The modern psychological explanation of all this would be that in his many hours of searching through the books he had, though without being in the least aware of it, gradually brought together the data necessary to the solution of his problem; and that in this case this happened to be first definitely formulated in his mind while he slept, thus giving rise to the dream that caused him such astonishment. Or he might from the outset have subconsciously been aware of the cause of his error, but without being able to profit from the knowledge until a favouring condition in sleep permitted its emergence above the threshold of his consciousness. Now, suppose that instead of being a business man he had been a novelist, artist, or musician, and had been preoccupied with some special or general problem peculiar to his art. If in that event he had had a dream in which was presented to his sleeping consciousness a plot or subject or theme, which, being afterward given permanent form on paper or canvas, proved to have the qualities of a “work of genius,” would it not be logical to infer that precisely the same mental processes were operant in the second instance as in the first, the only difference being in the character of the product? This is what, from their own statement, has happened to not a few men of high achievement. Coleridge’s poem “Kubla Khan” was a dream composition. So was the sonata by which the composer Tartini is best known, and to which he appropriately gave the name of “The Devil’s Sonata,” in recognition of the fact that he owed it to a dream of selling his soul to the devil, and being rewarded by hearing the latter play on a violin the music out of which grew what Tartini himself regarded as his best piece of work. Benjamin Franklin was another man of genius who gained something from his dreams, as was Condillac. But the most striking illustration is afforded by Robert Louis Stevenson, whose marvellous “Doctor Jekyll and Mr. Hyde” was only one of several novels and stories that he conceived in dreams. Stevenson, it is worth adding, in his delightful “Chapter on Dreams,” frankly recognises and acknowledges the debt he owed to his subconsciousness, which, with characteristic felicity and whimsicality, he personified as “Brownies” and “little people.”