Any one who has been thinking much for several days about a problem is likely to wake up with the thought that he has dreamed a solution of it, though unfortunately the solution has not remained in his memory. It seems as if a communication has been made to him during sleep. I have discussed dream life with many men engaged in serious work, and practically all of them confess to such experiences. Preoccupation of mind with a subject during the waking hours leads to at least some occupation of mind with the same subject during sleep. This unconscious occupation must often require rather strenuous attention, exhausting nutrition, using up nerve force and hampering the rest that is so important for tired human nature. [Footnote 17]

[Footnote 17: A number of poetic products of dreams are in our literature, some of them interesting for more than their curious origin. Dr. S. Weir Mitchell, in his latest volume of poems, "The Comfort of the Hills," made an interesting contribution to the psychology of dreams by publishing two poems which were composed by him while asleep. The little poem, "Which?" has all the curious alliterativeness and frequent rhyme that is so likely to be noted in expressions that come during sleep, or just as we awake. The other is more like a somnambulistic effort. What we might suggest here is that the habit of poetizing during sleep would surely be dangerous to any one less eminently sane than their author. We give them as curious examples that will interest patients who complain that their dreams are too vivid.

For further details on this subject, see the chapter on Dreams.

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 DuprÉ, 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.]
It is interesting both as psychological fact and as showing how, sleeping and waking, his work was ever present with him. He had been for two weeks striving to decipher the somewhat obscure impression of a fossil fish on the stone slab in which it was preserved. Weary and perplexed he put his work aside at last, and tried to dismiss it from his mind. Shortly after, he waked one night persuaded that while asleep he had seen his fish with all the missing features perfectly restored. But when he tried to hold and make fast the image it escaped him. Nevertheless he went early to the Jardin des Plantes, thinking that on looking anew at the impression he should see something that would put him on the track of his vision. In vain—the blurred record was as blank as ever. The next night he saw the fish again, but with no more satisfactory result. When he woke it disappeared from his memory as before. Hoping that the same experience might be repeated, on the third night he placed a pencil and paper beside his bed before going to sleep. Accordingly toward morning the fish reappeared in his dream, confusedly at first, but at last with such distinctness that he had no longer any doubt as to its zoological characters. Still half dreaming, in perfect darkness, he traced these characters on the sheet of paper at the bedside. In the morning he was surprised to see in his nocturnal sketch features which he thought it impossible the fossil itself should reveal. He hastened to the Jardin des Plantes, and, with his drawing as a guide, succeeded in chiseling away the surface of the stone under which the portions of the fish proved to be hidden. When wholly exposed, it corresponded with his drawing, and his dream, and he succeeded in classifying it with ease. He often spoke of this as a good illustration of the well-known fact that when the body is at rest the tired brain will do the work it refused before.

Hilprecht's Sleep Vision.—Quite as surprising a dream was that of Prof. Hilprecht, of the University of Pennsylvania. He had been trying for some time to decipher certain characters on ancient cylinders from the Orient. In spite of much hard mental labor he had been utterly unable to reach definite conclusions. In the midst of work on the subject he dreamt one night that a priest of the olden time appeared to him and read off the inscription that he had in vain been trying to decipher. Immediately after waking he told his wife of his dream and wrote down the interpretation that had thus been given. It was quite different from anything that he himself had obtained any hint of in his previous studies. When he got back to the inscription he found that this interpretation would satisfy the conditions better than any other, and there seemed no doubt that it represented the missing solution.{138}

Somnambulism.—These curiously vivid dreams are occasionally associated with somnambulistic phenomena. Sometimes very definite purposes, requiring careful adaptation of means to ends, are accomplished in the somnambulistic state, and yet the actions are completely forgotten. I have recently been consulted about a case in which a young woman, on a visit to a family, had been shown some pretty though not expensive jewels. Evidently the guest envied their possession, for she got up during sleep and took the jewels and hid them. There seems no reason to doubt her statement that she remembered nothing at all about the incident. The taking was not attributed to her. There had been previous experiences of the same kind with things belonging to this young woman's sister. Somnambulism represents a degree of unconscious cerebration that may have serious results. Combinations of intellectual work with somnambulism are not infrequent, though many of the stories that are told are exaggerated. Some of them are authenticated. Ribot has a typical example of intellectual accomplishment, in a somnambulistic condition, that shows how far this may go:

A clear case of somnambulism was that of a clergyman, whom his wife saw rise from bed in his sleep, go to a writing table, and write rapidly for some minutes. This done he returned to bed, and slept on until morning. On awaking, he told her that in a dream he had worked out an argument for a sermon, of which he now retained no recollection whatever. She led him to the writing table, and showed him the written sheet upon which he found his argument worked out in the most satisfactory manner.