Early Sparks - Edison and the Electric Chair: A Story of Light and Death - Mark Essig

Edison and the Electric Chair: A Story of Light and Death - Mark Essig (2005)

Chapter 1. Early Sparks

THE ANCIENT GREEKS were the first to record the observation that amber, after being rubbed, attracted bits of straw or cloth. Around 1600 the Englishman William Gilbert noted that materials such as diamond and glass shared amber's attractive qualities. He coined a new word, electric, based on elektron, Greek for amber. An electric was a substance that, when rubbed, drew light objects to itself; electricity was the property shared by these substances.1

After Gilbert the study of electricity languished for a century or so until it was taken up by members of London's Royal Society, a new association devoted to the study of the natural world. Using hollow glass tubes thirty inches long and one inch in diameter, Royal Society members produced the strongest electrical effects ever witnessed. In 1729 Stephen Gray, an experimenter with the society, corked the ends of his tube to keep dust from being sucked inside. After rubbing the glass, he noticed to his surprise that feathers were attracted to the cork as well as to the glass. The "attractive Virtue," as he put it, had been "communicated" from the glass to the cork. Curious to see how far this communication would extend, Gray attached ordinary thread to the cork, tied a shilling to the string, and found that the coin attracted feathers. He extended the string and tied on more objects—a piece of tin, an iron poker, a copper teakettle, various vegetables—and found that all became electrified. Gray attached thirty-two feet of thread to the corked end of the glass tube, tied a billiard ball to the other end of the string, and dangled it out a window. When he rubbed the glass, he found that the billiard ball still proved attractive.

Abandoning a plan to drop a string from the cupola of St. Paul's Cathedral, Gray decided to proceed horizontally. He snaked a long piece of iron wire along the ceiling of his workroom, suspending it from the beams with pieces of string. When he touched the wire with the rubbed glass wand, however, the attractive virtue did not communicate to the far end. Gray thought the string suspenders might be too thick, so he tried silk, which worked beautifully. Equally thin brass, however, failed, leading Gray to conclude that success depended upon the supports "being Silk, and not upon their being small." The differences between silk and brass wire raised the question of which objects could be supports and which receivers. (Before long another experimenter started calling these two classes conductors and insulators.) To test the electrical properties of the human body, Gray persuaded an orphan boy to allow himself to be suspended horizontally from the ceiling, supported at his chest and thighs by stout loops of silk. Gray rubbed his glass tube, touched it to the lad's feet, and found that he attracted feathers to his fingers.2

Philosophers at the time believed that electricity—as well as light, heat, and magnetism—consisted of exquisitely fine "fluids" that passed through ordinary matter. The electrical phenomena of attraction and repulsion were thought to be caused by jets of subtle fluids blowing into and out of tiny pores in larger objects. The public, however, was less concerned with theories of electricity than with the thrilling effects it produced. Members of polite society in the eighteenth century flocked to scientific lecture-demonstrations, where they learned about planetary motion, the shape of the Earth, and the size of the solar system. Newtonian physics could be a bit dull, but a suspended human body attracting objects to its fingers—that was magic. Electrical displays swept Europe in the 1740s, and a French entrepreneur sold electrical kits that included a glass wand for rubbing, light objects for attracting, and thick silk cords for hanging human conductors. In darkened rooms lecturers drew sparks—"electrical fire"—from the noses of suspended men.


In the electrical craze of the 1740s, "human conductors" were sometimes suspended from the ceiling by silk cords and charged with electricity.

