darkening visual light. Crookes' samples were made by Whitefriars, London, stained glass makers, and Chance Brothers, Birmingham. Spiritualism Crookes became interested in spiritualism in the late 1860s, and was most strongly involved around 1874–1875. Eric Deeson notes that Crookes' studies of the occult are related to his scientific work on radiometry in that both involved the detection of previously undiscovered forces. Crookes was possibly influenced by the death of his younger brother Philip in 1867 at 21 from yellow fever contracted while he was on an expedition to lay a telegraph cable from Cuba to Florida. In 1867, influenced by Cromwell Fleetwood Varley, Crookes attended a séance to try to get in touch with his brother. Between 1871 and 1874, Crookes studied the mediums Kate Fox, Florence Cook, and Daniel Dunglas Home. After his investigation, he believed that the mediums could produce genuine paranormal phenomena and communicate with spirits. Psychologists Leonard Zusne and Warren H. Jones have described Crookes as gullible as he endorsed fraudulent mediums as genuine. The anthropologist Edward Clodd noted that Crookes had poor eyesight, which may have explained his belief in spiritualist phenomena and quoted William Ramsay as saying that Crookes is "so shortsighted that, despite his unquestioned honesty, he cannot be trusted in what he tells you he has seen." Biographer William Hodson Brock wrote that Crookes was "evidently short-sighted, but did not wear spectacles until the 1890s. Until then he may have used a monocle or pocket magnifying glass when necessary. What limitations this imposed upon his psychic investigations we can only imagine." After studying the reports of Florence Cook, the science historian Sherrie Lynne Lyons wrote that the alleged spirit "Katie King" was at times Cook herself and at other times an accomplice. Regarding Crookes, Lyons wrote, "Here was a man with a flawless scientific reputation, who discovered a new element, but could not detect a real live maiden who was masquerading as a ghost". Cook was repeatedly exposed as a fraudulent medium but she had been "trained in the arts of the séance" which managed to trick Crookes. Some researchers such as Trevor H. Hall suspected that Crookes had an affair with Cook. In a series of experiments in London, England at the house of Crookes in February 1875, the medium Anna Eva Fay managed to fool Crookes into believing she had genuine psychic powers. Fay later confessed to her fraud and