The next writer in the order of development is Edgar Allan Poe, whose _Berenice_ appeared in 1835. With it the short-story took definite form. Poe's contribution is structure and technique; that is, he definitely introduced the characteristics noted in the definition--unity, compression, originality, and ingenuity. With almost mathematical precision he sets out to obtain an effect. To quote from his before-mentioned review of Hawthorne his own words which are so definite as almost to compose a formula of his way of writing a short-story and are so thoughtful as to be nearly the summary of any discussion of the subject: "A skillful literary artist has constructed a tale. If wise, he has not fashioned his thoughts to accommodate his incidents; but having conceived, with deliberate care, a certain unique or single effect to be wrought out, he then invents such incidents--he then combines such events--as may best aid him in establishing this preconceived effect. If his very initial sentence tend not to the out-bringing of this effect, then he has failed in his first step. In the whole composition there should be no word written of which the tendency, direct or indirect, is not to the one preëstablished design. And by such means, with such care and skill, a picture is at length painted which leaves in the mind of him who contemplates it with a kindred art a sense of the fullest satisfaction. The idea of the tale has been presented unblemished because undisturbed; and this is an end unattainable by the novel." It is to be noted that Poe roused interest in his effect by the method of suspense, that is, by holding back the solution of the plot, by putting off telling what the reader wants to know, though he continually aggravates the desire to know by constant hints, the full significance of which is only realized when the story is done. His stories are of two main classes: what have been called stories of "impressionistic terror," that is, stories of great fear induced in a character by a mass of rather vague and unusual incidents, such as _The Fall of the House of Usher_ (1839) and _The Pit and the Pendulum_ (1843); and stories of "ratiocination," that is, of the ingenious thinking out of a problem, as _The Mystery of Marie Rogêt_ (1843). In the latter type he is the originator of the detective story.