In structure there is a notable advance over preceding plays, accomplished apparently in part through deliberate intent. The first act with its account of Iago's craft and the marriage is a distinct introduction. The remaining four acts present a practically continuous action, confined to Cyprus and representing about thirty-six hours. Moreover, by a skillful ambiguity, which Christopher North called "the double clock," Shakespeare, while securing this rapid and uninterrupted process of time, has succeeded in conveying an impression of protracted intrigue and slowly-developing motives. Thus, without lessening the variety and importance of the events and emotions, he gains, by a closer observance of unity than in the other tragedies, a greater degree of theatrical illusion and of dramatic intensity. Again, "Othello" technically is noticeable among the tragedies for its relinquishment of many current methods. It is neither a chronicle history nor a Senecan tragedy. There is no presentation of history and little of court ceremonies. There are no battles, no long exposition, no spectacles, no ghosts, no insanity, and almost no comedy. It has few persons and virtually a single action. The underplot is subordinated and closely united to the main action, and there are no delays and new excitements between crisis and catastrophe as in "Hamlet" and "Lear." Nowhere else in Shakespeare is the progress of character, emotion, and deed toward the final event so consecutive and so uninterrupted. This advance in coherence and proportion seems due less to the contributing causes just enumerated than to the explanation of action by character. Accept the unbelievable malignity of Iago--and you do accept it before you have proceeded far--and every step of the appalling chain of intrigue seems a natural outcome of the motives of the persons before us.