Benjamin Franklin: An American Life (19 page)

However, on his retirement, and intermittently over the next decade or so, he would occasionally fancy himself a refined gentleman. In his groundbreaking study
The Radicalism of the American Revolution,
historian Gordon Wood calls him “one of the most aristocratic of the founding fathers.” That assessment is perhaps a bit too sweeping or stretches the definition of aristocrat, for even during the years right after his retirement Franklin eschewed most elitist pretensions and remained populist in most of his local politics. But his retirement did indeed usher in a period in his life when he had aspirations to be, if not part of the aristocracy, at least, as Wood says, “a gentleman philosopher and public official” with a veneer of “enlightened gentility.”
²⁶

Franklin’s ambivalent flirtation with a new social status was captured on canvas when Robert Feke, a popular self-taught painter from Boston, arrived in Philadelphia that year. He produced the earliest known portrait of Franklin (now at Harvard’s Fogg Art Museum), and it shows him garbed as a gentleman with a velvet coat, ruffled shirt, and wig. Yet, compared to Feke’s other subjects that year, Franklin had himself portrayed in a rather simple way, devoid of social ostentation. “He is represented in an almost painfully plain and unpretentious manner,” notes art historian Wayne Craven, an expert on colonial portraiture. “Franklin’s plainness is not accidental: both the portrait painter and his subject would have agreed that this was the most appropriate way to represent a member of colonial mercantile society who was successful, but not actually wealthy.”

Franklin was not aspiring, by his retirement, to become merely an idle gentleman of leisure. He left his print shop because he was, in fact, eager to focus his undiminished ambition on other pursuits that beckoned: first science, then politics, then diplomacy and statecraft. As Poor Richard said in his almanac that year, “Lost time is never found again.”
²⁷

Philadelphia, 1744–1751

Even when he was young, Franklin’s intellectual curiosity and his Enlightenment-era awe at the orderliness of the universe attracted him to science. During his voyage home from England at age 20, he had studied dolphins and calculated his location by analyzing a lunar eclipse, and in Philadelphia he had used his newspaper, almanac, the Junto, and the philosophical society to discuss natural phenomena. His scientific interests would continue throughout his life, with research into the Gulf Stream, meteorology, the earth’s magnetism, and refrigeration.

His most intense immersion into science was during the 1740s, and it reached a peak in the years right after he retired from business in 1748. He had neither the academic training nor the grounding in math to be a great theorist, and his pursuit of what he called his “scientific amusements” caused some to dismiss him as a mere tinkerer. But during his life he was celebrated as the most famous scientist alive, and recent academic studies have restored his place in the scientific pantheon. As Harvard professor Dudley Herschbach declares, “His work on electricity was recognized as ushering in a scientific revolution comparable to those wrought by Newton in the previous century or by Watson and Crick in ours.”
¹

Franklin’s scientific inquiries were driven, primarily, by pure curiosity and the thrill of discovery. Indeed, there was joy in his antic curiosity, whether it was using electricity jolts to cook turkeys or whiling away his time as Assembly clerk by constructing complex “magic squares” of numbers where the rows, columns, and diagonals all added up to the same sum.

Unlike in some of his other pursuits, he was not driven by pecuniary motives; he declined to patent his famous inventions, and he took pleasure in freely sharing his findings. Nor was he motivated merely by his quest for the practical. He acknowledged that his magic squares were “incapable of useful application,” and his initial interest in electricity was prompted more by fascination than a quest for utility.

He did, however, always keep in mind the goal of making science useful, just as Poor Richard’s wife had made sure that he did something practical with all his old “rattling traps.” In general, he would begin a scientific inquiry driven by pure intellectual curiosity and then seek a practical application for it.

Franklin’s study of how dark fabrics absorb heat better than bright ones is an example of this approach. These experiments (which were begun in the 1730s with his Junto colleague Joseph Breintnall, based on the theories of Isaac Newton and Robert Boyle) included putting cloth patches of different colors on snow and determining how much the sun heated each by measuring the melting. Later, in describing the experiments, he turned his mind to the practical consequences, among them that “black clothes are not so fit to wear in a hot sunny climate” and that the walls of fruit sheds should be painted black. In reporting these conclusions, he famously noted: “What signifies philosophy that does not apply to some use?”
²

A far more significant instance of Franklin’s application of scientific theory for practical purpose was his invention, in the early 1740s, of a wood-burning stove that could be built into fireplaces to maximize heat while minimizing smoke and drafts. Using his knowledge of convection and heat transfer, Franklin came up with an ingenious (and probably too complex) design.

