What are they? Do they belong strictly to the domain of physics or of metaphysics? How nearly are they allied to insanity? May there not be a species of spiritual intoxication created by immaterial alcohol, producing, through the medium of the mind, the same bodily absurdities as your fluid alcohol produces through the directer agency of the body itself? How far can they be urged as extenuating or even defending misdemeanors and crimes? To guide me in my speculations, I run over a few cases that I can call to mind at once. There is a general fact, that no sooner have you mounted to a great eminence, than a mysterious impulse urges you to cast yourself over into space, and perish. Nearly all people feel this; nearly all conquer it in this particular; but some do not: and there may be a great doubt as to whether all who have perished from the tops of the monuments have been truly suicides. Then, again, with water: when you see the clear river sleeping beneath--when you see the green waves dancing round the prow--when you hear and see the roaring fury of a cataract--do you not as surely feel a desire to leap into it, and be absorbed in oblivion? What is that impulse but a perpetual calenture?--or may not the theory of calentures be all false, and the results they are reported to cause be in reality the results of morbid impulses? I have sat on the deck of a steamer, and looked upon the waters as they chafed under the perpetual scourging of the paddles; and I have been compelled to bind myself to the vessel by a rope, to prevent a victory to the morbid impulses that have come upon me. Are not Ulysses and the Sirens merely a poetic statement of this common feeling? But one of the most singular instances of morbid impulses in connection with material things, exists in the case of a young man who not very long ago visited a large iron manufactory. He stood opposite a huge hammer, and watched with great interest its perfectly regular strokes. At first it was beating immense lumps of crimson metal into thin, black sheets; but the supply becoming exhausted, at last it only descended on the polished anvil. Still the young man gazed intently on its motion; then he followed its strokes with a corresponding motion of his head; then his left arm moved to the same tune; and finally, he deliberately placed his fist upon the anvil, and in a second it was smitten to a jelly. The only explanation he could afford was that he felt an impulse to do it; that he knew he should be disabled; that he saw all the consequences in a misty kind of manner; but that he still felt a power within, above sense and reason--a morbid impulse, in fact, to which he succumbed, and by which he lost a good right hand. This incident suggests many things, besides proving the peculiar nature and power of morbid impulses: such things, for instance, as a law of sympathy on a scale hitherto undreamt of, as well as a musical tune pervading all things.