[235.] her sad song mourneth, i.e. sings her plaintive melody. ‘Sad song’ forms a kind of cognate accusative.
[237.] likest thy Narcissus. Narcissus, who failed to return the love of Echo, was punished by being made to fall in love with his own image reflected in a fountain: this he could never approach, and he accordingly pined away and was changed into the flower which bears his name. See the dialogue between Mercury and Echo in Cynthia’s Revels, i. 1. Grammatically, likest is an adjective qualified adverbially by “(to) thy Narcissus”: comp. Il Pens. 9, “likest hovering dreams.”
[238.] have hid. This is not a grammatical inaccuracy (as Warton thinks), but the subjunctive mood.
[240.] Tell me but where, i.e. ‘Only tell me where.’
[241.] Sweet Queen of Parley, etc. ‘Parley is conversation (Fr. parler, to speak): parlour, parole, palaver, parliament, parlance. etc., are cognate. Daughter of the Sphere, i.e. of the sphere which is her “airy shell” (l. [231]): comp. “Sphere-born harmonious sisters, Voice and Verse” (At a Solemn Music, 2).
[243.] give resounding grace, etc., i.e. add the charm of echo to the music of the spheres.
The metrical structure of this song should be noted: the lines vary in length from two to six feet. The rhymes are few, and the effect is more striking owing to the consonance of shell, well with vale, nightingale; also of pair, where with are and sphere; and of have with cave. Masson regards this song as a striking illustration of Milton’s free use of imperfect rhymes, even in his most musical passages.
[244.] mortal mixture ... divine enchanting ravishment. The words mortal and divine are in antithesis: comp. Il Pens. 91, 92, “The immortal mind that hath forsook Her mansion in this fleshly nook.” The lines embody a compliment to the Lady Alice: read in this connection lines [555] and [564]. ‘Ravishment,’ rapture (a cognate word) or ecstasy: comp. Il Pens. 40, “Thy rapt soul sitting in thine eyes”; also l. [794].
[246.] Sure, used adverbially: comp. line [493], and ‘certain,’ l. [266].
[247.] vocal, used proleptically.