The First Scientific American

by Joyce Chaplin

  Descartes insisted that the configuration of the particles mattered. He observed that round objects, packed together, had spaces or channels between them. So if matter was composed of particles shaped like spheres, there must be other bits that fit the channels between them. He imagined another kind of particle shaped somewhat like a cube, one whose sides had round depressions into which spheres could fit. The spherical particles, he suggested, rotated within the channeled particles; together, they filled all available space but did so in a way that permitted them to move. Any motion could then be predicted according to this mechanical definition of matter. Things did not move in and of themselves; their physical configuration facilitated the motion.41

  Cartesianism spread over the European continent and found advocates in England. But Newton, England’s premier natural philosopher, found Descartes’s theory too hypothetical. Yes, he believed, particles were the basis of matter. And yes, motion occurred. But there was no evidence that it happened because of the movement of spheres and squashed cubes, invisible to the naked eye. If the particles could not be seen, why not leave their precise shape unspecified?

  In fact, Newton chose not to define the precise mechanism of particulate motion. His followers nevertheless inferred from what he had said about gravity that, just as a planet accelerated centripetally toward the sun, so there must be a mutual attraction between particles that generated distinct forms of matter. Motion, attraction, gravity—all three were evident in the macrocosm, and so, they very likely existed on a smaller scale. And Newton himself ventured to define, through experiment and mathematics, the size, shape, and force a particle exerted, making the particulate theory of matter into an exact science.42

  It was a stalemate. Cartesians found Newtonianism disastrously unmechanical, inasmuch as its proponents spoke glibly about unseen forces such as gravity. In return, Newtonians found Cartesianism ridiculously unproven, unable to measure the forces among particles.

  Warmed by his Pennsylvania fireplace, Franklin was a comfortable Newtonian. The chunks of wood he put on the fire, the hand that gingerly inserted the wood, the wife sitting opposite him—all were material, visible accumulations of invisible particles. The same was true of the smoke that went up the chimney and, even more invisibly, the hot air that came out of the fireplace. It took a powerful act of imagination to “see” everything as composed of particles, but that is what Franklin, following natural philosophy, was able to do.

  When he pointed out that air got lighter, or “rarified,” and bigger (“takes up more Space”) as it grew warmer, he revealed his assumption that matter was particulate. When heated, the particles that formed air moved further apart, so the substance was less dense and lighter—this was a standard explanation. Franklin was indifferent to the question of the physical shape of these particles, which identified him as Newtonian, though it was not clear (and never was) that he consciously rejected Cartesianism.43

  In his work on heat, Franklin, by accepting the idea of Newtonian particles, examined what other philosophers had termed the “imponderables.” Imponderable substances had mass but not weight. Experimenters thought these “subtle fluids” would yield clues about matter’s particulate construction. Newton had hypothesized the existence of an aether, a subtle and elastic substance that pervaded the universe; this proposition was an attempt to explain a cosmic force that caused gravity. But Newton was uneasy over his speculation, and discusssions of the aether were absent from subsequent editions of his work. But during the 1740s, when Franklin was working on his fireplace, information on Newton’s aether was posthumously publicized, and theorists offered still other imponderable substances: heat, light, magnetism, electricity. All of these were material but not perfectly or directly visible, and they included substances we now divide among liquids, gases, and currents. Moreover, they were highly malleable, even entering other substances, as heat clearly did. Newton himself had ventured that electricity might be the central force of creation, running through the light he investigated in the Opticks and the attraction he posited in Principia.44

  Franklin’s frequent references to air becoming “rarified” by heat showed that he also was thinking in terms of fluid and elastic substances. Air was fluid (smoke flowed, for instance), and it was elastic (it expanded or compressed depending on its temperature). Yet some imponderables did not behave as conventional fluids. Franklin showed a knowledge of Newton’s Opticks when he referred to the tendency of light and heat “to move in right Lines and with great Swiftness” and when he referred to “Rays of Heat” and “Rays of Light” that “shot” outward from a source, like a fire in a fireplace.45

