The presence of smoke may be considered as implying the existence of flame. 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 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, and not as offering a surmise from any knowledge of my own as to what is matter and what spirit, or the distinction between mind, spirit, and matter, for in truth I don’t know. I approach the subject merely as a photographer. Before I proceed, a few words on the origin of spirit photography may not be out of place. In March, 1861, W. H. Mumler, the principal engraver in the employ of Bigelow Bros. & Kennard, the leading jewellers of Boston, when whiling away an idle hour as an amateur photographer, had a form other than that of any one present developed on his collodion plate. He surmised that it arose from an image having been previously on the plate, and its having been imperfectly cleaned off. Subjected to a more thorough cleaning, the form again appeared more strongly marked than before, and he could offer no other explanation than the one given. It got noised abroad through the press that a spirit had been photographed, and although Mumler strove to suppress the misrepresentation, as he regarded it, yet he eventually succumbed to popular demand, and took two hours a day from his regular work, devoting them to photography. This he had to extend to the whole of each day, entirely discarding his regular profession. Many men of eminence sat to him, most of whom he did not know at the time. He seems to have encouraged his sitters in the adoption of such test conditions as they deemed satisfactory. The figures that usually appeared on the plate with the sitters were, if I rightly infer, those on whom the sitters’ minds had been set. That eminent portrait photographer, Mr. Wm. Black, of Boston, so well known all over the world as the inventor of the acid nitrate bath, undertook to investigate the _bonâ fides_ of Mumler’s methods. Through a friend who had just previously sat and obtained a figure, Black offered fifty dollars if Mumler would operate in his presence and obtain a picture. Invited to come, the acute Black critically examined camera, plate, dipper, and bath, and had his eye on the plate from the moment its preparation began until it was sensitised and locked in the dark slide, removing it himself from the camera, and carrying it into the dark room, where, on development, a figure of a man was seen leaning on B.’s shoulder.