how their delusions consisted of the ocular _spectra_ of their brain and the accelerated sensations of their nerves. BAYLE has conjured up an amusing theory of apparitions, to show that HOBBES, who was subject to occasional terrors, might fear that a certain combination of atoms agitating his brain might so disorder his mind as to expose him to spectral visions; and so being very timid, and distrusting his own imagination, he was averse at times to be left alone. Apparitions often happen in dreams, but they may happen to a man when awake, for reading and hearing of them would revive their images, and these images might play even an incredulous philosopher some unlucky trick. [Footnote A: CHARLES BUTLER has drawn up a sensible essay on "Mystical Devotion." He was a Roman Catholic. NORRIS, and Dr. HENRY MORE, and Bishop BERKELEY, may be consulted by the curious.] But men of genius whose enthusiasm has not been past recovery, have experienced this extraordinary state of the mind, in those exhaustions of study to which they unquestionably are subject. Tissot, on "The Health of Men of Letters," has produced a terrifying number of cases. They see and hear what none but themselves do. Genius thrown into this peculiar state has produced some noble effusions. KOTZEBUE was once absorbed in hypochondriacal melancholy, and appears to have meditated on self-destruction; but it happened that he preserved his habit of dramatic composition, and produced one of his most energetic dramas--that of "Misanthropy and Repentance." He tells us that he had never experienced such a rapid flow of thoughts and images, and he believed, what a physiological history would perhaps show, that there are some maladies, those of the brain and the nerves, which actually stretch the powers of the mind beyond their usual reach. It is the more vivid world of ideal existence.