  Franklin’s pamphlet drew on another and more obscure idea, that of an atmosphere. In the Renaissance, philosophers seemed to use the concept initially to explain a possible condition around the moon. Then they bestowed an atmosphere on the earth. By the sixteenth century, natural philosophers argued that the earth had not the concentric rings of air, water, and fire that the ancients had arranged around it but instead three layers of “air.” The nearest was warmed by the earth, the next was cooler and had clouds, and the outermost was heated by fire and again cloudless. In 1686, Edmond Halley applied Boyle’s “spring” of the air to the atmosphere, asserting that pressure varied with height and therefore with distance from the earth. The idea of an atmosphere thereafter became a way to distinguish one space from another, whether on the earth, over a town, or even around a human body. Each such space could sustain a field of unseen matter around its center.46

  Franklin took the concept indoors. His ideal of indoor comfort reflected his beliefs that nature could generate and sustain atmospheres and that the body naturally preferred some over others. He cited Martin Clare’s The Motion of Fluids to argue that a drafty room with a fire was less salubrious than one without. He pointed to Boyle’s observation that Russians stayed perfectly healthy during their ferocious winters even though they went from their highly heated houses to the frigid outdoors; in each environment, they were at a stable temperature and so did not become ill from the stark contrast in temperatures. So too, Franklin contended, would a person maintain health even when going from a heated room to a cold bath or from a warm bed to a cold room. “The Reason is,” he explained, “that in these Cases the Pores all close at once, the Cold is shut out, and the Heat within augmented.” Repeated immersion in cold after warmth would, if anything, cause the blood to be “driven round with a brisker Circulation,” aiding health the way that brisk circulation of currency aided an economy.47

  In making these analogical leaps—from body to room, from fire-place to sun, from woodpile to forests, from heat to matter—Franklin joined an ongoing effort to use natural philosophy to improve everyday life. By the time he worked on his fireplaces, he knew the work of the foremost Newtonian experimenter, the Reverend Stephen Hales. Hales not only experimented with air and circulation but also used his findings to argue about health and public welfare, much as Franklin was doing.48

  Hales described respiration and circulation within plants and animals in his Vegetable Staticks (1727) and Haemastaticks (1733). By attaching glass receivers to foliage or severed branches, Hales demonstrated that plants indeed emitted “air” as well as visible fluid. Placing mashed apple inside an air pump, he found that the air it respired weighed far more than the apple did. That discovery supported the Newtonian idea of an elastic, particulate matter, in this case compressed within the apple and then released when the fruit was smashed open. Animal circulation likewise revealed statical principles. For his hemostatic work, Hales would do an extraordinary series of bloody vivisections. In each, he tied down an animal, severed one of its arteries, and measured how high the blood would shoot in a glass tube and then ebb and finally stop.49

  Drawing insights about health and circulation from these different experiments, Hales posited that the circulation of air benefited health and that the respiration of plants created a healthy atmosphere. He argued that better circulation o
f air on ships and in hospitals would keep people healthy; Franklin proposed the same for the circulation of heat at home. Both men used experimental results to make their cases.

  Franklin had to proceed a bit more circuitously than Hales did. He had no reputation as an experimenter and could hardly assume his newspaper and almanac readers were eager to buy a philosophical pamphlet. So he disguised his experiment. He ingeniously packaged it as two products he could sell—the pamphlet and the metal parts of the Pennsylvania fireplace. The disguise was so effective that, after Franklin’s death, people thought the pamphlet only proved that its author had invented a stove. He had done that, but he had also performed an experiment in the circulation of fluids, or elastic substances composed of particles.

  The Pennsylvania fireplace was an ongoing experiment: Franklin would tinker with it for the rest of his life. In the late 1760s, he developed a hinged “sliding plate,” or damper, with which to channel the smoke or close off the fireplace when it was not in use and simply made a room drafty. By 1771, he turned the whole thing into the freestanding vase stove, or “Franklin stove,” the bulbous metal heater that survives to this day. Despite these improvements, Franklin never believed that he got things quite right. It is pleasant to envision him, even when older and grander, getting down on hands and knees to peer up his London landlady’s chimney, banging out new metal fireplace fittings, advising Scottish aristocrats about their leaky chimneys, and drifting around drafty rooms, candle in hand, to locate currents of cold air. In the meantime, the pamphlet on Pennsylvania fireplaces, with its learned apparatus, was a kind of calling card for Franklin, a way to introduce himself as an experimental natural philosopher.

