The two writers to be presently cited are selected as illustrations of the truth that the possession of intellectual attainments in other directions does not insure against such gross errors as are about to be noticed, and the second, moreover, serves as a type of the compilations of the period, to which the reader may be referred for further instances. The reputation of Miss Harriet Martineau insured general attention to her "Letters on Mesmerism" (1845). Miss Martineau was cured of a long-standing illness by magnetic treatment, the operator being a noted mesmerist, Spencer T. Hall. The magnetizing process gave rise to peculiar sensations which were attributed to the action of the magnetic fluid. "My head has often appeared to be drawn out, to change its form according to the traction of my mesmerist, and an indescribable but exceedingly agreeable sensation of transparency and lightness through a part or whole of the frame has followed." Miss Martineau was thus made a convert to mesmerism, and initiated experiments of her own, finding in her maid, J., a somnambule of unusual powers. She maintained her health by following the prescriptions given by the somnambule, and the latter exhibited the many varieties of marvels with which we have become familiar. The spontaneous or suggested utterances of the somnambule upon matters relating to her exalted condition were unquestioningly accepted. "Do the minds of the mesmerist and the patient become one?" "Sometimes, but not often."--"Is it, then, that they taste, feel, etc., the same things, at the same moment?" "Yes."--"Will our minds become one?" "I think not."--"What are your chief powers?" "I like to look up and see spiritual things; I can see diseases, and I like to see visions."--"Can the mind hear otherwise than by the ear?" "Not naturally; but a deaf person can hear the mesmerist when in the sleep; not anybody else, however."--"How is it that you can see without your eyes!" "Ah! that is a curious thing. I have not found it out yet."