by Jill Jonnes
For more than half a century, human knowledge and understanding of electricity progressed little further. Philosophers throughout Europe remained fascinated by electricity, and De Magnete was studied carefully and its experiments copied. But the next major electrical advance came almost unwittingly (as often happens in science), from the Lutheran mayor of Magdeburg, a small free-trading city in the Holy Roman Empire (today Germany) burned to the ground by marauding Swedes in 1631. The mayor, Otto von Guericke, was a well-educated scion of a leading family, and he devoted his middle decades to rebuilding and reviving his crushed city and retrieving through treaties its free status. The overburdened von Guericke found soothing solace, “a gate of tranquility,” in astronomy. He decided to try to replicate the earth’s sphere and study a complex system of “virtues” he believed swirled in and about it. He created a solid sulfur ball the size of an infant’s head, which he placed in a sturdy wooden frame and rotated by an attached handle. When this twirling yellow globe (later ones were far larger and incorporated more minerals) was rubbed, it became electrostatic and attracted and then repelled many light objects, typically a feather.
The convivial burgomaster enjoyed amusing his guests by walking about with a small sphere steadily propelling before him a buoyant feather, ultimately steering the feather to cling to some visitor’s nose. When the sphere really got whirling and was rubbed, it began to glow and throw off sparks. With his globe, von Guericke inadvertently showed that one could produce notable amounts of electricity, yet he did not advance actual knowledge. In Germany in the late seventeenth century, von Guericke happily made and dispensed his globe to others, but no British (or other) philosopher seems to have interested himself in its potential for electrical experiments. That did not transpire until 1709, when Englishman Francis Hawksbee, curator of instruments at the Royal Society, created a similar object, also an electrostatic machine. His was a mounted hollow glass sphere that could be cranked to high speeds and rubbed to create electricity and eventually an eerie light inside, a feat shown to great acclaim. Hawksbee thought to add a “rubber,” a short adjustable column with a stuffed leather piece that pressed steadily on the glass (in place of a hand) to provide friction. Electrostatic machines like this could generate sizable sparks and became the standard source of electricity for experiments and entertainment during the early eighteenth century.
The next true electrical advance came from Stephen Gray, a modest native of Canterbury on the Stour River, then as now home of the great Anglican cathedral. Gray was from a family of dyers, but he acquired enough education to read Latin and become a friend to the astronomer royal in Greenwich. While Gray earned his daily bread as a dyer, his inner being was dedicated to science and experiment. He sufficiently impressed the professors at Cambridge with his stargazing reports that at age forty-one they hired him to work at Trinity College’s new observatory. At the university Gray discovered the mysterious delights of electricity, but also “mercenary” flaws in his employers. He retreated to Canterbury for a few years and then sought residency at the Charterhouse in London, a day school for poor boys and a selective residence for impecunious gentlemen. Knowing well England’s continuing obsession with practical advances in sea-going, Gray assured the trustees that if admitted, he intended to devote himself to “inquiries Relating to Astronomy and navigation and might haply find out something that might be of use.”2 Whatever else Gray did in his first decade as a genteel Charterhouse pensioner, by 1729 he began to work on seeing how far he could send the “electrical vertue.” Using an electrified glass tube, he tested all kinds of substances, finding metal wire to be excellent for conveying electricity, as was plain packthread. Having succeeded in sending electricity fifty-two feet, in June of 1729 Gray repaired to the grander spaces of a wealthy friend’s country estate. There they soon transmitted electricity 765 feet and methodically worked their way through all manner of substances, hollow or solid, determining which conducted electricity well or not at all. Gray also noticed that if you suspended an iron rod pointed at both ends from silk threads and touched it with an electrified glass tube, it briefly gave off cones of light, a wondrous and memorable result. Gray further remarked that great sparks of electricity made noises not unlike that produced by thunder.