Experimenters in Germany produced more flamboyant effects. They replaced the glass wand with a spinning globe and used a "rubber" of leather or paper to excite it. They also suspended prime conductors—usually a sword or gun barrel—near the globe to collect the charge. Experimenters were soon killing flies with shocks from their fingers and showcasing the "Venus electrificata," a woman whose kisses threw sparks. When a glass of brandy was lifted toward the lips of a charged man, the spark from his nose set the liquor aflame.3

Human conductors began to complain that these shocks were unpleasant, but they did not know true pain until they experienced another new device. In 1746 Pieter van Musschenbroek of the University of Leyden attempted to produce electricity with a glass globe and then store it in a jar of water. He attached a wire to the gun barrel that served as his prime conductor and placed the wire's end in a water-filled glass jar. While an assistant spun and rubbed the glass globe, Musschenbroek held the water jar in his hand and reached toward the gun barrel. The shock knocked him to the floor. Unwittingly, he had invented what became known as the Leyden jar, which could build up charges of remarkable strength. One experimenter used the jar to knock children off their feet, and another reported that his wife could not walk for a time after being shocked. The discharge (a new word coined to describe the Leyden jar shock) could be communicated through several people. In France, to amuse the king, a powerful Leyden jar was discharged first through a circle of 140 courtiers, then through 180 gendarmes. Two hundred Cistercians felt the jolt in their Paris monastery and leaped toward the heavens in unison. The experimenters found they could make the shocks even more powerful by linking several jars to form a battery. One man wrote, "Would it not be a fatal surprise to the first experimenter who found a way to intensify electricity to an artificial lightning, and fell a martyr to his curiosity?"4

ATMOSPHERIC LIGHTNING—the type that shot from the heavens—posed greater dangers and provoked nearly as much curiosity. According to prevailing theories, lightning resulted from colliding clouds or some unknown chemical reaction in the atmosphere, but no one knew for sure what it was. A few believed that it was composed of electrical fluid—the spark and crackle of electricity made the connection obvious—but this theory had not been proved. Inspired by an itinerant lecturer, the Philadelphia printer Benjamin Franklin began experimenting with electricity in 1745. A few years later he proposed an experiment to "determine the Question, Whether the Clouds that contain Lightning are electrified or not." He attached a silk handle to the end of a kite string and tied a key where silk and string met. Standing in a doorway to keep himself and the silk dry, he flew the kite into a "Thunder Gust." Electricity tingled down the wet string, and Franklin drew sparks from the key first with his knuckle, then with his tongue.5*

Many experimenters in Europe tried variations on Franklin's experiment. Most survived the dangerous test unscathed, either through dumb luck or because they carefully insulated themselves from the lightning. In 1753, however, Georg Wilhelm Richmann, a German working in St. Petersburg, drew a bolt directly through his body. He became the first man to sacrifice his life in the pursuit of electrical knowledge.6

Franklin himself knew something about death from electricity. Not long after he proposed his famous lightning experiment, he informed a friend that the discharge from a battery of two Leyden jars was "sufficient to kill common Hens outright." The birds died so quickly, he said, that "compassionate persons" might adopt it as a method of killing. Butchers could build a battery of six Leyden jars, link the battery to a chain, wrap the chain around the thighs of a turkey, and lift the bird until its head touched the prime conductor. "The animal dies instantly," Franklin wrote. He warned experimenters to be cautious. While killing turkeys, he accidentally administered the shock to himself: "It seem'd an universal Blow from head to foot throughout the Body… . My Arms and Back of my Neck felt somewhat numb the remainder of the Evening, and my Breastbone was sore for a Week after, [as] if it had been bruiz'd. What the Consequence would be, if such a Shock were taken thro' the Head, I know not." But electrical slaughter, Franklin averred, was worth the danger: "I conceit that the Birds kill'd in this Manner eat uncommonly tender."7

FRANKLIN ALSO GAVE Leyden jar shocks to people in an attempt to cure them of paralysis. Like others caught up in the electrical mania of the mid-eighteenth century, he believed that the remarkable new force could be used as a medical therapy. John Wesley, the founder of Methodism, was one of England's strongest advocates of electrical cures. Some physicians sealed a drug inside a glass wand, electrified it, and applied sparks to patients, claiming that the essence of the medicine penetrated the body along with the subtle electrical fluid. Although physicians sold electricity as a panacea capable of curing everything from constipation to venereal diseases to hysteria, most, like Franklin, focused on paralysis. Victims of the Leyden jar reported that the shocks made their muscles contract, and doctors claimed that electricity could restore paralyzed limbs.8

Electricity's ability to contract muscles also caught the attention of physiologists. A popular theory at the time held that the brain produced subtle "animal spirits" that were carried by the nerves to move the muscles of the body. Once it was found that electricity caused muscle contraction, some proposed that electrical fluid and animal spirits were one and the same—that electricity was the natural substance coursing through the nerves of animals.

