Sometimes these mental images are as vivid as the actual images, or even more vivid. Everybody has heard the story of Blake, who, when he was painting a portrait, only required one sitting, because subsequently he could see the model as distinctly as if he were actually sitting in the chair. Mrs. Haweis wrote to Mr. Galton that all her life she has had at times a waking vision of "a flight of pink roses floating in a mass from right to left," and that before her ninth year they were so large and brilliant that she often tried to touch them; and their scent, she adds, was overpowering. Much has been written regarding the remarkable feats of Zuckertort and Blackburn who can play as many as sixteen to twenty games of chess at once, and blindfolded. Of course the only way they can do this is by having in the mind a clear picture of each chess-board, with all the figures arranged in proper order. Mr. Galton says he has among his notes "many cases of persons mentally reading off scores when playing the pianoforte, or manuscripts when they are making speeches;" and he knows a lady, the daughter of an eminent musician, who often imagines she hears her father's playing. "The day she told me of it," he says, "the incident had again occurred. She was sitting in her room with her maid, and she asked the maid to open the door that she might hear the music better. The moment the maid got up the music disappeared." It is obvious that this case, like that of the eminent painter just referred to, borders closely on the hallucinations of the insane, and Blake _did_ become insane subsequently. But usually there is nothing abnormal or pathologic in the power of mentally recalling sights or sounds, and it would be well if everybody cultivated this power. Mr. Galton mentions an electrical engineer who was able to recall forms with great precision, but not color. But after some exercise of his color memory he became quite an adept in that, too, and declared that the newly-acquired power was a source of much pleasure to him.