the 1000th part of a grain of arsenic to be carried through the sides of a gas tube in which pure water is hermetically sealed.” These and other requirements are stated by Mr. Crookes, together with further exposition of the principles of strict inductive investigation, as it should be applied to such an inquiry. A year after this he published an account of the experiments, which I described in a former letter, and added to his own testimony that of the eminent physicist and astronomer, Dr. Huggins and Serjeant Cox. Subsequently, that is, in the last number of the “Quarterly Journal of Science,” he has published the particulars of another series of experiments. I will not now enter upon the details of these, but merely state that the conclusions of Mr. Crookes are directly opposed to those of the Spiritualists. He positively, distinctly, and repeatedly repudiates all belief in the operations of the supposed spirits, or of any other supernatural agency whatever, and attributes the phenomena he witnessed to an entirely different organ, viz.: to the direct agency of the medium. He supposes that a force analogous to that which the nerves convey from their ganglionic centres to the muscles, in producing muscular contraction, may by an effort of the will be transmitted to external inanimate matter, in such a manner as to influence, in some degree, its gravitating power, and produce vibratory motion. He calls this the _psychic force_. Now, this is direct and unequivocal _anti_-spiritualism. It is a theory set up in opposition to the supernatural hypotheses of the Spiritualists, and Mr. Crookes’s position in reference to Spiritualism is precisely analogous to that of Faraday in reference to table-turning. For the same reasons as those above-quoted, the great master of experimental investigation examined the phenomena called table-turning, and he concluded that they were due to muscular force, just as Mr. Crookes concludes that the more complex phenomena he has examined are due to psychic force. Speaking of the theories of the Spiritualists, Mr. Crookes, in his first paper (July, 1870), says: “The pseudo-scientific Spiritualist professes to know everything. No calculations trouble his serenity; no hard experiments, no laborious readings; no weary attempts to make clear in words that which has rejoiced the heart and elevated the mind. He talks glibly of all sciences and arts, overwhelming the inquirer with terms like ‘electro-biologise,’ ‘psychologise,’ ‘animal magnetism,’ etc., a mere play upon words, showing ignorance rather than understanding.” And further on he says: “I confess that the reasoning of some Spiritualists would almost seem to justify Faraday’s severe statement—that many dogs have the power of coming to more logical conclusions.”