The story of Faust and Margherita is ended, but, in pursuance of his larger plan, already outlined here, Boito makes use of two scenes from the second part of Goethe’s drama to fill a fourth act and epilogue.  They tell of the adventure of Faust with Helen of Troy, and of his death and the demon’s defeat.  The “Night of the Classical Sabbath” serves a dramatic purpose even less than the scene on the Brocken, but as an intermezzo it has many elements of beauty, and its scheme is profoundly poetical.  Unfortunately we can only attain to a knowledge of the mission of the scene in the study with Goethe’s poem in hand and commentaries and Boito’s prefatory notes within reach.  The picture is full of serene loveliness.  We are on the shore of Peneus, in the Vale of Tempe.  The moon at its zenith sheds its light over the thicket of laurel and oleanders, and floods a Doric temple on the left.  Helen of Troy and Pantalis, surrounded by a group of sirens, praise the beauty of nature in an exquisite duet, which flows on as placidly as the burnished stream.  Faust lies sleeping upon a flowery bank, and in his dreams calls upon Helen in the intervals of her song.  Helen and Pantalis depart, and Faust is ushered in by Mefistofele.  He is clad in his proper mediaeval garb, in strong contrast to the classic robes of the denizens of the valley in Thessaly.  Mefistofele suggests to Faust that they now separate; the land of antique fable has no charm for him.  Faust is breathing in the idiom of Helen’s song like a delicate perfume which inspires him with love; Mefistofele longs for the strong, resinous odors of the Harz Mountains, where dominion over the Northern hags belongs to him.  Faust is already gone, and he is about to depart when there approaches a band of Choretids.  With gentle grace they move through a Grecian dance, and Mefistofele retires in disgust.  Helen returns profoundly disquieted by a vision of the destruction of Troy, of which she was the cause.  The Choretids seek to calm her in vain, but the tortures of conscience cease when she sees Faust before her.  He kneels and praises her beauty, and she confesses herself enamoured of his speech, in which sound answers sound like a soft echo.  “What,” she asks, “must I do to learn so sweet and gentle an idiom?” “Love me, as I love you,” replies Faust, in effect, as they disappear through the bowers.  Now let us turn to Goethe, his commentators, and Boito’s explanatory notes to learn the deeper significance of the episode, which, with all its gracious charm, must still appear dramatically impertinent and disturbing.  Rhyme was unknown to the Greeks, the music of whose verse came from syllabic quantity.  Helen and her companions sing in classic strain, as witness the opening duet:—­

  La luna immobile innonda l’etere d’un raggio pallido. 
  Callido balsamo stillan le ramora dai cespi roridi;
  Doridi e silfidi, cigni e nereidi vagan sul l’alighi.

Faust addresses Helen in rhyme, the discovery of the Romantic poets:—­