Spirit materialisation. Illustration of a spirit materialising at a seance held during the 1870s. At centre is British psychic researcher Sir William Crookes (1832-1919). Crookes is holding up a phosphorus lamp to illuminate the scene and observe the spirit. This formed part of Crookes' research, in which he tried to discover whether the medium Florence Cook (at bottom left) and an apparition she produced, Katie King, were the same person. Apart from visually comparing the faces of Cook and King, Crookes also used photography to show that they were of a different height. This evidence convinced Crookes that King was actually a materialised spirit.