The stove was constructed so that heat and smoke from the fire rose to warm an iron plate on top, then were carried by convection down a channel that led under the wall of the hearth and finally up through the chimney. In the process, the fire heated an inner metal chamber that drew clean cool air up from the basement, warmed it, and let it out through louvers into the room. That was the theory.

In 1744, he had a fellow Junto member who was an ironworker manufacture the new stove, and he got two of his brothers and several other friends to market them throughout the northeast. The promotional pamphlet Franklin wrote was filled with both science and salesmanship. He explained in detail how warm air expands to take up more space than cold, how it is lighter, and how heat radiates whereas smoke is carried only by air. He then included testimonials about his new design and touted that it minimized cold drafts and smoke, thus reducing the chance of fevers and coughs. It would also save on fuel, he advertised.

The new Pennsylvania Fireplaces, as he called them, were initially somewhat popular, at £5 apiece, and papers around the colonies were filled with testimonials. “They ought to be called, both in justice and gratitude, Mr. Franklin’s stoves,” declared one letter writer in the
Boston Evening Post.
“I believe all who have experienced the comfort and benefit of them will join with me that the author of this happy invention merits a statue.”

The governor of Pennsylvania was among the enthusiastic, and he offered Franklin what could have been a lucrative patent. “But I declined it,” Franklin noted in his autobiography. “As we enjoy great advantages from the invention of others, we should be glad of an opportunity to serve others by any invention of ours, and this we should do freely and generously.” It was a noble and sincere sentiment.

An exhaustive study by one scholar shows that Franklin’s design eventually proved less practical and popular than he hoped. Unless the chimney and lower channels were hot, there was not enough convection to keep the smoke from being forced back into the room. That made getting started a problem. Sales tapered off, manufacturing ceased within two decades, and most models were modified by their owners to eliminate the back channel and chamber. Throughout the rest of his life, Franklin would refine his theories about chimney and fireplace designs. But what is today commonly known as the Franklin Stove is a far simpler contraption than what he originally envisioned.
³

Franklin also combined science and mechanical practicality by devising the first urinary catheter used in America, which was a modification of a European invention. His brother John in Boston was gravely ill and wrote Franklin of his desire for a flexible tube to help him urinate. Franklin came up with a design, and instead of simply describing it he went to a Philadelphia silversmith and oversaw its construction. The tube was thin enough to be flexible, and Franklin included a wire that could be stuck inside to stiffen it while it was inserted and then be gradually withdrawn as the tube reached the point where it needed to bend. His catheter also had a screw component that allowed it to be inserted by turning, and he made it collapsible so that it would be easier to withdraw. “Experience is necessary for the right using of all new tools or instruments, and that will perhaps suggest some improvements,” Franklin told his brother.

The study of nature also continued to interest Franklin. Among his most noteworthy discoveries was that the big East Coast storms known as northeasters, whose winds come from the northeast, actually move in the opposite direction from their winds, traveling up the coast from the south. On the evening of October 21, 1743, Franklin looked forward to observing a lunar eclipse he knew was to occur at 8:30. A violent storm, however, hit Philadelphia and blackened the sky. Over the next few weeks, he read accounts of how the storm caused damage from Virginia to Boston. “But what surprised me,” he later told his friend Jared Eliot, “was to find in the Boston newspapers an account of the observation of that eclipse.” So Franklin wrote his brother in Boston, who confirmed that the storm did not hit until an hour after the eclipse was finished. Further inquiries into the timing of this and other storms up and down the coast led him to “the very singular opinion,” he told Eliot, “that, though the course of the wind is from the northeast to the southwest, yet the course of the storm is from the southwest to the northeast.” He further surmised, correctly, that rising air heated in the south created low-pressure systems that drew winds from the north. More than 150 years later, the great scholar William Morris Davis proclaimed, “With this began the science of weather prediction.”
⁴

Dozens of other scientific phenomena also engaged Franklin’s interest during this period. For example, he exchanged letters with his friend Cadwallader Colden on comets, the circulation of blood, perspiration, inertia, and the earth’s rotation. But it was a parlor-trick show in 1743 that launched him on what would be by far his most celebrated scientific endeavor.

