 He was a critic of spiritualism and attributed mediumship to suggestion and sleight of hand tricks.He explained the behavior of mediums as symptoms of hypnosis, hysteria, catalepsy and ectasy.His book "The Physics and Physiology of Spiritualism" (1871) is an early text on anomalistic psychology and was revised into a larger edition "Spiritualism and Allied Causes and Conditions of Nervous Derangement" (1876).