  SEVEN YEARS separate Franklin’s Pennsylvanian Fire-Places and the publication of his electrical experiments in 1751. Why was the ambitious Franklin so cautious? When it came to natural philosophy, he followed Poor Richard’s advice: “Make haste slowly.” We know that Franklin will dazzle the world. But there is no use wishing we could tell him to hurry up and go fly a kite. Franklin needed the gatekeepers in the republic of letters to pay attention to him, and they had no reason to do so. Had he continued to publish himself, as with his fireplace pamphlet or the tidbits on natural science in his newspaper and almanacs, few readers beyond the middle colonies would have noticed and he, like his brother James, would now be known to a handful of specialists on early America who study the mental world of colonial printer-publishers. The way to make a real mark in the world was to proceed slowly, build up a small stock of expertise, and then place ideas deferentially before the bigwigs.

  Through a series of introductions (some fortuitous, others stage-managed), Franklin slowly inserted himself into an Atlantic network of correspondents interested in natural philosophy. For him, entry into this network was an intellectual goal—and a great deal more. He knew that all prominent colonists had friends and patrons in London, an absolute necessity for doing work in the sciences. Franklin had a friend in William Strahan, his fellow printer, but Strahan specialized in politics and political writers, not naturalists. Franklin needed to make friends who would connect him to natural philosophers in London.

  Where should he begin? Franklin knew one other place where he was known, Boston, and his first thought was to promote himself there. It was not nostalgia that prompted him but rather the fact that the Bay Colony was layered with learning. Harvard College fostered scholars of all types, and, compared to Pennsylvania, the older and still somewhat richer colony of Massachusetts could support greater importation and production of books, scientific instruments, and experts. Having fled Boston ignominiously, Franklin wanted to return as a gentleman and scholar. He hoped his family and friends would help him. He told his parents about the Philadelphia botanist John Bartram, “an intimate Friend of mine,” who would “be glad of a Correspondence with some Gentlemen of the same Taste” in Boston. A word to the right person could connect Franklin, via Bartram, to some Boston man of letters. But there is no sign that the elder Franklins managed to do this or that they even tried.50

  So Franklin used family and business visits to Boston to do this work himself. During one sojourn in the spring of 1743, he attended Archibald Spencer’s lectures on “Experimental Philosophy.” As in Europe, such demonstrations used sensation—sparks, explosions, optical illusions—to present the sciences to the public. Spencer ran through the best-known discoveries, “the Circulation of the Blood,” “Sir Isaac Newton’s Theory of Light and Colours,” and the fact “that Fire is Diffus’d through all Space,” meaning brief exhibits of electricity. These were the first demonstrations of electricity Franklin had seen—“they equally surpriz’d and pleas’d me,” he recalled. He also helped arrange for Spencer to give his lectures at the Library Company, a series he promoted both in the Pennsylvania Gazette and in the description of the lectures he printed in 1743.51

  Having introduced his colleagues to Spencer, Franklin wanted them to return the favor. The two men he had been cultivating, John Bartram and James Logan, obliged him. They led him to two important contacts: Peter Collinson in London and Cadwallader Colden in New York. Further introductions to other men of science would follow. Indeed, Franklin’s friends tended to know each other.

  For Franklin, these colonial counterparts were also potential role models and sometimes cautionary tales. He studied his peers’ strengths and weaknesses and learned a great deal. Above all, he could assess the trade-offs between doing natural history, which described things in nature (as Bartram did), or doing natural philosophy, which analyzed the universal causes of things in nature (as Logan and Colden did).