The most memorable, original, and flashy of Gray’s experiments, and one that was delightedly replicated for years, was that of the dangling Electrified Boy. On April 8, 1730, Gray constructed a stout wooden frame from which he suspended via strong silk strings—as if he were a very large bird—a forty-seven-pound boy, probably one of the Charterhouse charity students. All parts of the boy were thickly covered in nonconducting clothes, leaving only his head and hands and a few toes naked. In one outstretched hand, the boy held a wand with a dangling ivory ball. When Gray touched the boy on the backs of his naked toes with an electrified glass tube or vial, the electricity traveled to the boy’s head (where his hair stood on end) and his outstretched hands. Then three feathery-light piles of brass leaves under the boy rose up in three impressive little clouds, before sinking back down. One pile rose only to the ivory ball, showing that the electricity had continued on beyond the hand, one pile rose as high as the face, and the third rose to the bare hand, which hung lower than the head. A thrilling variation had the dangling boy stretch out his finger and touch another person. This gesture transmitted a noticeable spark and a shock, if the standing person was on a conducting material. Gray found he could also elicit sparks from the end of the boy’s nose. The presence and nature of the “electrical vertue” was thus dramatically made visible. Pensioner Gray had invaluably demonstrated to the world much about the conductive qualities of electricity. Human nature being what it is, frolicsome philosophers could not resist many amusing versions of the Electrified Boy demonstration. Men were soon bestowing electrified kisses on (literally shocked) women. One waggish French host wired the chairs at his dinner table so that his astonished guests suddenly found sparks flashing from their forks!
For the next major electrical leap forward, we move across the English Channel to the Continent. All over England and Europe in this self-proclaimed Age of Enlightenment, the sages of the day were studiously observing the natural world around them, offering up theory upon theory to explain things previously taken for granted, ignored, or explained by myths or magic. Electricity was one of the most mesmerizing and entertaining of nature’s multitude of puzzling phenomena. Up until this time, philosophers had learned from the royal physician William Gilbert that there was electricity, what he called “electrical effluvia.” From von Guericke and Hawksbee, people had learned to make and operate electrostatic machines that more efficiently produced electricity. From pensioner Stephen Gray came a serious study of which materials were conductors and then how far electricity could be conducted. In this era, even the most dedicated and serious scientists felt it was their role to provide awe-inspiring electrical demonstrations that also entertained.
At this stage, the pursuit of electrical knowledge was restricted by the limited amounts of electricity experimenters could actually generate. The first solution to storing electricity was stumbled upon in Leyden, Holland. Professor Pieter van Musschenbroek’s lawyer friend, Andreas Cuneus, had come by the laboratory to divert himself with various electrical experiments. One involved filling a jar with water and electrifying it by touching a wire sitting in the water with an electrified glass vial. Cuneus then touched the protruding wire and received a bad jolt from the stored electricity. He mentioned this to Musschenbroek, who in mid-January 1746 electrified the jar of water (via the wire) with one of his great whirling globes, not a small electrified glass vial. He wrote several days later to an academic in Paris to explain “a new but terrible experiment, which I advise you never to try yourself, nor would I, who have experienced it and survived by the Grace of God, do it again for all the kingdom of France.” Musschenbroek warned that when he touched the metal protruding from the jar, he was “struck with such force that my whole body
quivered like someone hit by lightning … the arm and entire body are affected so terribly I can’t describe it. I thought I was done for.”3 The sensational news of the Leyden jar spread like electrical wildfire, causing every other serious electrical philosopher to construct one and experience its fearsome jolts. Soon it was found that lining the jar halfway up with metal foil inside and out helped retain the electricity, while the power of several jars combined created a shock strong enough to kill a sparrow. For the first time, scientists could actually store these wondrous electrical forces.
The standard Leyden jar consisted of a squat container of thin glass encased inside and out on its lower two-thirds with a metal foil coating. A brass wire topped by a small brass ball protruded from the snug (nonconducting) cork lid and then also hung down into the water-filled jar. Electricity generated by electrostatic machines was directed into the glass jar via the ball and wire, traveling down the metal wire or, later, down a long metal chain, and then charged the metal foil and water. When a philosopher needed electricity, he touched the ball and out it flowed in a great jolt. Leyden jars could retain their electrical charge for as long as several days, depending on insulation and storage conditions.
