I have every wish to speak on matters of physiological experiment with the modesty befitting my comparative unfamiliarity with the subject. I have no difficulty in admitting all that Dr. Carpenter says, in his article on "Electro-biology and Mesmerism" (_Quart._, Oct., 1853), on the action of dominant ideas, whether original or suggested, in the production of the phenomena of somnambulism and mesmerism; but I hesitate as to the possibility of receiving in the form of an unconscious ideational change such a piece of information as this: "I have another sister besides those I am used to reckon"; and of its recovery, not as an image or sensation such as a dream might leave, but as an unequivocal assertion of a fact clothed in all its native confidence. The nerve modification, which I suppose the "ideational change" comes to, is here understood to play the part, not merely of a bell whose prolonged vibrations, when taken cognizance of, may more or less suggest the individual visitor, but of a photographic negative, set aside, indeed, and overlaid, but from which at any moment exact representations may be taken. This theory appears to me to belong to the category of those which, to borrow Dr. Carpenter's expression (art., p. 535), "cannot be accepted without a great amount of evidence in their favor, but which, not being in absolute opposition to recognized laws, may be received upon strong testimony, without doing violence to our common sense." I must add that I have met with no such evidence either in the _Quarterly Review_ or elsewhere. When we ask for instances, in which modern science is ordinarily so fertile, it is at least suspicious that the only at all adequate examples produced in the brilliant article, "Spiritualism and its Recent Converts" (_Quart._, vol. 131, 1871), are taken from the very spiritualistic phenomena under discussion. Let us, however, for the moment grant all that is expressly demanded on the score of unconscious cerebration, and then see how far it affords an adequate explanation of the phenomena of spiritualism. Of course, independent physical manifestations, such as the subcommittees report, fall entirely without the sphere of this explanation; and Faraday's ingenious machine for testing muscular action has no place where there is no contact of muscles. But what are we to say to communications such as the following (_Rep._, p. 195), made to Signor Damiani, at Clifton? He asked of the rapping table, "Who is there?" "Sister," was rapped out in reply. "What sister?" "Marietta." "Don't know you; that is not a family name. Are you not mistaken?" "No; I am your sister." He left the table in disgust, but afterwards joined in another séance at the same house. "Who are you?" he asks. "Marietta." "Again! Why does not a sister whom I can remember come?" "I will bring one." "And the raps were heard to recede, becoming faint and fainter, until lost in the distance. In a few seconds, a