  Peter Collinson, a Fellow of the Royal Society who had extensive political connections, was looking for a colonial protégé and slowly, via other Philadelphians, made his way to Franklin. Collinson was a cloth merchant from a Quaker family who had trained himself in botany. Through his trade, he corresponded with like-minded colonists, including Joseph Breintnall, a Philadelphia merchant and one of the Junto’s founders. (“Very ingenious in many little Nick-nackeries,” Franklin remembered of Breintnall, demolishing a man who had been his elder and better for some time, “and of sensible Conversation”—a bit more generous.) At some point, Collinson asked Breintnall to introduce him to a botanically inclined Philadelphian. In short order, Bartram and Collinson became regular correspondents, and it was probably through the London merchant that Bartram exchanged letters with Linnaeus.52

  Collinson rummaged up no fewer than fifty-seven patrons who underwrote Bartram’s travels and gardening. (It was a sharp contrast to Franklin’s failure to promote Bartram locally, in his newspaper and almanac.) But however indispensable Bartram became to British men of science, they considered him a social inferior and let him know it. Even Collinson considered his client completely inept except when planted amid his plants; he gave Bartram (and his wife) clothing as well as advice about how and when to wear it, which was patronizing in both senses of the word. Bartram seemed resigned: he was the naturalist’s naturalist. His native genius with plants never transferred to other realms, and he had no desire to declare any universal principle about the vegetable world. Collinson was therefore eager to find other Philadelphia protégés. He agreed to act as agent for the Library Company (Breintnall was an original subscriber) and to arrange some of its purchases of books and equipment. Collinson would also make donations to the company. In that way, by the 1740s, he began to focus his patronage on Benjamin Franklin.53

  Franklin knew what to wear and when, and he aspired to be not Collinson’s client but rather his social and intellectual equal. To this end, he needed to produce something more important than his piece on fireplaces. This effort would require him to exchange ideas and rough drafts with his peers in the colonies, lest he disgrace himself with an ill-considered essay sent to Collinson directly. Nearly all of Franklin’s thoughts on the natural world proceeded through a series of letters. He wrote initially to friends or select correspondents, developed his ideas through continu
ed correspondence, and culminated with refined letters he would then send on to experts. Such was the case with the letters he eventually sent to Collinson to be read (he hoped) before the Royal Society.54

  Cadwallader Colden became the first link in the chain. Franklin had probably known the New York resident, by reputation, for some time. They both knew Logan and Bartram; Colden and Collinson were correspondents, and Collinson had introduced Colden to Strahan. Yet Franklin and Colden ended up having an “accedental Meeting on the Road” in Connecticut when Franklin was on his way to or from Boston in 1742.55

  Born to Scots-Irish parents, educated at the University of Edinburgh and in medicine in London, Colden had lived in Philadelphia but moved to New York in 1718, four years before Franklin arrived in Philadelphia—a near miss. When Colden failed to establish a medical practice in New York, just as he had failed in Philadelphia, he turned instead to politics as well as natural history and philosophy. He was among the original subscribers who underwrote the cost of Ephraim Chambers’s Cyclopedia, a significant and ambitious undertaking for someone in the colonies. He had particular skill in botany, and Linnaeus praised him as “Summus Perfectus,” or supremely perfect. Eventually, Colden turned over his botanical studies to his daughter, Jane, and by the early 1740s, he had moved into Newtonian mechanics, where the real action was.56

  Franklin admired the ambition. Colden was addressing the question of universal causes—gravity making stones fall in Europe and America alike—that Newton had defined. Franklin professed to Colden that he could not “but be fond of engaging in a Correspondence so advantageous to me as yours must be.” He used his 1743 plan for a learned society in Philadelphia to keep Colden, a potential corresponding member, interested in writing to him. Franklin pointed out that he and Colden were progenitors of the project, a short-lived ancestor of the American Philosophical Society. Colden had evidently advised Bartram to form the society; both Bartram and Logan passed the task to Franklin. “I tould Benjamin,” Bartram wrote Colden, “that I believed he [Logan] would not incourage” the proposed society but that they should “Jog on without him.” Logan did not, and they did, at least for a time. On a visit to New York in early 1744, Franklin left a letter for Colden, reporting that “the Society” had members (whom he listed) and held meetings; he promised future news of the meetings.57