While the philosophers in the royal societies and universities observed, measured, and cogitated on their electrical findings in respectable learned journals, they also continued to use electricity (such as it was understood) for pseudomagical entertainments and diversions. With the invention of the Leyden jar, many a traveling huckster took to charging good money to the bold and brave for a chance to experience the man-made lightning that sparked forth from the jar. At the Versailles court of Louis XV, the relentless search for novelty and amusement led the Abbé Nollet, a serious student of the electrical arts, to begin arranging spectacular electrical displays. Most memorable was the assembling of 180 gendarmes in a big circle in the Grande Gallerie, each holding the next man’s hand. Nollet, attired in powdered, coiffed peruke and a long, pinch-waisted coat with fashionable big cuffs, wished to see how far the electrical shock would travel. The electrostatic machine was revved up, charging the Leyden jar. The gendarme at the head was holding the Leyden jar. When he touched the brass ball, 179 others leaped into the air with a strange precision. “It is singular to see the multitude of different gestures,” wrote the good abbé, “and to hear the instantaneous exclamation of those surprised by the shock.”4 The king and his jaded courtiers found the leaping gendarmes both marvelous and hilarious. It was also a palpable demonstration that electricity traveled (though they could not know it) at the speed of light. Having diverted the court, Nollet satisfied his scientific soul that this was not a fluke by repeating the test first on two hundred robed Carthusian monks at their monastery in Paris and then a great circle of six hundred people at the Collège de Navarre.
The mysteries and marvels of electricity absorbed many of the brightest intellects of early-eighteenth-century Europe, but the next electrical advances emanated from a very unlikely venue, the British colonies in North America. In the attractive Quaker port city of Philadelphia, laid out in a spacious grid, Benjamin Franklin, the respected editor of the popular Poor Richard’s Almanack, had attained sufficient prosperity to devote himself largely to philosophical matters. Little involved in his printing business and not yet caught up in politics, in 1744 Franklin saw in Boston a Scottish lecturer demonstrate the popular dangling Electrified Boy. The next fall, a Quaker merchant friend in London, Peter Collinson, sent along various electrical apparatus and writings. Franklin was soon hooked. Months after European philosophers had become enthralled with the new possibilities of the Leyden jar and were hotly debating how and why it could store electrical charges, Franklin and his experimenting colleagues had one in hand. The genial Franklin, forty, his brown hair shoulder length, attired in plain breeches and long jacket, held electrical court at his small Market Street house that also served as his printing shop, library, and now laboratory.
By the spring of 1747, Franklin was writing Collinson, “I never before was engaged in any study that so totally engrossed my attention and my time as this has done lately. What with making experiments when I can be alone, and repeating them to my friends and acquaintances, who, from the novelty of the thing, come continually in crowds to see them, I have, during some months past, had leisure for little else.” Curious neighbors and strangers jammed in to watch Franklin generate electricity with his fast-turning glass cylinder, capture those flaring sparks in his Leyden jar, and then demonstrate the many puzzling ways electricity seemed to work. At one point Franklin wrote his friend in London, “If there is no other use discovered of electricity, this however is considerable, that it may make a vain man humble.”5 It was a most confounding effluvium.
