He's woken when a king - King Midas - and his soldiers come riding up. Midas has a special longing to see Dionysus and Silenus agrees to take him to see the god in exchange for the loan of a horse.
In stanza four, Mrs Midas ... a shaking hand. Alliteration is used to highlight the seriousness and reality of the situation when she witnesses the transformation of a glass into a golden chalice.