On a visit to Boston in the summer of 1743, Franklin happened to be entertained one evening by a traveling scientific showman from Scotland named Dr. Archibald Spencer. (In his autobiography, Franklin gets the name and year wrong, saying it was a Dr. Spence in1746.) Spencer specialized in amazing demonstrations that verged on amusement shows. He depicted Newton’s theories of light and displayed a machine that measured blood flow, both interests of Franklin’s. But more important, he performed electricity tricks, such as creating static electricity by rubbing a glass tube and drawing sparks from the feet of a boy hanging by silk cords from the ceiling. “Being on a subject quite new to me,” Franklin recalled, “they equally surprised and pleased me.”

In the previous century, Galileo and Newton had demystified gravity. But that other great force of the universe, electricity, was understood little better than it had been by the ancients. There were people, such as Dr. Spencer, who played with it to perform spectacles. The Abbé Nollet, court scientist to France’s King Louis XV, had linked 180 soldiers and then 700 monks and made them jump in unison for the court’s amusement by sending through them a jolt of static electricity. But Franklin was the perfect person to turn electricity from a parlor trick into a science. That task demanded not a mathematical or theoretical scholar, but instead a clever and ingenious person who had the curiosity to perform practical experiments, plus enough mechanical talent and time to tinker with a lot of contraptions.

A few months after Franklin returned to Philadelphia, Dr. Spencer came to town. Franklin acted as his agent, advertised his lectures, and sold tickets from his shop. His Library Company also received, early in 1747, a long glass tube for generating static electricity, along with papers describing some experiments, from its agent in London, Peter Collinson. In his letter thanking Collinson, Franklin was effusive in describing the fun he was having with the device: “I never was before engaged in any study that so totally engrossed my attention.” He commissioned a local glassblower and silversmith to make more such gadgets, and he enlisted his Junto friends to join in the experimenting.
⁵

Franklin’s first serious experiments involved collecting an electric charge and then studying its properties. He had his friends draw charges from the spinning glass tube and then touch each other to see if sparks flew. The result was the discovery that electricity was “not
created
by the friction, but
collected
only.” In other words, a charge could be drawn into person A and out of person B, and the electric fluid would flow back if the two people touched each other.

To explain what he meant, he invented some new terms in a letter to Collinson. “We say B is electrised
positively;
A
negatively:
or rather B is electrised
plus
and A
minus.”
He apologized to the Englishman for the new coinage: “These terms we may use until your philosophers give us better.”

In fact, these terms devised by Franklin are the ones we still use today, along with other neologisms that he coined to describe his findings: battery, charged, neutral, condense, and conductor. Part of Franklin’s importance as a scientist was the clear writing he employed. “He has written equally for the uninitiated as well as the philosopher,” the early nineteenth-century English chemist Sir Humphry Davy noted, “and he has rendered his details as amusing as well as perspicuous.”

Until then, electricity had been thought to involve two types of fluids, called vitreous and resinous, that could be created independently. Franklin’s discovery that the generation of a positive charge was accompanied by the generation of an equal negative charge became known as the conservation of charge and the single-fluid theory of electricity. The concepts reflected Franklin’s bookkeeper mentality, which was first expressed in his London “Dissertation” positing that pleasure and pain are always in balance.

It was a breakthrough of historic proportions. “As a broad generalization that has withstood the test of 200 years of fruitful application,” Harvard professor I. Bernard Cohen has pronounced, “Franklin’s law of conservation of charge must be considered to be of the same fundamental importance to physical science as Newton’s law of conservation of momentum.”

Franklin also discovered an attribute of electrical charges—“the wonderful effects of points”—that would soon lead to his most famous practical application. He electrified a small iron ball and dangled a cork next to it, which was repelled based on the strength of the ball’s charge. When he brought the tip of a pointed piece of metal near the ball, it drew away the charge. But a blunt piece of metal did not draw a charge or spark as easily, and if it was insulated instead of grounded, did not draw a charge at all.

Franklin continued his experiments by capturing and storing electric charges in a primitive form of capacitor called, after the Dutch town where it was invented, a Leyden jar. These jars had a metal foil on the outside; on the inside, separated from the foil by the glass insulation, was lead or water or metal that could be charged up through a wire. Franklin showed that when the inside of the jar was charged, the outside foil had an equal and opposite charge.