Edward Thomas - How at Once

How at once should I know,
When stretched in the harvest blue
I saw the swift's black bow,
That I would not have that view
Another day
Until next May
Again it is due?

The same year after year -
But with the swift alone.
With other things I but fear
That they will be over and done
Suddenly
And I only see
Them to know them gone.

Edward Thomas

http://www.poemhunter.com/poem/how-at-once/