Every Sanskrit play begins with a prologue or introduction, which regularly opens with a prayer or benediction (nandi) invoking the national deity in favour of the audience. Then generally follows a dialogue between the stage-manager and one or two actors, which refers to the play and its author, seeks to win public favour by paying a complimentary tribute to the critical acumen of the spectators, mentions past events and present circumstances elucidating the plot, and invariably ends by adroitly introducing one of the characters of the actual play. A Sanskrit drama is divided into scenes and acts. The former are marked by the entrance of one character and the exit of another. The stage is never left vacant till the end of the act, nor does any change of locality take place till then. Before a new act an interlude (called vishkambha or praveçaka), consisting of a monologue or dialogue, is often introduced. In this scene allusion is made to events supposed to have occurred in the interval, and the audience are prepared for what is about to take place. The whole piece closes with a prayer for national prosperity, which is addressed to the favourite deity and is spoken by one of the principal characters. The number of acts in a play varies from one to ten; but, while fluctuating somewhat, is determined by the character of the drama. Thus the species called natika has four acts and the farcical prahasana only one. The duration of the events is supposed to be identical with the time occupied in performing them on the stage, or, at most, a day; and a night is assumed to elapse between each act and that which follows. Occasionally, however, the interval is much longer. Thus in Kalidasa's Çakuntala and Urvaçi several years pass between the first and the last act; while in Bhavabhuti's Uttara-ramacharita no less than twelve years elapse between the first and the second act. Nor is unity of place observed; for the scene may be transferred from one part of the earth to another, or even to the aërial regions. Change of locality sometimes occurs even within the same act; as when a journey is supposed to be performed through the air in a celestial car. It is somewhat curious that while there are many and minute stage directions about dress and decorations no less than about the actions of the players, nothing is said in this way as to change of scene. As regards the number of characters appearing in a play, no limit of any kind is imposed.