(c)
Sing, Heav'nly Muse, that, on the secret top
favours the idea that Milton, as most Elizabethans certainly did, thought "Heaven" a monosyllable. But compare line 297—
On Hea|ven's a|zure; and | the tor|rid clime.
(d) Note, too, words like "ominous," "popular," "delicate," printed without attempt to apostrophate, though the middle syllabic makes a trisyllabic foot.
Again, consider the comparative euphony of the following lines:
(e)
Of glo|ry̆ ŏbscūred | ăs whēn | thĕ Sūn | nĕw rīsĕn,
or
Of glor|y̆obscūred, | etc.