But it was not until the middle of the following century that researchers began to explore the possibilities of using a new power source and some new physical effects . Experiments by Joseph Swann in England and Farmer in the USA ( amongst others ) led to the development of a device in
which a tiny metal filament enclosed within a glass envelope was heated to incandescence by an electric current. This was the first electric light bulb - and it still bears more than a passing resemblance to the product found hanging from millions of ceilings all around the world