"Spirit photography, so called, has of late been asserting its existence in such a manner and to such an extent as to warrant competent men in making an investigation, conducted under stringent test conditions, into the circumstances under which such photographs are produced, and exposing the fraud should it prove to be such, instead of pooh-poohing it as insensate because we do not understand how it can be otherwise--a position that scarcely commends itself as intelligent or philosophical. If, in what follows, I call it 'spirit photography' instead of psychic photography, it is only in deference to a nomenclature that extensively prevails.... I approach the subject merely as a photographer." Mr. Traill Taylor then gives a history of the earlier manifestations of "Spirit Photography," and goes on to explain how striking phenomena in photographing what is invisible to the eye may be produced by the agency of fluorescence. He quotes the demonstration by Dr. Gladstone, F.R.S., at the Bradford Meeting of the British Association in 1873, showing that invisible drawings on white cards have produced bold and clear photographs when no eye could see the drawings themselves. Hence, as Mr. Taylor says, the photographing of an invisible image is not scientifically impossible. Mr. Taylor then proceeds to describe some personal experiments. He says: "For several years I have experienced a strong desire to ascertain by personal investigation the amount of truth in the ever-recurring allegation that figures other than those visually present in the room appeared on a sensitive plate.... Mr. D., of Glasgow, in whose presence psychic photographs have long been alleged to be obtained, was lately in London on a visit, and a mutual friend got him to consent to extend his stay in order that I might try to get a psychic photograph under test conditions. To this he willingly agreed. My conditions were exceedingly simple, were courteously expressed to the host, and entirely acquiesced in. They were, that I for the nonce would assume them all to be tricksters, and to guard against fraud, should use my own camera and unopened packages of dry plates purchased from dealers of repute, and that I should be excused from allowing a plate to go out of my own hand till after development unless I felt otherwise disposed; but that as I was to treat them as under suspicion, so must they treat me, and that every act I performed must be in the presence of two witnesses; nay, that I would set a watch upon my own camera in the guise of a duplicate one of the same focus--in other words, I would use a binocular stereoscopic camera and dictate all the conditions of operation....