Reasoning operations may be conducted in sleep. Mathematicians have in their slumbers solved problems which posed them when awake. The great metaphysician, Con-dillao, was sometimes enabled in his sleep to bring to a satisfactory conclusion speculations which in the day were incomplete. Cabanis tells us that Franklin so often formed correct and highly important conceptions of persons and political events in his sleep, as to have been inclined to view his dreams with superstitious reverence; while the real fact was, says Cabanis, that the philosopher's acute and sagacious intellect was operating even in his sleep.

Thus far, then, we see that the phenomena of dreams are regulated by the same laws of association or succession as those of waking thought; and the more closely we investigate the difference between these two classes of phenomena, the more clearly we shall perceive that many of the distinguishing characters are rather apparent than real.

Before, however, proceeding to point out in what respects the operations of the mind in sleep appear to differ from those in our waking hours, I shall adduce an example of a very interesting analysis, showing how the materials of the most heterogeneous and incongruous dreams may be traced to former and even recent experiences.

"I dreamed once," said Professor Maass, of Halle,* " that the Pope visited me. He commanded me to open my desk, and he carefully examined all the papen it contained. While he was thus employed, a very sparkling diamond fell out of his triple crown into my desk, of which however neither of us took any notice. As soon as the Pope had withdrawn, I retired to bed, but was soon obliged to rise on account of a thick smoke, the cause of which I had yet to learn. Upon examination, I discovered that the diamond had set fire to the papers in my desk, and burnt them to ashes."

"On the preceding evening," continues Professor Maass, "I was visited by a friend, with whom I had a lively conversation upon Joseph the 2nd's suppression of monasteries and convents. With this idea, though I did not become conscious of it in my dream, was associated the visit which the Pope publicly paid the Emperor Joseph at Vienna, in consequence of the measures taken against the clergy. And with this again was combined, however faintly, the representation of the visit which had been paid me by my friend. These two events were, by the subreasoning faculty, compounded into one, according to the established rule; - that things which agree in their parts, als0 correspond as to the whole. Hence, the Pope's visit to the Emperor was changed into a visit which was paid to me. The sub-reasoning faculty, then, in order to account for this extraordinary visit, fixed upon that which was the most important object in my room, viz., the desk, or, rather, the papers it contained. That a diamond fell out of the triple crown was a collateral association, which was owing merely to the representation of the desk. Some days before, when opening the desk, I had broken the glass of my watch which I held in my hand, and the fragments fell among the papers; hence no farther attention was paid to the diamond, as it was a representation of a collateral series of things. But afterwards, the representation of the sparkling stone was again excited, and became the prevailing idea; hence it determined the succeeding associations. On account of its similarity, it excited the representation of fire, with which it was confounded; hence arose fire and smoke. But in the event the writings only were burnt, not the desk itself; to which, being of comparatively less value, the attention was not at all directed."

* Quoted in Mr. Dendy's Philosophy of Mystery.

The most obvious difference between the sleeping and waking state has reference to the comparative vividness of present and past sensations; for while in the latter state ideas of sensational impressions are so faint as to be readily distinguished from things actually present (except in certain morbid conditions), in the former the reverse of this happens; perceptions fade away and former sensations are revived with an intensity that gives them the character of reality. That the intensity or vividness is not altogether dependent on the want of contrast with perceptions, I consider inferrible from the fact that actual outward sensations are often mingled with those which are revived. Slight sounds, feelings of heat and cold, frequently enter into the composition of our dreams, and by the laws of association suggest new scenes and characters in those nightly dramas. Exposure of the skin to cold may suggest all the scenery of Greenland, or the adventures of a Polar expedition. The faint light which penetrates the closed eyelid may give the idea of a conflagration, and so on. From this difference of degree, whether absolute or relative, in the vividness of ideas, it happens that the remembrances which occur in dreams are not felt to be remembrances. Whatever is then presented to the mind is not subjective but objective. Let it be a scene or transaction, it does not appear to us as a vision, but we take a part in it, and are involved mysteriously in its interests. Hence often the strangeness and incoherence of dreams. Our personal identity remains, and yet we are engaged in transactions that happened centuries ago. On this subject I may quote the experience of the English Opium Eater, related in his own peculiarly eloquent language. " I had been, in youth, and even since, for occasional amusement, a great reader of Livy, whom, I confess, that I prefer, both for style and matter, to any other of the Roman Historians; and I had often felt, as most solemn and appalling sounds, and most emphatically representative of the Roman people, the two words so often recurring in Livy, ' Consul Romanus,' especially when' the Consul is introduced in his military character. I mean to say that the words king, sultan, or regent, or any other titles of those who embody in their own persons the collective majesty of a great people, had less power over my reverential feelings. I had, also, though no great reader of history, made myself minutely and critically familiar With one period of English History, viz., the period of the Parliamentary War, having been attracted by the moral grandeur of some who figured in that day, and by the many interesting memoirs which survived those unquiet times. Both these parts of my lighter reading having furnished me often with matter of reflection, now furnished me with matter for my dreams. Often I used to see, after painting upon the blank darkness a sort of rehearsal whilst waking, a crowd of ladies, and perhaps a festival, and dances. And I heard it said, or I said to myself, ' These are English ladies from the unhappy times of Charles I. These are the wives and the daughters of those who met in peace, and sat at the same tables, and were allied by marriage or blood; and yet, after a certain day in August, 1642, never smiled upon each other again, nor met, but in the field of battle, and at Marston Moor, at Newbury, or at Naseby, cut asunder all ties of love by the cruel sabre, and washed away in blood the memory of ancient friendship.' The ladies danced, and looked as lovely as the court of George IV. Yet I knew even in my dream that they had been in the grave for nearly two centuries. This pageant would suddenly dissolve, and at a clapping of hands would be heard the heart-quaking sound of Consul Bomanus; and immediately came sweeping by, in gorgeous paludaments, Paulus or Marius, girt round by a company of centurions, with the crimson tunic hoisted on a spear, and followed by the alalagmos of the Roman legions."