Throughout his life, Ben Franklin continued to ask questions. Why? How? What? Why does salt dissolve in water? Why are voyages from America to England so much faster than voyages from England to America? How do crabs reproduce? How do ants tell each other where to find food? What causes earthquakes?
Two years before his retirement, Ben had tried to find an answer to the old Junto question, “How can smoky chimneys be cured?” Heating a home in the 1700s was dirty and inefficient. Most colonial fireplaces spewed black smoke into the room. Meanwhile, most of the heat escaped up the chimney.
Franklin designed a stove he hoped would solve these problems. A wood fire in the metal stove would heat the air in an inner metal box. This warm air would then flow out through vents in the side of the stove. But the smoke would be carried out a pipe and up the chimney.
Franklin was very proud of his “Pennsylvania Fireplace.” In his advertisements, he claimed that it made the room “twice as warm with a quarter of the wood.” He could have made a lot of money from his invention. But he refused to patent it. He wished to serve others “freely and generously,” through his inventions.
In order to satisfy his curiosity about the natural world, Franklin dove into every science book the Library Company ordered. He had always been interested in the sciences—in chemistry, mathematics, astronomy, biology. But nothing captured his curiosity the way electricity did.
Not much was known about electricity in the early 1700s. Somehow, people realized, “electrical fire” could be caused by rubbing glass or certain other materials. Sparks would fly out—hiss, crackle, pop! And if someone touched the electrified object, he or she could get a small shock—or a big one. Sometimes the jolt would be so great the person would be weak or sore for days.
Traveling showmen used electrical fire to entertain. First they filled a glass container with water, coated it with metal foil, and stopped it up with a cork. A metal rod stuck through the cork was set in the water. This was called a Leyden jar. After the jar was charged with a spark, anyone who touched it would get an electric shock.
In one famous demonstration, a French scientist in Louis XV’s court sent a jolt of electricity through 180 soldiers holding hands. As the force passed through them, they all jumped at once. The audience loved it. The king laughed uproariously when the scientist gave the same demonstration with 800 monks.
Franklin had his first opportunity to see the mysterious force in action when he visited Boston in 1743. There a Scottish physician named Dr. Archibald Spencer was thrilling audiences with his electrical demonstrations.
Spencer would rub a long brass tube with his hand, then hold it near pieces of gold leaf. The gold pieces would whirl wildly in the air. Some of them leaped toward the tube—others darted away.
Then, in the climax of the show, Spencer suspended a young boy from the ceiling with silken ropes.
The audience held its breath.
Dr. Spencer rubbed a glass tube near the boy’s feet. The boy’s hair stood on end. Sparks shot from his face and hands.
Franklin held his knuckles out towards one of the boy’s fingers. Flash! A spark crackled between them.
Franklin was intrigued. I wish my friends could see this, he thought. He invited Dr. Spencer to come to Philadelphia, and advertised the lectures in the Gazette. On May 3, 1744, an announcement read: “A course of experimental philosophy [science] begins in the Library-Room, next Monday at five o’clock in the afternoon.”
By 1744, the Library Company had moved to the second floor of Philadelphia’s new State House, which later became known as Independence Hall. The rooms housed a collection of more than 400 books and a mini-museum. Thomas Penn’s print of an orrery had been the first exhibition. Then came an air-pump from John Penn. Other donors sent fossils, dead animals preserved in glass jars, tanned skins, and all sorts of other strange and interesting objects. The Company owned both a microscope and a telescope, which were often borrowed by scientists.
The Library Company was the perfect place to hold scientific lectures. It was also the perfect place for Franklin to perform his own first experiments in electricity.
Franklin asked the Library’s agent in London, Peter Collinson, to send any information he had on electricity. In 1747, Collinson shipped the Library a long glass tube and instructions for using it. Then Franklin and his friends started their experiments. During the winter of 1748–49, Franklin lived and dreamed electricity.
Oh, how the sparks flew! Franklin and the others rubbed the glass jar and drew sparks from the gilt frames of mirrors or the gilded covers of books. They lit candles and alcohol with electric sparks, and passed electric kisses back and forth between the gentlemen and the ladies.
When they got tired of rubbing the glass by hand, they built a little machine. As they turned the handle, a glass globe spun and rubbed against the pad, glittering merrily away.
Franklin decided to have some fun. He made a little spider of burnt cork, with spindly linen legs. Inside the cork he placed a bit of lead. Then he hung the spider from a bit of silk thread and waited for visitors.
When anyone approached the table—the spider leapt up! The onlookers would jump back, startled. Back and forth the electric spider sprang between an electrified jar on one side of a table and a wire on the other. It looked alive!
Another time, Franklin electrified a painting of King George II. If someone touched his gilded crown, they got a “high-treason” shock!
Such “electrical amusements” could be really dangerous. Once Franklin himself was nearly electrocuted. He linked two jars together, and touched one of them by mistake. Flash! He felt a “universal blow from head to foot throughout the body.” His chest was sore for a week afterward. Luckily, Franklin had taken the shock through his hand. If it had come through his head, he realized, he might not still be alive to tell the story.
Playing with electricity was not all fun and games. Franklin made some very important discoveries and invented new ways to describe what he had observed:
X Sometimes objects with an electric charge attracted other objects. Sometimes they pushed them away. Electricity, Franklin decided, must contain equal amounts of plus and minus charges. Electricity was either positive or negative.
X Some materials, such as metal or water, carried the electrical charge easily. These were conductors. Other materials, such as wax or silk, did not carry the electric charge. They were insulators.
X If charged glass and lead plates were wired together, electricity could be stored for later use. These Franklin called electrical batteries.
X Electricity was attracted to pointed objects, such as metal rods. This observation would lead to one of Franklin’s most famous inventions.
After a winter of electrical amusements, Franklin and his friends decided to have an electrical party. They drank from electrified beakers. They also used an electric shock to kill a turkey for their dinner. The turkey meat, Franklin wrote, was “uncommonly tender.”
Franklin sent news of his experiments to Peter Collinson in England. Collinson, in turn, read his letters to the most important scientific organization in England, the Royal Society. Everyone began to speak of this clever American.
Ben thought that what he had learned might help other scientists make still more discoveries. So in 1751 he put the letters together into an eighty-six-page pamphlet and published it. Experiments and Other Observations on Electricity Made at Philadelphia in America by Mr. Benjamin Franklin was an immediate hit on both sides of the Atlantic.
Franklin was having the time of his life. Yet he worried that in all his experimentation, he had been able “to discover nothing in the way of use to mankind.”
He was about to dream up one of the most useful inventions of all time!