Benjamin Franklin was one of the most practical inventors in history. He built many devices that were designed to help improve or solve everyday problems. Some of his inventions, like bifocal glasses, are well-known, while others are more obscure. Of the numerous inventions Franklin created, he did not patent a single one. Franklin believed that “As we benefit from the inventions of others, we should be glad to share our own…freely and gladly.”
5. Glass Harmonica
In the mid-1700’s, Benjamin Franklin served as a delegate for colonial America and spent a great deal of time in London and Paris. At the time, it was popular and entertaining for musicians to perform on sets of “singing” or musical glasses. Franklin was immediately impressed with the beauty of the sound and started working on applying the principles of wet fingers on glass to his own musical device.
In 1761, Franklin completed his glass armonica. He made chords and lively melodies possible on his new instrumental invention. Working with a glassblower in London, Franklin made a few dozen glass bowls, tuned to notes by their varying size and fitted one inside the next with cork. Each bowl was made with the correct size and thickness to give the desired pitch without being filled with any water. Franklin also painted them so that each bowl was color-coded to a different note. A hole was put through the center of the glass bowls and an iron rod ran through the holes. The rod was attached to a wheel, which was turned by a foot pedal. Moistened fingers touched to the edge of the spinning glasses produced the musical sounds.
Working with a glassblower in London, Franklin made a few dozen glass bowls, tuned to notes by their varying size and fitted one inside the next with cork. Each bowl was made with the correct size and thickness to give the desired pitch without being filled with any water. Franklin also painted them so that each bowl was color-coded to a different note. A hole was put through the center of the glass bowls, and an iron rod ran through the holes. The rod was attached to a wheel, which was turned by a foot pedal. Moistened fingers touched to the edge of the spinning glasses produced the musical sounds.
The glass armonica was one of the most celebrated instruments of the 18th century. Franklin began to take his beloved armonica with him when he traveled and played popular tunes or for his audiences. Famous composers such as Beethoven and Mozart would write music for the armonica. By the 1820’s, it was nearly a forgotten instrument.
Some strange things began to be associated with the glass armonica. Some armonica players became ill and had to stop playing the instrument. They complained of muscle spasms, nervousness, cramps, and dizziness. A few listeners were also subject to ill effects; after an incident in Germany where a child died during a performance, the armonica was actually banned in a few towns. Some people thought that the high-pitched, ethereal tones invoked the spirits of the dead, had magical powers, or drove listeners mad. Others thought that lead from the crystal bowls or paint was absorbed into the musicians’ fingers when they touched the glass, causing sickness. None these claims were ever proved. Franklin himself ignored all of the controversy and continued to play the instrument until the end of his life with none of the symptoms mentioned.
4. Flexible Catheter
From ancient times, many different materials have been used to create catheters. Syrians used wooden reeds. Ancient Chinese used onion stalks. The Romans, Hindus, and Greeks all used tubes of wood or precious metal. Silver was especially valuable due to its antiseptic qualities. It was also valued because catheter users could easily bend a silver catheter to suit their specific urethral needs.
Franklin designed the device in 1757, had it made by a local silversmith, and sent it to his brother John in Boston, with a letter detailing its design and use. The catheter was made from silver wire, coiled with joints to allow flexibility, and covered with gut. He made it for his brother who suffered from “the stone”, otherwise known as a bladder stone. He more than likely used a catheter himself when he developed the same issue later in life. The flexible catheter is still used today.
3. Mapping the Gulf Stream
Benjamin Franklin and his cousin, Timothy Folger, are credited with naming and mapping the Gulf Stream for the first time. The Gulf Stream is the warm, strong ocean current that pushes northeast from the Gulf of Mexico, up the Atlantic coast, towards Europe.
While Franklin was in London (working as a deputy Postmaster General) in 1768, he received a visit from Folger who captained a merchant ship. He began to wonder why it took take British mail packet ships so much longer to reach America than it took regular merchant vessels. Folger guesses the British mail captains must not know about the Gulf Stream, with which he had become acquainted with in his earlier years as a Nantucket whaler. Franklin quoted Folger’s explanation like this:
“We are well acquainted with that stream, says he, because in our pursuit of whales, which keep near the sides of it, but are not to be met with in it, we run down along the sides, and frequently cross it to change our side: and in crossing it have sometimes met and spoke with those packets, who were in the middle of it, and stemming it. We have informed them that stemming a current, that was against them to the value of three miles an hour; and advised them to cross it and get out of it; but they were too wise to be counselled by simple American fishermen.”
