The "Ring of the Nibelung" consists of four music-dramas--"Das Rheingold" (The Rhinegold), "Die Walküre" (The Valkyr), "Siegfried," and "Götterdämmerung" (Dusk of the Gods). The "books" of these were written in inverse order. Wagner made a dramatic sketch of the Nibelung myth as early as the autumn of 1848, and...