In 1917, Edward Clodd analyzed the mediumship of the trance medium Gladys Osborne Leonard and came to the conclusion that Leonard had known her séance sitters before she had held the séances, and could have easily obtained such information by natural means.[116] The British psychiatrist Charles Arthur Mercier wrote in his book Spiritualism and Sir Oliver Lodge (1917) that Oliver Lodge had been duped into believing mediumship by trickery and his spiritualist views were based on assumptions and not scientific evidence.[117]
Some scientists of the period who investigated spiritualism also became converts. They included chemist Robert Hare, physicist William Crookes (1832–1919) and evolutionary biologist Alfred Russel Wallace (1823–1913).[13][14] Nobel laureate Pierre Curie took a very serious scientific interest in the work of medium Eusapia Palladino.[15] Other prominent adherents included journalist and pacifist William T. Stead (1849–1912)[16] and physician and author Arthur Conan Doyle (1859–1930).[17]
A very large part is played by fraud in spiritualistic practices, both in the physical and psychical, or automatic, phenomena, but especially in the former. The frequency with which mediums have been convicted of fraud has, indeed, induced many people to abandon the study of psychical research, judging the whole bulk of the phenomena to be fraudulently produced.[55]
In September 1878 the British medium Charles Williams and his fellow-medium at the time, A. Rita, were detected in trickery at Amsterdam. During the séance a materialized spirit was seized and found to be Rita and a bottle of phosphorus oil, muslin and a false beard were found amongst the two mediums.[82] In 1882 C. E. Wood was exposed in a séance in Peterborough. Her Indian spirit control "Pocka" was found to be the medium on her knees, covered in muslin.[83]