I maintain this merely to guard, so far as may be possible, against the accusations of prejudice which will doubtless be brought forward by some readers. _A priori_ considerations of this kind have their legitimate place, but it is on the relevant facts that our final decision must be based. On _all_ the relevant facts. This is the important point. It may be a “fact” that some great wise and eminent man states that he took such and such precautions, “never let the plates (or slides) out of his sight,” and so forth, but it is necessary to take into account, along with such statements as this, other facts about the psychology of deception, the reliability of witnesses, the potentialities of fraudulent methods and so forth which are usually ignored by enthusiastic devotees of the subject. One does not wish to be too dogmatic, there _may_ be such things as _bona fide_ spirit photographs, and when satisfactory evidence is forthcoming one will be very pleased indeed to make the _amende honorable_ and acknowledge one’s fault. But in view of the many methods of trickery which are available and the known incapacity of untrained observers to detect fraud the evidence at present available seems scarcely worthy of serious consideration. II.--HISTORICAL (C. VINCENT PATRICK) During the last half-century--that is, practically since the introduction of the photographic plate--various abnormalities have been reported in developed photographs. Some of these have appeared to reputable observers to be incapable of natural explanation, and have been eagerly seized upon by spiritualists as proof of survival after death--the sensitive emulsion being supposed to have recorded the presence of spirits, otherwise invisible. It is evident that a permanent photographic record, if its genuineness can be established, would stand almost alone as evidence of the presence of the spirit-forms described by clairvoyants. Various types of such photographic abnormalities must be distinguished: 1. “Thought photographs,” “dream photographs,” photographs of “psychic auras,” and the like. These are rarely distinct, and as they have little bearing on spirit phenomena they will not be discussed here. 2. Photographs taken of a visible spirit form. Such have been taken at _séances_: _e.g._, by Sir William Crookes, of Miss King’s “control,” Katie. The photographs taken recently at the Goligher circle should perhaps be included in this category. Similar experiments might, perhaps, be carried out in a “haunted house”--provided that one can be found which bears investigation.