In the 1780s the Bolognese physiologist Luigi Galvani was testing the effects of electricity on muscles. When he ran brass hooks through frog legs and hung them on an iron railing, he was surprised to see that the legs contracted spontaneously, without any application of the spark. He found that he could induce contractions by touching the frog leg in two places with different metals. Galvani supposed that the frog leg was a miniature Leyden jar, which he was discharging by the touch of two pieces of metal. Since there was no external source of electricity, the jolt must have come from within the frog leg—it was "animal electricity," he said, created and stored in muscle tissue.9

Galvani's results, published in 1791, did not convince everyone. Alessandro Volta, a professor of physics, claimed that the electricity that contracted Galvani's frog leg arose not within the leg itself but from the contact of brass hook and iron railing. This statement itself was controversial. All known electricity was created by rubbing glass or other insulators; Volta claimed that he could create electricity simply by bringing two different metals into contact. Volta convinced few people of this new theory of electrical generation until he created a device to demonstrate his point. He stacked multiple pairs of silver and zinc disks, placing a piece of wet cardboard between each pair. This electrical column, or pile, multiplied the effects of the individual pairs of disks and, when touched at either end, produced a palpable shock. Volta built a pile of forty pairs and gave himself a jolt through the ears: "The disagreeable sensation, and which I apprehended might be dangerous, of the shock in the brain, prevented me from repeating this experiment."10

The voltaic pile, created to quash the notion of animal electricity, had effects Volta never imagined. The pile could be used to charge Leyn den jars, which confirmed that this new electricity was similar to that produced by rubbing glass. But there were crucial differences. Previously, all electricity had been what is now called static—the buildup of a charge, followed by its transitory discharge. The pile created an electric current that flowed indefinitely and could be made stronger by adding more pairs of metal disks.

Volta's pile, described in a letter to London's Royal Society in 1800, set off a frenzy of experimentation. One man built a battery from two types of silverware, although it was more common to pair silver half crowns with zinc disks. By summer experimenters reported that when they attached two wires to a pile and ran the "galvanic current" through water, hydrogen bubbles formed on one electrode while oxygen formed a compound with the metal of the other electrode. The current, in other words, had decomposed water into its component parts, and the science of electrochemistry was born. Humphry Davy, a professor of chemistry at the Royal Institution in London, ran the current through two common substances—potash and soda—and produced tiny globules of previously unknown metals, which were named potassium and sodium.

Davy's prestige in London rested as much on his skills as a popular lecturer as on his scientific discoveries. Though important to science, electrochemistry offered little drama in the lecture hall, so Davy found ways to please his audience. In an 1809 demonstration he ran the current from a powerful battery across a small gap between two carbon rods. As the current jumped the gap, it created a brilliant, arc-shaped, blue-white light that flooded the lecture hall and astonished the crowd.11

DAVY HAD INVENTED what came to be known as the arc light. At the time it had few practical applications, since batteries powerful enough to produce the effect consumed large amounts of rare metals-silver, copper, zinc—and were therefore enormously expensive. Around 1830, however, scientists discovered a new way to produce electricity. Michael Faraday, who started his scientific career as Davy's assistant, became intrigued by a report that an electric current caused movement in a nearby compass needle. This suggested that electricity produced magnetism. Faraday wondered if the reverse was true—whether magnetism could produce electricity. In 1831 he showed that rotating a coil of conducting wire within the lines of force of a magnetic field caused a current to flow in the wire. Following Farada/s lead, instrument makers in France created the first magneto-electric generators (often shortened to magnetos), hand-cranked machines that spun coils of wire relative to magnetic fields, creating electrical current.

