There are some who claim to have lived longer and more richly than their neighbours; when they lay asleep they claim they were still active; and among the treasures of memory that all men review for their amusement, these count in no second place the harvests of their dreams. - R. L. Stevenson, A Chapter on Dreams.

A more curious and much rarer type of dream than any of those that have hitherto been described, but which is attested by perfectly reliable witnesses, is what may be called the super-dream; in which the dream mind, working beyond its ordinary level of capacity, has actually solved problems that have defeated the efforts of the normal mind in its waking hours. The instance of Condor-cet, who in such a dream solved a mathematical problem, the answer to which he had vainly sought by day, has been often quoted; and Condorcet's experience was almost exactly repeated in the case of my father Nevil Story-Maskelyne. The mathematical problem that had baffled him came into the treatise on crystallography on which he was engaged. After working at it for many hours he was obliged to leave it unsolved and to go to bed. He fell into a deep sleep, and in the course of a long dream the answer to the problem came to him.

He often described this to me and told me how in an early hour of the morning he awoke and wrote down the solution that th6 dream had given him, and anxiously tested its correctness.

A friend writes of her very similar experience in solving mathematical difficulties in her sleep. "On more than one occasion when studying for examinations I worked for two or three days at a problem without arriving at the solution, and finally worked it in my dreams with such clearness that I was able to write down the correct result quite easily on awaking. On occasions during my schooldays the same thing used to happen, and if I met with very hard sums and riders I used to put pencil and paper by my bedside so as to be ready to write down the answer if it came to me in my sleep" Henri Fabre, in his "Souvenirs Entomologiques," explains that sleep in his case was often a state which did not suspend the mind's activity but actually quickened it, and in sleep he was able at times to solve mathematical problems with which he had struggled by day. "A brilliant beacon flares up in my brain, and then I jump from my bed, light my lamp and write down the solution the memory of which would otherwise be lost; like flashes of lightning these gleams vanish as suddenly as they appear".

These cases, though uncommon, are not isolated ones; other equally reliable witnesses have told of their similar experiences; and though these seem specially striking when the problems grappled with by the dream mind are the problems of such an exact science as mathematics, there is nothing in their occurrence that is out of harmony with what we know, or with what the latest researches of science teach us, about the mental faculties in the dream state. Reason is, we believe, continually at work in dreams, and we know that in this state imagination works with greatly increased powers. Imagination is an essential element in the attainment of any great intellectual result; and progress in mathematical knowledge, as in all scientific research, has been largely due to "provisional explanations constructed by the imagination, such explanations being framed in accordance with known facts." One great difference between these "super-dreams" and the ordinary dream is that a sufficiently clear remembrance of essential facts is carried over into the dream state to enable the dream reason to draw correct inferences, whereas in most dreams it has to work on more or less insufficient data and consequently often comes to wrong conclusions.

Armed with the necessary facts, reason in the super-dream works correctly and powerfully, and at the same time imagination supplies the other essential element that the thinker needs. Thought alone is not sufficient for most operations of the mind; imagination is also required. In every case of the kind that I have met with, the solution that has thus been arrived at in the dream seems to the dreamer not to be the product of his own reasoning powers, but to be a conclusion arrived at independently of himself, like a light flashed on to his mind from without, illuminating the difficulty that had seemed hopeless to his normal mind by day. This type of dream, with its strange faculty of insight or intuition, has been realised perhaps more often by men of letters than by men of science, although it must be in any case a rare experience. The dream in which Coleridge composed "Kubla Khan" may possibly be looked upon with some doubt, because in his case sleep was at times induced and influenced by opium, but there seems no reason to question the fact that the conception of the poem came to him in a dream, and that a part of it, at any rate, was written down from memory directly afterwards. Various instances of creative dreams have been related.

A striking example of an original and very dramatic story which was entirely the creation of a dream was told me lately by a writer who has attained a distinguished place among modern novelists. At the time when the dream occurred he was engaged on a book which was absorbing all his time and thoughts; about two-thirds of this had already been written, and it was making steady progress to completion, when one night he experienced a dream of extraordinary force and vividness. In this dream a story of a most dramatic nature was partially unfolded, and on following nights it was continued and completed. He dreamed and re-dreamed the story. The whole plot, the scenes of the drama and its characters, were so clearly realised, and made upon the dreamer so insistent an impression, that he could not free himself from the memory of them; they came between him and his other work, and he was at last obliged to lay this on one side until he had fully written down the dream story. He is, he explained, a rather slow worker, attaining the effects that he seeks by dint of patient care, but when he began to write down the dream it seemed to be like a tale that was told to him rather than a thing of his own creation.