A few detective stories could be classed with our last preceding type as well as with this. Those like F. R. Burton's suppressed prize contribution to a Western newspaper might be put under mechanical inventions; that is, all that contain, like his, a practicable theory. The report goes that Mr. Burton and a friend worked together and produced a story of bank robbers who overcame the time-lock device. So explicitly was the ingenious method written out that the editors decided not to publish it, convinced that if they spread the knowledge abroad no time-lock thereafter would be secure. "The Black Pearl" by Victorien Sardou, on the other hand, might be called a scientific-discovery detective tale. It perfectly combines the two elements--mystery and the astounding action of a nature phenomenon. Not all detective stories, however, are so dangerous or so interesting as these. Most, rather, are amusing or merely entertaining; but we class them in the ingenious group because of the effort at pure plot. There are many crude attempts at writing detective stories, and the cheap, ten-cent-novel kind disgusts persons of taste; but the popularity of the type attests its excellence. When in the hands of such men as Edgar Allan Poe and A. Conan Doyle, it yields an artistic short-story. "The Purloined Letter" and the "Adventures of Sherlock Holmes" are worthy of their fame. "The Murders in the Rue Morgue" and the "Mystery of Marie Rogêt" are not so pleasant, but are equally ingenious. Of course, the author of the ordinary tale of this type has the advantage over the real detective, since the author first creates the mystery before solving it. His ingenuity, therefore, will lie revealed in the construction of the crime which he pretends to be unearthing and explaining. Evidently, though, his process of mind can be no different from that of the actual analyzer, who must unravel what to him is a real mystery. He, too, if he is to succeed, must re-image the whole train of events, not as points or dots, but as vivid scenes. Thus only will both workers come at small incidents that are original and ingenious and essentially pertinent. It happened that Poe, in the story of Marie Rogêt, was acting the part of a real detective, since he was reasoning upon an actual mystery, the details of which had baffled the police. In his imaginary case he reinstalled the crime as he felt it must have taken place, and, strange to say--or rather not strange to say, for Poe had the qualities of more than a paper detective--the facts, by a woman's confessions later, were found to be exactly as Poe had imagined them, even in minor details. [Other stories of plot]