When Were Diving Helmets Invented?

Diving helmets were invented in 1823, by an Englishman called Charles Deane.  Interestingly, he did not actually set out to invent a diving helmet.  Instead he was working on a project to devise a smoke helmet, so that firemen would be safe when fighting a fire.
It was called a 'smoke helmet' and was made of metal.  However, it was far from successful.  Due to the fact that it was metal when used in a fire fighting scenario it actually heated up.  So the firefighters ended up being extremely hot and had to carry round a heavy metal which trapped the heat, leading quickly to exhaustion and de-hydration.  Which meant they would not wear it.
Disappointed by his lack of success, Deane was eager to re-coup the money which he had invested in the helmet and found out that it could be used underwater in salvage operations: and so the diving helmet was invented.