The coils of conducting wire in a generator were known as an armature. As figure 1 shows, when the armature was in the first half of its rotation, the current moved along the conductor in one direction, from point A to point B.But in the second half of the turn, the relationship between the coil and the north and south poles of the magnet was reversed, causing the current to flow from point B to point A. For every 360-degree turn of the coil, the current changed direction twice: from A-B to B-A, then back again. This became known as intermittent—or alternating—current.


Figure 1: First half of rotation (left): When part of the armature cuts the magnetic lines of force near the magnet's north pole, current moves up the wire and produces a positive charge at the lower slip ring. The current is transferred from the slip rings through the brushes and flows through the outside circuit in a clockwise direction. Second half of rotation (right): The same part of the armature now cuts the lines of force near the south pole, causing current to move down the wire and producing a negative charge at the lower slip ring, reversing the current flow. The frequency of current reversal depends on the speed at which the coil rotates.

Electricity so produced behaved differently from battery current, which flowed continuously in one direction. Electrochemistry-decomposing water or isolating sodium from soda, for instance-depended on one electrode remaining positive and the other negative. The same was true for electroplating, in which a brass object such as a spoon was placed in a solution of potassium cyanide in which gold had been dissolved. When an electric current was run through the solution, the spoon—which served as the negative electrode—became coated with a layer of gold. Electroplating and electrochemistry required continuous current, because the processes did not work if each electrode was alternately positive and negative, as was the case with alternating current. Magnetos created a form of electricity that appeared to be unusable.

To solve this problem, instrument makers developed a way to transform the alternating current from a generator into continuous—or direct—current, like that from a battery. This change was accomplished with a switching device called a commutator, which kept the current in the outside circuit flowing in one direction only.12

Direct-current generators proved useful for laboratory demonstrations and electroplating, but the one large mid-nineteenth-century industry that relied on electricity—telegraphy—stuck with batteries, which provided a steadier current. In the late 1830s electric telegraph systems were developed in England by W. F. Cooke and Charles Wheatstone and in the United States by Samuel F. B. Morse. In Morse's system, the transmitter consisted of a simple key that opened and closed a circuit, transmitting pulses of electricity that conveyed a message via a dot-dash code. At the receiving end, the electricity caused movement in a magnetic device attached to a pencil, which recorded dots and dashes on paper tape. These paper tape receivers soon were replaced by sounders, devices that translated the arriving pulses into clicking noises. Rather than decoding the message after the dots and dashes were printed on paper, operators listened to the coded clicks and transcribed on the fly.13

Morse built an experimental line from Baltimore to Washington, D.C., and on May 24, 1844, transmitted his telegraph's inaugural message—"What hath God wrought!" His next transmission—"Have you any news?"—proved prophetic, as within a few years a torrent of information gushed down the slender copper wires. Whereas all previous long-distance communication depended on transportation-horses, ships, or trains carrying words on paper—the telegraph carried messages at the blazing speed of electricity. Newspapers, ever eager to scoop their rivals, were quick to embrace the technology, as were railways. Trains dispatched according to timetables tended to get off schedule and collide with each other; telegraphs allowed railroad managers to coordinate traffic safely. Telegraph lines followed railroad rights-of-way, and the two technologies advanced in tandem, copper wires stretched out alongside iron rails.14

At the end of the Civil War the Western Union Telegraph Company, the industry leader, owned more than 44,000 miles of telegraph wire, more than the combined total of its two strongest rivals, American Telegraph and U.S. Telegraph. At that time long-distance transmission between cities remained the core of the industry, but new telegraph-based services began springing up rapidly—most notably, fire alarm call boxes on city streets that allowed citizens to report the location of fires, and stock and gold quotation systems that linked banks and brokerage houses with central exchanges. Competition was fierce in the young industry, and companies were eager to gain an edge through technical innovation. The situation created rich opportunities for ambitious young inventors.15

* Although Franklin was the first to propose this type of experiment, he was not the first to perform it. He described a lightning experiment in a letter published in England in 1751. In May 1752 French experimenters followed his instructions and confirmed that lightning was electrical in nature. A month or so later—probably before he had heard of the French success—Franklin flew his kite into the storm.