Dr's Casebook: Benjamin Franklin was a remarkable inventor...

I was over in New York last month and saw the most incredible fireworks display on the Hudson River to celebrate July 4, Independence Day. There was a real festival atmosphere on the streets, and skyscrapers, including the Empire State Building, were illuminated in red white and blue.

Dr Keith Souter writes: One of the signatories of the Declaration of Independence was Benjamin Franklin, who is regarded as one of the founding fathers of the United States and one of the most influential intellectuals of the 18th Century. I had researched him a few years ago for a book I was writing on the history of medicine. He was a remarkable polymath who was a writer, scientist, printer, newspaperman, inventor and politician.

He was a lifelong avid swimmer and at the age of 11 years he made his first invention, which he wrote about in an essay he titled The Art of Swimming. These were swimming flippers. In the essay he describes making two ten-inch long palettes with a hole for the thumb in each, which allowed him to fairly plough through the water.

Little was known about electricity in the 18th Century. Franklin was fascinated by the phenomenon and wanted to prove that lightning was a form of electricity. On a June afternoon in 1752 a thunderstorm in Philadelphia gave him the opportunity to conduct an experiment. He flew a kite attached to a house key, with a silk string leading to a Leiden jar, which was able to store electrical charge. Although the legend goes that lightning struck the kite, the silk actually picked up electrical charge and he was able to collect the charge in the Leiden jar.

Significantly, from this he invented the lightning rod, the use of which has protected buildings from lightning all around the world.

His older brother suffered from kidney stones and had to undergo a daily ritual of catheterising himself with a metal catheter. Benjamin designed a flexible catheter consisting of linked tubes of silver, which gave his brother and many thousands of

people relief until rubber catheters were produced.

In advancing age his eyesight deteriorated and rather than having to change spectacles, he invented bifocals. A simple invention that has benefited so many people ever since. Remarkably, he never patented any of his inventions, as he thought they should be available for all.