The First American: The Life and Times of Benjamin Franklin (122 page)

“How so?” inquired Franklin.

“When my daughter appeared with it at meeting, it was so much admired that all the girls resolved to get such caps from Philadelphia; and my wife and I computed that the whole could not have cost less than a hundred pounds.”

The farmer broke in. “But you do not tell all the story. I think the cap was nevertheless an advantage to us, for it was the first thing that put our girls upon knitting worsted mittens for sale at Philadelphia, that they might have wherewithal to buy caps and ribbons. And you know that industry has continued, and is likely to continue and increase to a much greater value, and answer better purposes.”

To which Franklin added, in his letter to Vaughan, “Upon the whole, I was more reconciled to this little piece of luxury, since not only the girls were made happier by having fine caps, but the Philadelphians by the supply of warm mittens.”

Speculation
on economics complemented Franklin’s musings on other matters. For a decade his political and diplomatic labors had largely kept him from philosophy, but the conclusion of the peace talks allowed a return to his true intellectual passion. In 1784 he sent a paper to the Literary and Philosophical Society of Manchester, entitled “Meteorological Imaginations and Conjectures,” which showed that his ability to reason from everyday observation to important insight about the natural world had not diminished. “There seems to be a region high in the air over all countries, where it is always winter, where frost exists continually,” he
wrote. The evidence? Hail, which fell even during the warmest months and occasionally acquired impressive dimensions. “How immensely cold must be the original particle of hail which forms the future hailstone, since it is capable of communicating sufficient cold, if I may so speak, to freeze all the mass of vapour condensed round it, and form a lump of perhaps six or eight ounces in weight!”

The winter of 1783–84 had been the coldest in many years. Franklin linked it to a “dry fog” that had been observed throughout the Northern Hemisphere the previous summer—which, he conjectured, was no fog at all but smoke from the Hecla volcano in Iceland, spread by the prevailing winds. Whatever its source, this persistent pall had diminished the solar energy reaching the earth, to such a degree that when concentrated by a burning (or magnifying) glass, the sun’s rays that summer scarcely kindled brown paper. The surface of the earth consequently never acquired the heat that typically moderates winter weather, Franklin explained; hence the bitter season that followed.

This surprisingly modern account of the weather was followed by an even more ambitious explanation of phenomena physicists would still be puzzling over two centuries later. “Universal space, as far as we know of it, seems to be filled with a subtle fluid, whose motion, or vibration, is called light,” Franklin wrote in a letter read to the American Philosophical Society. The vibrations of light—sunlight, for example—heated objects on which the light fell by causing the particles of those objects to vibrate in turn. Franklin used the word “fire” to denote a combination of electromagnetic, kinetic, and chemical energy—a combination about which he was rather vague (and, in fact, confused). He was not sure whether this “fire” was something material or immaterial (although in this he unknowingly anticipated the Einsteinian equivalence of mass and energy). But he hit on a fundamental law of conservation of mass-energy. “Thus, if fire be an original element, or kind of matter, its quantity is fixed and permanent in the world. We cannot destroy any part of it, or make addition to it; we can only separate it from that which confines it, and so set it at liberty, as when we put wood in a situation to be burnt; or transfer it from one solid to another, as when we make lime by burning stone, a part of the fire dislodged from the wood being left in the stone.”

As always he mixed practical matters with the theoretical. Michel Guillaume Jean de Crèvecoeur, the author (under the pseudonym J. Hector St. John) of the
Letters from an American Farmer,
wrote for advice on the establishment of a packet service between France and America.

Franklin offered suggestions on the number of vessels necessary to maintain monthly service (five: four in regular service, one for backup), and on design. He had read of Chinese boats whose interiors were divided into separate watertight sections, and he urged Crèvecoeur to construct his boats similarly. “In which case if a leak should happen in one apartment, that only would be affected by it, and the others would be free; so that the ship would not be so subject as others to founder and sink at sea. This being known would be a great encouragement to passengers.” With his letter he enclosed a map of the Atlantic Ocean showing the Gulf Stream as charted by himself and others.

In a concession to advancing age Franklin had taken to using two sets of eyeglasses, one for close work, the other to see things at a distance. This was never convenient, but Franklin found it particularly irksome in traveling, when he would shift his gaze from a book or paper he was reading to a distant object he wished to observe. After considering the matter for some time, he directed his optician to take one pair of each of his spectacles and cut the lenses in half horizontally. Two each of these half-lenses were then fitted together in a single set of wire frames, with the farsighted halves on top and the nearsighted on the bottom. “By this means,” he explained, “as I wear my spectacles constantly, I have only to move my eyes up or down, as I want to see distinctly far or near, the proper glasses being always ready.” The invention brought an unexpected bonus. “This I find more particularly convenient since my being in France, the glasses that serve me best at table to see what I eat, not being the best to see the faces of those on the other side of the table who speak to me; and when one’s ears are not well accustomed to the sounds of a language, a sight of the movements in the features of him that speaks helps to explain; so that I understand French better by the help of my spectacles.”