In fact, Franklin made considerable strides as he applied his tremendous curiosity and intellect to understanding electricity, conducting hundreds of experiments aimed at teasing out specific electrical qualities. He also devised numerous “recreations,” including the “counterfeit spider,” a black arachnid that came “alive” as it danced about in an electrical field; a book that appeared aflame; and a most amusing electrical fish, a thin gold leaf in a tapered shape. “If you take it by the tail, and hold it at a foot or greater horizontal distance from the prime conductor, it will, when let go, fly to it with a brisk but wavering motion, like that of an eel through water.”6 Perhaps most telling of future events was a “magical” picture showing the British king wearing his crown. Those who tried to remove the crown received a notable shock. Such enterprises were both playful and instructive, and Franklin was the first to assert that there were not different kinds of electricity—as many believed—but one basic fluid with positive and negative qualities. Yet Franklin, being ever the practical soul, was “chagrined that we have been hitherto able to produce nothing in this way of use to mankind.”7
Franklin fluctuated between a humble awe at the small revelations of nature’s secrets and a giddy glee at his newfound skills. He and his merry band of electrical experimenters had sufficiently mastered the production and storage of electricity to plan a most unusual and festive dinner down by the Schuylkill River prior to dispersing for the muggy summer months. In April 1749, Franklin jovially described their plan: “A turkey is to be killed for our dinner by the electrical shock, and roasted by the electrical jack, before a fire kindled by the electrified bottle; when the health of all the famous electricians in England, Holland, France, and Germany are to be drank [sic] in electrified bumpers, under the discharge of guns from the electrical battery.”8
Like other philosophers before him, Benjamin Franklin suspected that lightning was simply a massive jolt of electricity. And by early 1750, he believed he had come up with a practical and lifesaving object that could also test out his lightning-is-electricity theory. Franklin suggested erecting tall, pointed metal poles on tall buildings to conduct the lightning down to the ground, where it would dissipate into the dirt, thus protecting the structures from fire. For the actual experiment, the lightning off these poles could be collected into Leyden jars. He explained, “The effect of [points is] truly wonderful; and, from what I have observed on experiments, I am of opinion that houses, ships, and even towers and churches may be effectually secured from the strikes of lightning by their means.”9 However, people were understandably reluctant to tempt lightning, a known creator of conflagrations, onto their property. This same year around Christmas, Franklin himself, failing to exercise caution, was knocked senseless just by man-made electricity intended to kill a turkey. Franklin described taking “a universal blow throughout my whole body from head to foot, which seemed within as well as without…. I had a numbness in my arms and the back of my neck which continued til the next morning but wore off.”10
In the next two years, Benjamin Franklin found his talents and time given over more and more to pressing public affairs. Yet he was still thinking deeply about the mysteries of electricity and in September of 1752 finally had occasion to carry out a lon
g-planned experiment. On an oppressive and muggy afternoon, as a thunderstorm began building, its angry dark clouds boiling up ominously on the horizon, Franklin and his grown son hurried through the heat out into the fields still flecked with goldenrod and wildflowers. Franklin carried a simple kite he had constructed using silk handkerchiefs and cross-sticks. At the very top of the kite, he had affixed a foot-long piece of metal wire to serve as a conductor. At the bottom, he had attached a hempen string and from that a ribbon of silk (a known nonconductor). Where the hemp and silk met, Franklin had hung a metal key. As the storm winds gusted violently through, Franklin maneuvered his kite into the air, whereupon he and his son sought shelter from the downpour in a small wooden structure. The kite raced high up into the gray clouds, while the nearby trees rocked in the storm gusts. In the distance, lightning vibrated brilliantly across the darkening sky. Franklin and his son watched the hemp, but there was no sign of electrical life. Wet and losing hope, they suddenly saw what they were looking for—the loose threads of the hempen string rising as if electrified. Franklin, knocked out by electricity one time, gingerly touched his knuckle to the metal key and saw and felt a distinct electric spark. Once the string was wet, the electricity from the passing lightning storm flowed steadily down it. Franklin was just lucky no lightning struck his kite directly. And so it was that Franklin, by this brilliant experiment, entered the pantheon of electrical giants, philosophers who signally broadened and advanced the human understanding of this powerful, puzzling, invisible energy. No more did electricians have to speculate. They now knew, thanks to Benjamin Franklin, that lightning was electricity similar to—or maybe the same as—that which men were making with their electrostatic machines. Franklin was hailed as an eighteenth-century Prometheus, one who had literally stolen fire from the heavens and lived to tell the tale.
