Art in Dreams.--Many a painter testifies that as he slept interesting details have been added to his scheme for a picture. Mr. Huntington, who was for so long president of the National Academy, once told me that some of the arrangements of his famous picture, "Mercy's Dream" in the Corcoran Art Gallery at Washington, had come to him during sleep. Giovanni Dupre, the French sculptor, confessed that the ideas for his beautiful _pieta_ had practically all come to him in a dream. He had been thinking for a long time how he should arrange it, without allowing any of the ideas of sculptors whose treatment of the subject was well known to influence him too much, and had almost felt that it would be impossible to make anything individual. While deeply occupied with it one day he fell asleep, and when he awoke the whole scheme was clear. Mathematical Dreams.--Such phenomena of unconscious cerebration are not uncommon in the exact sciences. Some of the best examples of these {137} curious phenomena that we have are to be found in the history of them. We all know the stories of mathematicians who, occupied deeply with a problem which they have been unable to solve, have gone to bed still thinking about it, have slept deeply and, as they thought, dreamlessly, and yet they have waked in the morning to find by the bedside the problem all worked out in their own penciling--all accomplished during a somnambulistic state. Missing factors have been found in dreams; mistakes in the working out of problems have been clearly pointed out in dreams, so that, on awaking, the calculator could at once correct his calculations, and even serious errors have been thus corrected. Agassiz's Experience.--Some examples of these experiences in other sciences are striking. One that is likely to be impressive because it occurred in the experience of Professor Louis Agassiz, seems worth reporting. [Footnote 18] [Footnote 18: "Louis Agassiz, His Life and Correspondence," edited by Elizabeth Cary Agassiz, Houghton, Mifflin and Co., 1885.]