What Franklin
called his “double spectacles” (others would call them “bifocals”) assisted his observation of the most celebrated invention of the last two decades of the eighteenth century. For millennia men and women had watched clouds waft across the sky, many wondering what held those mountains of vapor aloft. In the early 1780s the Montgolfier brothers, sons of the famous papermaker Peter Montgolfier of Annonay, attempted to duplicate nature’s feat by capturing a cloud in a light bag, which was then carried aloft. Their cloud consisted not of
water vapor but of smoke from burning straw, yet it served the purpose, carrying the brothers’ paper bag high into the air. Tickled, they graduated to larger bags, or balloons, sewn of linen or silk impregnated with a sealant, and experimented with other forms of lift, including “inflammable air,” or hydrogen.

Ballooning became an overnight sensation. The summer of 1783 saw numerous variants of the basic concept; these drew large crowds in Paris. Franklin recorded an August launch.

Not less than five thousand people were assembled to see the experiment, the Champ de Mars being surrounded by multitudes, and vast numbers on the opposite side of the river. At five o’clock notice was given to the spectators, by the firing of two cannon, that the cord was about to be cut. And presently the globe was seen to rise, and that as fast as a body of twelve feet diameter, with a force of only thirty-nine pounds, could be supposed to move the resisting air out of its way. There was some wind, but not very strong. A little rain had wet it, so that it shone and made an agreeable appearance. It diminished in apparent magnitude as it rose, till it entered the clouds, when it seemed to me scarce bigger than an orange, and soon after became invisible, the clouds concealing it.

The crowd went home well pleased; the balloon eventually landed in a field outside a village whose inhabitants, uninformed of the science involved, mistook the luminous globe for a monster and attacked it with stones, scythes and knives, rending it irreparably.

Weeks later another balloon went up from Versailles. Hot air lifted this one; suspended beneath the sack was a basket holding a sheep, a duck, and a rooster. The unwitting aeronauts survived their flight in fine health (a wing wound to the rooster was attributed to a prelaunch kick from the sheep).

If animals could fly, so could humans. On December 1 Franklin joined thousands of others to witness the momentous event. As he recorded:

All Paris was out, either about the Tuileries, on the quays and bridges, in the fields, the streets, at the windows, or on the tops of houses, besides the inhabitants of all the towns and villages of the environs. Never before was a philosophical experiment so magnificently attended.

Some guns were fired to give notice that the departure of the great balloon was near, and a small one was discharged, which went to an amazing height, there being but little wind to make it deviate from its perpendicular course, and at length sight of it was lost.

Means were used, I am told, to prevent the great balloon’s rising so high as might endanger its bursting. Several bags of sand were taken on board before the cord that held it down was cut, and the whole weight being then too much to be lifted, such a quantity was discharged as to permit its rising slowly….

Between one and two o’clock, all eyes were gratified with seeing it rise majestically from among the trees, and ascend gradually above the buildings, a most beautiful spectacle. When it was about two hundred feet high, the brave adventurers held out and waved a little white pennant, on both sides their car, to salute the spectators, who returned loud claps of applause….

When it arrived at its height, which I suppose might be three or four hundred toises [fathoms], it appeared to have only horizontal motion. I had a pocket-glass, with which I followed it, till I lost sight, first of the men, then of the car, and when I last saw the balloon, it appeared no bigger than a walnut.

The commencement of flight carried humanity into what Franklin predicted would be “a new epoch.” Public expectations were readily raised—and as easily dashed. A Dutch admirer of Franklin, Jan Ingenhousz, wrote for specifics, with a mind toward launching balloons himself. Franklin included a warning with the information. “It is a serious thing to draw out from their affairs all the inhabitants of a great city and its environs, and a disappointment makes them angry. At Bordeaux lately a person pretended to send up a balloon, and received money from many people, but not being able to make it rise, the populace were so exasperated that they pulled down his house and had like to have killed him.” (Franklin’s grandson Benjamin Bache, now thirteen and on leave from studies in Switzerland, recorded something similar in Paris after a balloon caught fire and failed to ascend. “The people were furious and threw themselves upon the balloon, and tore it in pieces, each one carrying off a sample, some large enough to make a mattress; and I believe the authors would have been subjected to the same fate if they had not been escorted by a detachment of French guards.”) When skeptics derided the
new invention as a mere toy, of no practical use, Franklin uttered a
mot
that quickly circulated throughout Europe. What good was a balloon? demanded one critic. “What good is a newborn baby?” Franklin replied.

As one recently responsible for making war and peace, Franklin was intrigued by the possibility that balloons might become instruments of the former—and thereby of the latter. Seventeen decades before the development of the theory of nuclear deterrence, Franklin identified its essence in the discovery of balloon flight. “Convincing sovereigns of the folly of wars may perhaps be one effect …” he wrote, “since it will be impracticable for the most potent of them to guard his dominions. Five thousand balloons, capable of raising two men each, could not cost more than five ships of the line, and where is the prince who can afford so to cover his country with troops for its defence as that ten thousand men descending from the clouds might not in many places do an infinite deal of mischief before a force could be brought together to repel them?”