Naturally, the next step for Edison was paranormal extermination. During the early days of the 20th century, contacting the spirit world was all the rage and any jackass with a gypsy wig and/or monocle could make bundles of cash holding seances to bilk grieving families hoping to talk to a deceased loved one. And if there was one thing Edison loved, it was money.
After intentionally burning his finger to the point his fingerprint was erased, Edison noted the fingerprint grew back and triumphantly concluded that all human beings must be made of "immortal units" which cannot be destroyed, thus explaining the existence of ghosts. He set about creating a device that would trap these immortal units and allow them to be studied by the living.
Edison was incredibly secretive about the nature of his ghost hunting mechanism--not even a prototype was ever seen. Just about the only real detail anyone knows is that one of his assistants died while working on it, presumably because Edison wanted to test and see if it worked.