Benjamin Franklin, American scientist, inventor and statesman, shown here in his physics laboratory in Philadelphia. As well as his numerous scientific discoveries, Franklin was also one of the signatories of the US Declaration of Independence in 1776. As a scientist, he showed that lightning is electricity in a famous experi- ment in which he flew a kite carrying a metal key during a thunderstorm. This led to his invention of the lightning rod to protect buildings from lightning strikes. He also discovered the Gulf Stream ocean current, which carries warm water north to Europe. Amongst his other inventions were bifocal spectacles and a stove.