100lx: Henry Gillard Glindoni – John Dee performing an experiment before Queen Elizabeth I.
When first painted, the painting showed Dee standing in a circle of human skulls, the accoutrement of practitioners of black magic. The painter later painted over the skulls. Over the years, chemical changes in the pigments have caused the overpaint to become transparent, so that at least five skulls are now (1992) visible: two of them can be seen on the ground behind Dee and another (on its side) is between him and the brazier.