iceland had recently erupted, as well as another “Volcano which arose out of the Sea near that Island, which Smoke might be spread by various Winds, over the northern Part of the World.” Lacking time to do experiments, scrambling to keep up with new discoveries, and recycling old conjectures, Franklin had hit on an important, if rare, aspect of climate change.24
So far, so good—and it is interesting that Franklin was finding his feet not in the electrical material that had catapulted him to fame but in the natural history he had first examined in his twenties and thirties. Luckily for him, he had salted away some data—his measurements of sea-surface temperature from his 1775 and 1776 crossings of the Atlantic. Unluckily, many other people shared his interest in the sea, which meant that Franklin would have to hurry to make anything of his findings.
His fame made it likely that colleagues and even competitors would seek his attention. A train of British guests at Passy (Polly Hewson came with her sons) included Thomas Pownall, an old friend and servant of empire. Pownall had been writing a piece entitled “Hydraulic and Nautical Observations on the Currents in the Atlantic Ocean,” and he sought Franklin’s opinion of it. On October 7, 1784, Franklin read the essay, a narrative description of the Gulf Stream and of investigations of it, including Franklin’s and those of others as well. He marked comments in the margins. Franklin did not correct and so presumably agreed with Pownall’s statements that he had, with Folger, produced a chart “at London in 1768,” had since had it “copied & Printed at Paris by Mr de Chaumont,” but had found it “not perfectly exact.” Franklin then gave Pownall “some notes” of his own on the subject. In these, he confirmed that he had made “several experiments with the Thermometer” to locate the Gulf Stream.25
From this visit, Pownall got Franklin’s imprimatur on his essay, and Franklin got credit in it for his own chart and for the first thermometric investigation of the Gulf Stream. But Franklin, ever attentive to the state of his scientific reputation, must have gotten the message that it was high time for him to publish his own study of the Gulf Stream. Neither of his two charts enjoyed wide circulation, and both bore another man’s description of the current—Timothy Folger’s sailing instructions were their only narrative material. Fortunately, developments in hydrography were not nearly as daunting as those in chemical or physical experiments. And of course, Franklin had been following innovations in maritime cartography and technology through the war. His patriotic diligence now came in handy.
Throughout the 1770s and 1780s, Franklin had steadily gathered information about affairs of the sea. Johann Reinhold Forster, one of the naturalists who had accompanied James Cook on his second Pacific journey, sent Franklin his Observations Made During a Voyage Round the World . . . (1778), with a final chapter containing “useful Directions for preserving the lives of mariners on long Voyages.” Le Roy and Franklin discussed Forster’s account. Le Roy noted that the lightning rod and chain on one ship had protected it during a storm at “Tahity.” Meanwhile, some of Franklin’s many “begging letters” had offered maritime inventions to the United States, in exchange for money or assistance in getting to America. Stephen Sayre sent several accounts of improved naval architecture, for example, and Franklin received promises to develop submarine vessels, none of which quite worked.26
Franklin’s patronage of the Continental Navy had, however, taught him which maritime innovations did work. The standout was copper sheathing. Placed over the hull of a ship, corrosion-resistant sheets of copper repelled the sea growths that sprouted on wooden vessels and made them slow and difficult to maneuver. The result was greater stability, or “stiffness.” It seems that the British Admiralty had begun sheathing its ships around 1778, and the Post Office soon followed suit. John Paul Jones had lobbied to command two captured, copper-bottomed ships. Pierre Landais, the Frenchman who commanded the Alliance, pleaded to have it sheathed: “She would still sail better, and be stiffer under sail at sea, which is what she wants to be.” Franklin had assented to Landais but regretted that funds did not allow for routine sheathing. “For God’s sake be sparing,” he had told Jones in 1780, “unless you mean to make me a Bankrupt.”27
Peace brought yet more maritime news. Of Franklin’s passport for Captain Cook, Sir Joseph Banks confessed, “I could not but rejoice at the triumph which such an indisputable proof afforded me over those who warp’d by politicks or party wish’d to entertain a different opinion of your character.” To thank Franklin, the Royal Society had, in 1780, nominated him for its gold medal bearing Cook’s image. Banks bestowed the medals on the monarchs of France, Britain, and Russia; Franklin did not get his until 1784, once peace was a firm fact. The same year, the Royal Society sent him a copy of Cook’s three-volume Voyages. Franklin was frustrated that the thank-you gift had been mispacked: the set lacked its first volume but had a duplicate of the third. That he cared about the missing volume showed that he remained interested in hydrography.28
He had no time just yet for even a speculative letter on maritime matters. Instead, he turned back to political arithmetic. His firm declarations on this long-gestating topic stood in marked contrasts to his diffident speculation on other areas of science—he knew exactly what he wanted to say about the population of a now independent United States.
He still assumed that America’s population was growing so fast that immigrants would not be needed. Yet no sooner did British troops stack their arms at Yorktown than petitions for assistance in emigrat
ing to America stacked up on his desk. Tired of answering each appeal, Franklin instead refashioned the bits of advice he had been dispensing since 1777 into “Information to Those Who Would Remove to America” (1782).29
Steadily and cheerfully, he gave would-be migrants the same advice : think twice. Franklin meant his essay to quash “mistaken Ideas and Expectations” about America. “[It] is the Land of Labour,” he cautioned, “and by no means what the English call Lubberland, and the French Pays de Cocagne,” where houses were “til’d with Pancakes, and where the Fowls fly about ready roasted, crying, Come eat me!” Though various colonies had formerly encouraged settlers “by Paying their Passages” or providing land, the current government did not. No one was worth the cost of importation. “Strangers” should go to the United States for its “good Laws and Liberty,” Franklin said, and because there was “room enough for them all.” He also warned any man who had “no other Quality to recommend him but his Birth” to stay put. Inherited rank was “a Commodity that cannot be carried to a worse market than that of America.” The United States had instead “a general happy Mediocrity.”30
Even men of learning and accomplishment were advised to think carefully before packing up. Few Americans were rich enough to “pay the high Prices given in Europe for Paintings, Statues, Architecture.” “The natural Geniuses, that have arisen in America with such [artistic] Talents,” he explained, “have uniformly quitted that Country for Europe.” Things were slightly better for those talented in “Letters and Mathematical Knowledge.” The nation’s “nine Colleges or Universities,” plus many small academies, promised a number of academic positions. The professions—divinity, law, and medicine—were also a good bet: “The quick Increase of Inhabitants everywhere gives them a Chance of Employ.” But European clerics, lawyers, and doctors would have to compete “with the Natives.”31