The physical philosopher (and we are all physical philosophers, whatever else we may be) naturally asks, when he is told that this or that person has seen a ghost, “Will you show me the ghost?” Sometimes he is informed that if he sleeps in the haunted room he will be quite satisfied. Sometimes he does, and isn’t—sometimes he does, and _is_; when he _is_, like a wise man he is apt to keep what he has seen (as Johnson said every man did his religion) to himself. Perhaps he may have been in the habit of laughing at ghosts and sneering at people who believed in them, and doesn’t want to eat his own words. Perhaps he resembles the man who said “he did not believe in ghosts, but was very much afraid of them;” or, perhaps, he had no taste, after making a full confession about what he may have seen, for the retort courteous, that he was probably a fool or a liar—or both. Anyhow, the physical philosopher might next inquire, Did several people see the ghost at once, or independently at different times? Is there reason—that is to say—to suppose the ghost was really an objective (external to the spectator) or merely a subjective hallucination? A very reasonable inquiry. “Photograph me a ghost; chemicals have no fancies, plates don’t get nervous, and lenses tell no lies!” Good. So we proceed to get a medium into the studio; we photograph away, and a ghost comes out behind the medium! “Ah! but did you examine the plate before it was slipped in?” “No.” “Then the plate was cooked; the ghost was already on it.” “Try again.” This time you bring your own plate; but again comes a ghost. “Ah! but did you change the screen behind you—shift it, or put your own screen?” “No.” “Well, the ghost was in chemicals on the screen.” So next time you remove the photographer’s screen, and put your own, and bring your own plate, too; but again comes a ghost. “Ah! but did you examine the inside of the camera? Did you watch the developing process? Did you watch your plate from beginning to end? Nay, did you spy everything—windows, &c.—outside thoroughly? A ghost might be shot on to the exposed camera. Did you allow any one to dress up in a sheet behind you, and do the partial exposure trick?” Well, next time you take every precaution, and if still you get a ghost, “that gives to reflect,” as the French say; so let us reflect a little. _“AUTHENTIC” GHOST PHOTOS._