Westbound British ships were losing precious time by sailing into and against the warm, strong current. Folger drew out the rough location for Franklin, who made prints, along with Folger’s directions for how to avoid what he dubbed the “Gulph Stream.”
When the American Revolution started, Franklin stopped distributing the Gulf Stream map to the British, and instead gave copies to the French, who used it to ship weapons and supplies to their American allies. After that, knowledge of the stream became hugely important for transatlantic travel.
2. The Lightening Rod
For centuries, lightning was a mystery. Many scientists of the mid-eighteenth century suspected that lightning was electricity. Thomas-François Dalibard, who translated some of Franklin’s books from English to French,performed the first experiment. On May 10, 1752, at the village of Marly-la-Ville near Paris, he set up a tall iron rod insulated from the ground with wine bottles and was successful in drawing sparks from lightning.
When Franklin did his kite experiment in Philadelphia, he succeeded in drawing sparks from thunderclouds. Franklin’s experiment is believed to have actually happened a month after the Marly-la-Ville experiment, but before he received word of its success. Philip Dray, an author on Franklin, describes the kite experiment, “Franklin carried with him a kite he had made of silk and cedar. To the top of the upright stick he had attached a sharp pointed wire that rose a foot or more above the wood. The twine leading down from the kite was attached to a silk ribbon, and on the silk ribbon dangled a key. It was important that Franklin stand indoors because the silk ribbon must remain dry…” The ribbon needed to be dry to act as an electrical insulator. Without the silk insulating the key from the ground, any electrical current would have passed straight into the ground, rather than gathering in the key. Franklin reported seeing the individual strands of hemp standing on end while waiting, and brought his knuckle close to the key, receiving a mild shock. Once rain began and wet the string, sparks started to “steam off the key to Franklin’s hand.”
With proof that lightning was indeed electricity and knowing that an iron rod could be used to attract it, Franklin erected the first lightning rod on the roof of his own house to continue tests. In his book Experiments and Observations on Electricity, he states that “an iron rod being placed on the outside of a building, from the highest part continued down into the moist earth… will receive the lightning at its upper end, attracting it so as to prevent its striking any other part; and, affording it a good conveyance into the earth, will prevent its damaging any part of the building.” This book was translated and distributed across Europe, having a huge impact on the world of science.
Franklin never patented this invention and believed that the knowledge belonged to everyone. Lightning rods helped to prevent fire and damage to structures. Franklin’s lightning rods could soon be found protecting many buildings and homes. The lightning rod constructed on the dome of the State House in Maryland was the largest “Franklin” lightning rod ever attached to a public or private building in his lifetime.
1. The Franklin Stove
In 1742, Franklin designed a cast-iron stove that was freestanding. It was able to heat rooms more efficiently than wall-bound fireplaces. It had one major flaw which was the smoke came out of the bottom of it instead of the top. even with this major flaw it was still better and safer than fireplaces. Up until then, most people had to warm their homes by building a fire in a fireplace even though it could be dangerous and required a lot of wood.
Governor Thomas offered to give Franklin a patent for the sole right of producing and selling his stove. Franklin declined the offer, believing that peoples appreciation of his stove was better then any financial reward. Franklin gave the plans and a model of his stove to Mr. Robert Grace, one of his friends, to manufacture. Grace had an iron-furnace and found the casting of the plates for these stoves in high demand and very profitable.
Franklin published a pamphlet in 1744, entitled “An Account of the new-invented Pennsylvania Fireplaces”. He described how the stove would be constructed and operated, as well as it’s advantages over other methods of warming houses. In the late 1780’s, David R. Rittenhouse redesigned the stove and added an L-shaped chimney. He called it the Rittenhouse stove but it is still known to this day as the Franklin stove.
Cast-iron stoves become increasingly popular as different manufacturers improved upon the earlier designs of Franklin and others. This led to the eventual decline of the traditional fireplace as a functional necessity for a home.