A gathering of people for the purpose of investigating or experiencing supernormal or psychic phenomena. In the past, seances were often called 'circles', because participants, called 'sitters', sat around a table in order to link hands, in the belief that this somehow boosted the psychic forces which encourage paranormal manifestations.
Generally, seances involve a medium who enters a trance-like state and contacts the spirit of someone who has died. The spirit then communicates with the gathering through the medium, either mentally, or directly using the medium's vocal chords. In the 19th century, seances were usually accompanied by physical manifestations, such as rappings, strange smells, levitation, and materialization.