The brothers were sons of Zephaniah Eddy and his wife Julia Maccombs, natives of Vermont. It was claimed that their family could be traced back to the Salem witch trials, and that they had a long history of psychic ability. Growing up on a small farm near Chittenden, Vermont, both brothers claimed to have exhibited strong psychic abilities from an early age. Both the sons took up mediumship and held séances, they claimed to perform ectoplasm materializations and communicate with spirit guides. William would work in a séance cabinet on occasion and his brother Horatio would sit outside a cloth screen where they would claim spirits would play musical instruments behind the screen.
In 1870, William and Horatio were living with their widowed mother Julia in Chittenden. There, the Eddy family opened a small inn, called the Green Tavern. In addition to lodging travelers, the Green Tavern was also the spot of regularly scheduled séances that the brothers put on for visitors from around the world.
A typical séance of the Eddy Brothers would have the audience gathered in the "circle" room at the tavern. One of the brothers would enter a special spirit box at the front of the room (essentially just a small room with a chair in it) and lapse into a deep trance, at which point the show would start. It was alleged that instruments would start playing music on their own, various noises could be heard and strange lights would be seen.
The Eddy brothers séance trick was exposed by the magician Chung Ling Soo. The trick involved a curtain that was put across the room, with musical instruments placed on a table inside the curtain space. Two members of the audience would be selected and enter the curtain. Horatio would grasp the audience sitter's left arm and the other sitter would grasp his right arm. To the audience outside the curtain, various musical instruments would be seen floating in the air above the top of the curtain and tapping the trio on the head. A hand would also come through the curtain and write a message on a slate held by William who was sitting outside the curtain. The trick was performed by Horatio evading control and releasing his hand. He would do this by various methods such as using a fake hand made from a piece of heavy sheet lead which he would place in his left hand and grasp the audience sitter's arm. Horatio would quietly remove his real hand with the leaden hand remaining behind, giving the sense of touch that an actual hand was there. With his hands free Horatio would manipulate the instruments and perform the alleged supernatural phenomena.
The psychical researcher Hereward Carrington also revealed the sleight of hand tricks the Eddy brothers had used. Carrington described their tricks as "absurdly simple" and was surprised that people had been fooled by them.
- Raymond Buckland. (2005). The Spirit Book: The Encyclopedia of Clairvoyance, Channeling, and Spirit Communication. Visible Ink Press. pp. 120–121. ISBN 978-1-57859-213-5.
- Judith Joyce. (2010). Weiser Field Guide to the Paranormal. Weiser Books. p. 72. ISBN 978-1-57863-488-0.
- Chung Ling Soo. (1898). Spirit Slate Writing and Kindred Phenomena. Munn & Company. pp. 101–104.
- Hereward Carrington. (1907). The Physical Phenomena of Spiritualism. Herbert B. Turner & Co. pp. 193–195.
- Virtual Vermonter article.
- Carrington, Hereward (March 1919). "Taking the Spirits Out of Spiritualism: How mediums produce some of their many 'manifestations'". Popular Science. Vol. 94 no. 3. New York. p. 35. ISSN 0161-7370.