There remains an important series of considerations that form an essential factor in the psychological comprehension of the phenomena of Spiritualism; this is the effect of bias and prepossession. When by one means or another a strong faith in the reality of spiritualistic manifestations has been induced; when the critical attitude gives place to a state of extreme emotional tension; when, perhaps, special griefs and trials give undue fervor to the desire for a material proof of life after death, of communion with the dear departed; when the convert becomes a defendant of the faith, anxious to strengthen the proofs of his own conviction,--then we have no longer mere unintentional lapses of observation and memory to deal with, but actual mental blindness to obvious fraud and natural explanations; then caution is thrown to the winds and marvels are reported that are the result of expectant attention and imagination, or of real illusion and hallucination. The blamelessness that may be conceded for one's mystification by conjuring performances cannot be extended to the present class of experiences; here it is not unusualness of external arrangements that forms the main factor in the deception, but the abnormal condition of the observer's mind. The materialization séances offer a sufficient example of this form of manifestation. To recognize a departed friend in the thinly disguised form of the medium is most naturally interpreted as a mark of weak insight or of strong prejudice. "Again and again," writes Dr. Furness, "men have led round the circles the materialized spirits of their wives and introduced them to each visitor in turn; fathers have taken round their daughters, and I have seen widows sob in the arms of their dead husbands. Testimony such as this staggers me. Have I been smitten with color-blindness? Before me, as far as I can detect, stands the very medium herself, in shape, size, form, and feature true to a line, and yet, one after another, honest men and women at my side, within ten minutes of each other, assert that she is the absolute counterpart of their nearest and dearest friend; nay, that she is that friend. It is as incomprehensible to me as the assertion that the heavens are green, and the leaves of the trees deep blue. Can it be that the faculty of observation and comparison is rare, and that our features are really vague and misty to our best friends? Is it that the medium exercises some mesmeric influence on her visitors, who are thus made to accept the faces which she wills them to see? Or is it, after all, only the dim light and a fresh illustration of _la nuit tous les chats sont gris_?" In the confessions of an exposed medium we read: "The first séance I held, after it became known to the Rochester people that I was a medium, a gentleman from Chicago recognized his daughter Lizzie in me after I had covered my small mustache with a piece of flesh-colored cloth, and reduced the