Describe the following lines in "Ode to a Nightingale."O for a draught of vintage! that hath been Cool'd a long age in the deep-delvèd earth,...

Keats, the narrator, is trying to become like the
nightingale. He considers the bird immortal because this nightingale reminds him of
nightingales he has read of throughout the history of literature and poetry. Since this
bird is linked to all other nightingales in history, it is as if the nightingale (and
all nightingales) is immortal.

Since Keats
cannot physically become the nightingale, he tries to create imagery and metaphors that
will verbally take him there. In other words, he is trying to write his way there. The
narrator is clearly trying to be like the nightingale, but why? He knows the nightingale
is not really immortal. But perhaps the nightingale believes he (the nightingale) is
immortal.

The narrator admires the beauty of the
nightingale's song and the beauty of nature in general. Keats often writes of his awe
for nature and the tragedy of being aware that he will die someday. When he dies, he
will no longer be able to appreciate nature's beauty.
So, the narrator admires
the nightingale's natural beauty but (and this is the key) he also envies the fact that
the nightingale does not have to face the constant conscious awareness of mortality
(death).

Keats, the narrator, a human, does have to live
with thoughts of his own mortality. In the third stanza, he writes about
this:

Fade
far away, dissolve, and quite forget
What thou amongst the leaves has never
known,
The weariness, the fever, and the fret
Here, where men sit
and hear each other groan;
Where palsy shakes a few, sad, last gray hairs;
(21-25)

In the stanza
(2nd) which you asked about, the narrator is asking for a wine (vintage) so that he may
become (metaphorically) drunk enough to forget that he is mortal. Thus, he can become
more like the nightingale: full of beauty but no longer plagued by thoughts of death. He
is actually writing about being drunk enough to forget about the fact of death. Then he
can enjoy nature without the constant fear that he will someday lose the ability to
enjoy nature.

Also note that Hippocrene refers to a
fountain in Greek mythology which could provide poetic inspiration when consumed.