The most essential difference between the theatre which we are considering and that of the fifth century lay in the substitution of a tall and narrow stage for a low and comparatively deep one. This change was far more important than a mere change of material from wood to stone. The question naturally arises, what was the reason for the alteration? The answer is to be found in the fact that the Greek drama itself passed through a no less radical transformation at the same time. In the course of the fourth century it was gradually transformed from a choral to a non-choral drama. When we come to the third century we find that the chorus, which once played the chief part both in tragedy and comedy, had sunk into insignificance. It was often discarded altogether. When retained, it had nothing to do but to sing interludes between the successive acts. Its presence no more implied that the play was a choral play than the presence of the band in a modern theatre implies that the performance is an opera. The old intercourse between actors and chorus was a thing of the past.[429] The low deep stage was no longer necessary, to enable actors and chorus to converse together, or to supply room, when required, for the presence of the chorus by the side of the actors. Under these circumstances it would obviously be an advantage to make the stage as high as possible, in order to improve the view of the upper rows of spectators. The ancient theatres were of enormous size. At Athens, for example, the topmost tier of seats was 300 feet distant from the stage, and 100 feet above the level of the orchestra. In such a theatre, the higher the stage, the better would be the view of the majority of the audience. It was doubtless for this reason that the stage was raised to about ten or twelve feet in the course of the third century. At the same time its depth was necessarily diminished, in order that the spectators in the lowest rows might be able to see down to the end of it. The loss of depth was of no importance in the acting of a play, because of the practical exclusion of the chorus from the stage.