It is only fair, at the outset, to state that Mr. Crookes is not what is called “a spiritualist.” This I infer, both from what he has published and from conversation I have had with him on the subject. He has witnessed some of the “physical manifestations,” and, while admitting that many of these may be produced by the jugglery of impostors, he has concluded that others cannot be thus explained; but, nevertheless, does not accept the spiritual theory which attributes them to the efforts of departed human souls. He suspects that the living human being may have the power of exerting some degree of force or influence upon bodies external to himself—may, for instance, be able to counteract or increase the gravitation of substances by an effort of the will. He calls this power the “psychic force,” and supposes that some persons are able to manifest it much more powerfully than others, and thus explains the performances of those “mediums” who are not mere impostors. There is nothing in this hypothesis which the sternest, the most sceptical, and least imaginative of physical philosophers may not unhesitatingly investigate, provided some first-sight evidence of its possibility is presented to him. We know that the Torpedo, the Gymnotus, the Silurus Electricus, and other fishes, can, by an effort of the will, act upon bodies external to themselves. Faraday showed that the electric eel exhibited some years ago at the Adelaide Gallery was able, by an effort of its will, to make a magnetic needle suddenly turn thirty degrees aside from its usual polar position; that this same animal could—still by an effort of will—overpower the gravitation of pieces of gold leaf, cause them to be uplifted and outstretched from their pendent position, could decompose iodide of potassium, and perform many other “physical manifestations,” simply by a voluntary nervous effort, and without calling in the aid of any souls of other departed eels.