Benjamin Franklin’s Inventions

Benjamin Franklin (1706-1790) was a man of many talents. A scientist, diplomat, politician, and printer; he was also an inventor. Franklin invented the lightning rod, swim fins, odometer, and bifocals. He is perhaps best known for his experiments with electricity, which led to the development of the Franklin stove and the lightning rod. He had a restless mind and was always tinkering with new gadgets and devices. Undoubtedly, Benjamin Franklin was one of the most ingenious inventors in American history. It is difficult to imagine the eighteenth century without his many contributions.

1) The Franklin Stove

One of Benjamin Franklin’s most famous inventions was the Franklin stove in 1742. Also known as the Pennsylvania fireplace, this stove was designed to be more efficient than other stoves of its time, and it helped to heat homes faster. It is a type of metal-lined fireplace that has a hollow baffle near the rear. The stove relied on an “inverted siphon” to draw the fire’s hot fumes around the baffle. This allowed for more heat to be transferred from the fire to the room’s air while at the same time producing less smoke. However, the Franklin stove did not get many sales until it was improved by David Rittenhouse. After that, the Franklin Stove became a huge success and quickly became one of the most popular stoves in America.

2) The Lightning Rod

On June 10, 1752, Franklin conducted his famous kite experiment to prove that lightning was a form of electricity. He attached a key to his kite’s string and flew it during a thunderstorm. As the kite was hit by lightning, the charge passed through the wet string and into the key, which Franklin was holding. He proved that lightning was electrical and not, as some people believed, a random act of God. This discovery led him to invent the lightning rod.

The lightning rod—also known as the Franklin rod, a lightning attractor, or a lightning conductor—was a pointed metal rod that could be attached to the top of a building. It would conduct the electricity from a lightning strike into the ground, thus protecting the building from fire. He got this idea from watching how a pointed needle could conduct electricity away from a charged metal sphere.

Franklin speculated that, with an iron rod sharpened to a point, an electrical fire would be drawn out of a cloud quietly before it could approach enough to harm. The first lightning rod was installed on top of his own house in Philadelphia in 1752. It worked so well that soon, other buildings throughout the American colonies were topped with Franklin’s pointed lightning rods.

3) Flexible Urinary Catheter

In 1752, John Franklin, Benjamin’s older brother, suffered from kidney stones. He had to undergo the daily process of inserting a catheter through his nether region into his bladder to relieve himself of urine. At that time, catheters were made of bulky metal and as such, rigid and very painful to insert. To ease his brother’s pain, Franklin devised a catheter with a flexible tube. It had small interlocked silver rings, which allowed the tube to be bent or coiled without collapsing. This made it much easier to insert and, therefore, less painful. There were also holes on the sides of the catheter to allow the urine to drain freely. After some help from a silversmith, he sent his new-and-improved catheter to his brother with instructions on how to use it. The urinary catheter is still in use today, and though it has been improved and modernized, the basic design remains the same.

4) Bifocals

Another one of Benjamin Franklin’s famous inventions is bifocals. Bifocals are glasses with two lenses of different strengths. The top lens is for distance and the bottom lens is for reading. Franklin invented them in 1784 after he got tired of having to switch between two pairs of glasses, one for reading and one for distance. He loved reading but developed myopia (near-sightedness) and hyperopia (far-sightedness) as he grew older.

Franklin had the lenses from his two sets of glasses cut in two horizontally and mounted back into spectacle frames, with the lens for reading and other close work at the bottom and the lens for distance at the top. In a letter to his friend George Whatley, Benjamin wrote that he was happy he invented the bifocals because it makes his eyes “useful to [him] as ever they were.” At that time, he called these lenses the “double spectacle”. They were not called bifocals until much later. Nevertheless, this invention was a game-changer for people who needed help with both their near and far vision.

5) Armonica

One of Benjamin Franklin’s lesser-known inventions is the armonica, but in his words, it was the one that gave him “the greatest personal satisfaction”. Named after the Italian word for “harmony”, the armonica is a musical instrument that produces sound by means of applying friction to glass bowls of different sizes. It consists of a series of 37 glass bowls, each with a different diameter, that is mounted on a horizontal spindle. The spindle is rotated by a foot-operated treadle, much like a spinning wheel.

The armonica was invented in 1761 and was inspired by European musicians who played music by running their fingers around the rims of glasses filled with water. Franklin worked with a glassblower in London to create a less cumbersome version of this instrument. Benjamin himself brought the armonica everywhere he traveled and played both popular music and his own compositions on it. Even well-known composers such as Mozart and Beethoven wrote songs for the instrument.

Despite its initial popularity, the armonica fell out of use in the 1820s after some controversies arose regarding its safety. Some players claimed that the instrument was harmful to their health. While Franklin continued to play the armonica with no ill effects, other players experienced cramps and dizziness and a listener in Germany reportedly died during a concert. There were also rumors that the sound it produced drove people into madness. As a result, the armonica was largely forgotten until recent years when it experienced a resurgence in popularity with a small but dedicated group of musicians.