In _Abercromby on the Mind_ we read an account of the observations made by a gentleman who was the victim of illusions during the whole of a pretty long life. If he met a friend in the street, he was unable to tell at first whether he saw a real human being or only a phantom. By close examination he could detect a difference between the real person and the creature of his imagination, the features of the former being sharper and more defined than those of the phantom; but in general he was obliged to test the reality of the figure he saw by the senses of touch and hearing. He was able, by concentrating his thoughts upon the appearance of any friend, to call up his image; a power which extended even to scenes that he had witnessed. Although he could produce these hallucinations at will, he was powerless in making them disappear; and when once he succeeded in calling forth these creatures of his imagination, he never could tell how long the delusion would last. This gentleman was in the prime of life, a good man of business, and otherwise in a perfect state of mental and bodily health. A member of his family possessed the same faculty, but in a minor degree. In 1806, General Rapp, when returning from the siege of Dantzic, having occasion to speak to the Emperor Napoleon, walked into his private room without being announced, and found him in such a profound state of abstraction, that he remained for some time unperceived by his imperial master. The General, seeing him thus perfectly motionless, fancied he must be ill, and purposely made a slight noise. Napoleon instantly turned his head, seized the General by the arm, and pointing upwards, exclaimed, “Do you see it up there?” The General, hardly knowing what to say, remained silent; but the Emperor repeated his question, and he was obliged to reply, that he saw nothing. “What,” said the Emperor, “you don’t see anything? You don’t see my star shining before your eyes?” And becoming more and more animated, he went on to say, that the mysterious visitor had never abandoned him, that he saw it throughout all his great battles, that it always led him onward, and that he was never happy but when he was gazing at it.