Analysis of A Presentiment

It seems a little word to say -
FAREWELL--but may it not, when said,
Be like the kiss we give the dead,
Before they pass the doors for aye?

Who knows if, on some after day,
Your lips shall utter in its stead
A welcome, and the broken thread
Be joined again, the selfsame way?

The word is said, I turn to go,
But on the threshold seem to hear
A sound as of a passing bell,
Tolling monotonous and slow,
Which strikes despair upon my ear,
And says it is a last farewell.