Benjamin Franklin was born on January 17, 1706, making today his 305th birthday. Here is a list of things you may or may not have known sprang from this impossibly talented man's mind.
While it was only a redesign of an existing instrument, the crystallophone (which involved producing sound by fingering variously sized glass bowls) Ben Franklin is said to have considered the armonica his favorite invention of all. It quickly became popular in America and Europe—Marie Antoinette took lessons on the instrument as a child, and composers including Bach, Beethoven, and Strauss all made music for the armonica specifically. The instrument's popularity waned after the 18th century due to urban legends about the purported health risks it posed, but you'll still find youngsters running their fingers around the rims of wine glasses at kids' tables across the world today.
Why switch between two pairs of glasses when you can just wear one? Ben Franklin invented bifocals with both a near lens and a far one after his vision started deteriorating in his late 60s, though correspondence between some of Franklin's contemporaries suggest he had conceived of the idea several decades earlier.
Ben Franklin didn't invent electricity, but in the course of his experiments with the force of nature he did invent the lightning rod. He speculated that a cloud's electricity, when nearing an iron rod sharpened to a point, would "be drawn out of a cloud silently, before it could come near enough to strike." Years later Tesla would prove that Franklin's design actually ionized the air surrounding the rod, rendering it conductive, but hey, still good on Franklin for getting the ball rolling with lightning prevention back in 1749.
Most 18th century homes were heated by fireplaces that were inefficient on many fronts. They used a lot of wood, lost a lot of heat, and posed the risk of sending sparks into mostly wood-built homes. Ben Franklin figured there was a better way, and there was: The Franklin Stove, also known as the "circulating stove" and the "Pennsylvania fireplace," had two distinguishing features: a hollow baffle and an inverted syphon flue that drove more heat into the room instead of losing it up through the chimney. Franklin's stove sold poorly—his cold flue cooled the smoke too quickly—but his design became the basis for many of stoves that followed it.
Map of the Gulf Stream
One of Franklin's many roles, at some point in his awesome life, was that of U.S. Deputy Post Master General, and at one point he received a complaint that letters sent from Europe to America took several weeks longer to arrive than ones sent from the New World to the Old. After consulting with a Nantucket whaling captain, Franklin made the first map of the Gulf Stream, a quick current of warm water running north from the West Indies and east across the Atlantic. His suggestions for British sea captains were summarily ignored for years, but when they did eventually factor the Gulf Stream into their routes they managed to shave up to two weeks off their transit times.
The idea of measuring a distance travelled goes back to the Roman architect Vitruvius and is one that also was pursued by fellow polymath Leonardo Da Vinci, but Ben Franklin's simple odometer—invented to measure the milage travelled by his carriage during a five month Post Office inspection in his days as Post Master General—is the precursor to the modern automotive odometer. Franklin measured the circumference of his carriage wheel—13 and one-fifth feet—and designed a series of cogs that noted a distance of one mile after every 400 revolutions.