e
Harmonious numbers; as the wakeful bird
Sings darkling, and in shadiest covert hid
Tunes her nocturnal note."

This is something more precise than a mere poetical allusion to his
blindness, and the inference is strengthened by the anecdote that when
"his celestial patroness" "Deigned nightly visitation unimplored," his
daughters were frequently called at night to take down the verses, not
one of which the whole world could have replaced. This was as it should
be. Grand indeed is the thought of the unequalled strain poured forth
when every other voice was hushed in the mighty city, to no meaner
accompaniment than the music of the spheres. Respecting the date of
composition, we may trust Aubrey's statement that the poem was commenced
in 1658, and when the rapidity of Milton's composition is considered
("Easy my unpremeditated verse") it may, notwithstanding the terrible
hindrances of the years 1659 and 1660, have been, as Aubrey thinks,
completed by 1663. It would still require mature revision, which we know
from Ellwood that it had received by the summer of 1665. Internal
evidence of the chronology of the poem is very scanty. Professor Masson
thinks that the first two books were probably written before the
Restoration. In support of this view it may be urged that lines 500-505
of Book i. wear the appearance of an insertion after the Restoration,
and that in the invocation to the Third Book Milton may be thought to
allude to the dangers his life and liberty had afterwards encountered,
figured by the regions of nether darkness which he had traversed as a
poet.

"Hail holy Light!...
Thee I revisit now with bolder wing,
Escaped the Stygian pool, though long detained
In that obscure sojourn, while in my flight
Through utter and through middle darkness borne."

The only other passage important in this respect is the famous one from
the invocation to the Seventh Book, manifestly describing the poet's
condition under the Restoration:--

"Standing on earth, not rapt above the pole,
More safe I sing with mortal voice, unchanged
To hoarse or mute, though fallen on evil days,
On evil days though fallen and evil tongues;
In darkness, and with dangers compassed round,
And solitude; yet not alone, while thou
Visitest my slumbers nightly, or when morn
Purples the east. Still govern thou my song,
Urania, and fit audience find, though few.
But drive far off