Eternity. is agian used to paint the afterlife as never ending and stagnant. the end result of the sailors journey is eternity

This is a drasctic change from the active life at sea they had been living, a life ffilled with storms , breakers,

and where he was unable to set down anchor.

Eternity is used agian as a measure of time In Becuase I could not stop for Death, Death's companion acknowledges the level of dormancy and lack of change when she states

"Since then 'tis centuries, and yet each
 Feels shorter than the day".

I first surmised the horses head

toward eternity