Who discovered Direct Current?

Thomas Edison used direct current in his electric power transmission in the 1800's.

This isn't very relevant, but it is "Quite Interesting"

From QI--Elephant in the Room: In 1903, Thomas Edison made a film called Electrocuting an Elephant, in which he used an alternating current to kill an elephant called Topsy. He used the film as a Propaganda film to destroy the reputation of alternating current, owned by Westinghouse, believing his direct current was safer. He tried to encourage people to call being electrocuted, "Westinghoused".